Jeep Wrangler JK: How to Jump Start Your Battery

A dead battery can be easily fixed to get you home by jump starting it. Read on to learn how to revive your Jeep Wrangler.By Bassem Girgis – November 25, 2015

This article applies to the Jeep Wrangler JK (2007-Present).

If your Jeep Wrangler’s battery dies, it means you are not going anywhere; unless, of course, you have jumper cables. In order to jump your battery, you need another working vehicle and a jumper cable. The process of jumping the car should be classified as one of the easiest procedures you can do for your car, even easier than driving. The jumper cables borrow the charge from the working battery and charges your dead battery with just enough to get it started. Once it started, the alternator takes over and it recharges the battery. Sometimes you can recharge the battery by driving it for a little bit, but other times the battery will keep losing charge and you will have to replace it. Either way, jumping your car will allow you to get home instead of sitting around waiting for a tow truck. Read on to learn how to jump your Jeep Wrangler’s battery.

Figure 1. Jumper cables.

Materials Needed

  • Jumper cables
  • Working vehicle

Step 1 – Park face to face

Ask the assistant that will help you jump your car to park in front of your car, so both front bumpers are close to one another.

Figure 2. Park working car in front of your wrangler, facing each other.

Step 2 – Connect jumper cable

Open the hood on both cars. Connect the red cable to the working (running) car battery, then connect the other end of the red cable to the dead car battery.

Connect the black end of the cable to the working car battery, then connect the other black end to anything metal on the dead car, such as a bolt or bracket. The Wrangler will have a bolt designed for that under the hood, which is connected to the fender, so connect the black cable to it.

Figure 3. Connect negative cable to metal part.

Step 3 – Start your car

After you’ve hooked up the jumper cable, wait two to three minutes to allow the dead battery to recharge a little bit. Go in your car and start it. If you hear it trying to start (making clicking noises), let it recharge for five more minutes. If it starts, remove the negative cable from your car, then the negative from the assistant car, then the red cable from your car and finally the red cable from the assistant car.

Figure 4. Remove jumper cable.

Pro Tip

Be sure to take the long route home; the longer you drive, the more your battery will recharge.

Related Discussions

Jeep Wrangler JK: How to Replace Spark Plugs

Although many manufacturers are setting spark plug maintenance intervals near 100,000 miles, most enthusiast prefer to swap spark plugs more regularly. With spark plugs being relatively inexpensive, there are absolutely no downsides to replacing them as part of your regular maintenance regimen.By Joseph Coelho – November 17, 2015
Contributors: JeepFan & DSJeeps.

This article applies to the JK Jeep Wrangler (2007-Present).

Spark plugs are key components of any gasoline internal combustion engine. These small devices deliver electric current from the ignition coil(s) to ignite the air/fuel mixture inside of the combustion chambers. While spark plugs have proven to be quite robust and can last thousands of miles without the need for replacement, modern ignition systems have become quite sensitive to worn spark plugs. As spark plugs age, material from the electrode erodes and creates a larger gap for the voltage to jump across. Excessive gap has a tendency to place a strain on plug wires and ignition coils because this larger gap creates a higher resistance that must be overcome to create a spark. Spark plugs can also experience carbon buildup or insulator cracking, all of which can lead to engine misfiring or premature coil failure. Proper spark plug maintenance will ensure your ignition system is performing at its best to maximize combustion efficiency. This article will outline the procedure for replacing spark plugs in 2007 to present JK Jeep Wrangler models.

Materials Needed

  • 1/4″ and 3/8″ drive ratchets
  • 5/8″ spark plug socket
  • Various extensions (with one being at least 12″ long)
  • 8mm and 10mm sockets
  • T20 Torx driver
  • Torque wrench
  • Universal joint (swivel adapter)
  • Spark plug gapping tool or feeler gauges
  • Screwdriver
  • Dielectric grease
  • Anti-seize paste (optional)

Buying Replacement Spark Plugs

Generally, it is best to use OEM equivalent spark plugs in your Jeep. Aftermarket spark plugs can be less expensive, but they are often not made to the exacting standards as the spark plugs fitted from the factory. OEM plugs usually have a specific electrode design and material quality that is best suited for the engine. This is not to say there are no exceptions to this rule, but more often than not, individuals experience various engine and ignition system problems by using “exotic” aftermarket spark plugs instead of the tried and true originals.

  • 2007-2011: Champion Part #RE14PLP5
  • 2012+: Champion Part #RER8ZWYCB4

Figure 1. Quality spark plugs.

This how-to will cover spark plug replacement for both 2007 to 2011 3.8L EGH V6 engine and 2012+ 3.6L Pentastar V6 engine. For 2012+ models, the step-by-step instructions are below.

2007-2011 3.8L EGH V6 Engine

Step 1 – Replace bank 2 spark plugs

The 2007 to 2011 Wranglers equipped with the older 3.8L V6 engine allows for easy access to the driver’s side spark plugs.

  • Locate the three spark plug wires on the driver’s side of the engine. With a twisting motion, remove each spark plug wire from its companion spark plug. The spark plug wires are typically numbered to prevent them from getting mixed
  • Using a 3/8″ drive ratchet with an extension, universal joint adapter, and 5/8″ spark plug socket, remove the spark plugs.
  • Figure 3. A long extension and universal joint allows for easy reach of the spark plugs.
  • With the old spark plugs removed, prep the new spark plugs by checking the electrode gap with a gapping tool or feeler gauge. The spark plug gap specification for 2007 to 2011 models is .050″. Do not assume the plugs are ready to run out of the box. Improper spark plug gap can lead to rough running conditions.Figure 4. Checking and adjusting spark plug gap.
  • Place the new spark plug into the spark plug socket, making sure it is firmly held in place, and then lower it into its respective position in the cylinder head. Thread the spark plug carefully into the cylinder head and tighten it to 12 ft/lbs. Repeat for each plug.

  • Figure 5. A 3/8″ drive torque wrench can be used to tighten spark plugs.

Pro Tip

While Jeep does not suggest anti-seize paste on the threads of the spark plugs, some individuals opt to apply it, especially if your Jeep is used for off-road purposes.

  • Apply a thin film of dielectric grease to the spark plug boots before installing them onto the spark plugs. A small “click” can be heard and felt when the spark plug boot is firmly seated on the spark plug.

Step 2 – Replace bank 1 spark plugs

To gain access to the passenger’s side spark plugs, a few components must first be moved.

  • Disconnect the bank 1 spark plug wires (1, 3, 5) from the coil pack. It is recommended you label them if your wires are not already labeled.
  • Remove the spark plug wires from the passenger’s side spark plugs and remove the heater hose retaining strap from the valve cover. Also, remove the vent hose from the valve cover.
  • Remove the plastic spark plug wire tray from its mounting point on the valve cover. Maneuver the spark plug wires out from behind the engine and remove them from the engine bay. Pay close attention to their routing, as it will allow for proper installation after the new spark plugs are installed.

Jeep Wrangler JK: Battery Information

Choose the right battery for your Jeep and the conditions in which you drive it.By Jeffrey Smith – November 16, 2015

This article applies to the Jeep Wrangler JK (2007-Present).

There are many different batteries on the market that can be used in your Jeep Wrangler. How to sort through the myriad of choices can be a daunting task. With as many choices come just as many opinions from any Wrangler owner. How do you know which is the right battery for you? You can certainly narrow the field by looking at the size of battery that is standard for your Jeep. If you do not want to go into the extra work of modifying your engine compartment to fit one particular model over any other, then your choices are reduced considerably. Another factor to consider is the cold cranking amps, or CCA rating of a particular battery. Generally, the higher the CCAs, the more expensive the battery is. Also, another factor is warranties. Just because a battery has a one year warranty does not necessarily mean that you will be going through this process again in a short year; however, if you want to have a long life battery, you will most certainly need to purchase one with a longer warranty. Again, the longer the warranty, the higher the cost.

If you are fairly handy under the hood and skilled with a wrench, you may consider modifying your Wrangler for a dual battery system. This certainly extends the life of each battery and virtually guarantees that you won’t be stranded and have that extra reserve to use to get yourself to a shop for replacement without being towed there. If that is not an option you need, then consider these main components of a replacement battery to help make the right choice for your application.

Component Breakdown

Cold Cranking Amps (CCA)

The CCA is predominantly listed on each battery. It is crucial that you get a battery with enough CCA for the environment in which you live. Wrangler owners in warmer climates, such as Texas or southern Florida, can get by with lower CCA values than those in Main or Canada. You don’t want to be left stranded in the dead of winter with a new battery that has too low CCAs to get your Jeep running. Batteries with very high CCAs are often referred to as deep cycle batteries, and you may have troubles finding such batteries that are the correct size for your Jeep. The CCA rating of a battery should be the most important aspect in choosing the battery for your Wrangler.

Figure 1. Capacity definitions of any given battery.

Figure 2. The need for higher CCA is crucial in very cold climates.

  • Figure 3. Each battery’s CCA will be listed on a sticker.


Even among the same brand of battery comes a myriad of sizes. For Jeep JK Wranglers from 2007 to 2011, the OEM battery size was a group-34. From 2011 and on, they changed it to a group-91, which wouldn’t be so bad; however, they reversed the posts when they made the change for whatever reason. So while the size may fit, the cables will not reach without some significant modifications. Be sure to get the right size fitment, along with the correct terminal placements on the battery that you choose.

Figure 4. Batteries also come in many sizes under the same brand.

Figure 5. You also have to watch for battery post placement along with the various sizes.


Unless you go to a specialty battery store, most auto stores will carry only one brand of battery because there are so many alone among a single brand. They will usually be racked by warranty periods, and then possibly sub-categorized by size as well as CCA rating. Most batteries will come with warranties ranging from one to three years; however, many top of the line brands will come with up to five years or longer. The warranties only guarantee the minimum life and you can usually expect to get many more happy miles out of them, but for piece of mind of not having to go shopping again, select the battery with the highest warranty period that fits with your budget.

Figure 6. Batteries are often times sorted by warranty periods.

Figure 7. Many stores only carry one brand, but many variations.

Scheduled Maintenance

Most batteries sold now are considered maintenance-free because of the sealed cores. To extend the life of your battery, the use of a trickle charger is recommended when your Wrangler will be sitting for very long periods of time, especially in the cold. Remember, when replacing your battery, be sure to take the old one with you to turn in as you will usually get a core credit that can reduce the sticker price of the new battery replacement.

Common Questions

What are the most popular replacement batteries for my Wrangler?

You will get just as many opinions for just about each person you ask. Most common replacement batteries seem to be in the line of Red or Yellow Top Optimas, Odysseys, or Die Hard. Price ranges differ widely, so be sure to choose the correct size and CCA for your needs.

Should I consider a dual battery setup?

These systems are not cheap; however, they offer the security of always being able to start and get you to where you need to go. This is highly recommended if you have a lot of add-on electrical components, such as fog lamps, air horn, winch and travel refrigerator on board. Most folks who have a dual battery system are those who take long off-road and camping excursions. They are not necessarily recommended for the daily driver.

Related Discussions

Jeep Wrangler JK: How to Replace Starter

The starter is the only means of getting your engine up and running. A faulty starter that does not consistently crank the engine each time the key is turned can fail at any time. Replace your starter before you are left stranded with a car that won’t start.By Joseph Coelho – November 16, 2015
Contributors: John Yrigoyen.

This article applies to the JK Jeep Wrangler (2007-Present).

Starter motors and solenoids are quite robust that can generally last for years; however, it is not uncommon for them to act up or completely fail. When the key is turned to start the vehicle, power from the battery is sent to the starter solenoid, which then energizes the starter to engage the ring gear and crank the engine over. Unfortunately, starters can fail from a variety of reasons, such as cranking for prolonged periods with low battery voltage, poor electrical connections, excessive vibrations, or in the case of Jeeps that are used off-road, impact damage and water ingestion (corrosion). In many cases, vehicles that will not start are improperly diagnosed as having a bad starter. Before you decide to bite the bullet and replace the starter, check the battery and electrical connections to ensure they are not the cause of the problem. If your starter is indeed the culprit behind your starting issues, follow the replacement procedure outlined below to get your JK Jeep Wrangler up and running again.

Materials Needed

  • 10mm, 13mm, 15mm, and 16mm wrenches and sockets
  • 3/8″ drive ratchet (standard and stubby)
  • Pliers
  • Torque wrench
  • Floor jack and jack stands (optional)

Step 1 – Disconnect battery

Before attempting to remove the starter, disconnect the battery. This will prevent any wires on the starter solenoid from shorting against the engine or chassis during starter removal.

Figure 1. Disconnecting the negative battery cable.

Step 2 – Lift and support vehicle (optional)

In most cases, the Wrangler has enough ground clearance to easily slide underneath it to replace the starter. That being said, some individuals prefer a little more elbow room when working under the vehicle. If preferred, lift the car with a floor jack and support it with jack stands.

Figure 2. Lifting and supporting the vehicle.

Step 3 – Remove starter

  • The starter is located on the driver’s side of the vehicle, just above the drive line. It is often covered by a small heat shield.
  • The starter solenoid has two wires that need to be disconnected before the starter can be removed. Disconnect the electrical plug and remove the larger battery cable from its mounting stud with a 13mm socket. Take note of which stud it is on to ensure it is correctly installed during installation of the new starter.
  • Figure 4. Electrical connections at starter solenoid.
  • The starter has two bolts that secure its place, with the bottom bolt also supporting the heat shield. Begin by removing the bottom bolt with a 16mm socket. Next, while supporting the starter, remove the top bolt with a 15mm socket. With both bolts removed, the heat shield and starter can be removed.
  • Figure 6. Starter comparison.

Step 4 – Install new starter

Installation of the new starter is the reverse of the removal procedure.

  • Slide the starter into place and start both mounting bolts by hand to be sure the starter is properly aligned. Note that there are three threaded mounting holes in the starter, but only the top and bottom holes are used.
  • Slide the heat shield over the starter and proceed with tightening the mounting bolts to 25 to 28 ft/lbs. Pay close attention when tightening the bottom bolt to be sure it threads into the nut on the backside of the heat shield, as this keeps the heat shield in place. A pair of pliers or similar may be needed to keep the nut from spinning.
  • Figure 8. Mounting bolt threading into heat shield nut.
  • With the starter in place and tightened down, reconnect the electrical wiring to the solenoid.
  • Figure 9. Connecting electrical wiring to solenoid.

Step 5 – Connect battery and start vehicle

  • With the starter in place, reconnect the battery and start the vehicle to ensure proper starter operation. If the starter does not operate, check the electrical connections at the starter and battery.

Figure 10. Testing the starter by starting the car.Featured Video: 2008 Wrangler Starter Replacement

Related Discussions

Jeep Wrangler JK: How to Install Auxiliary Fuse Box

Adding a secondary fuse box to handle all your newly added accessories gives a nice clean look under the hood and is a cinch to install.By Jeffrey Smith – November 13, 2015
Contributors: BlueBruin, Zimmanski

This article applies to the Jeep Wrangler JK (2007-Present).

Adding a secondary fuse box is an excellent DIY job for someone needing to clean up their engine compartment from all the other mods they’ve installed. If you are like many other Wrangler owners, you’ve undoubtedly either dreamed of adding a fog light bar or have done it already. Throw in a CB radio, laptop port, LCD monitor, refrigerator as well as a power winch and you’ve quickly gotten yourself a rats nest of wires under the hood. With all those new goodies, you may find yourself with power surges and dead batteries. Protect your investment while at the same time cleaning up your engine compartment by installing an auxiliary fuse box. This is a very time consuming DIY job, but one that you can easily tackle if you can give yourself the time to do it. This will save you quite a bundle from taking your Jeep to a pro to have it done for you. You’ll only need a basic understanding of circuitry to do a high quality job that you’ll be proud of.

Materials Needed

  • Fuse block
  • Waterproof box for the fuse block
  • 70A circuit breaker (optional but advisable)
  • 75A relay (optional)
  • Wire cutting and splicing tools
  • Electrical tape
  • Screwdrivers

Step 1 – Assemble fuse box in the housing

It will be easier to mount the new fuse panel into the housing before mounting the unit in the engine compartment if you are planning on this type of install. Putting the fuse panel inside another box is by far the safest method to prevent dust, dirt and moisture from getting into the fuses themselves. The drawback is that a lot of bulk is added this way and finding a place to put it all can be tricky.

Figure 1. This is a waterproof fuse block rated for 100A, which will work nicely for this mod.

Figure 2. The fuse block can be mounted inside a box such as this, or you can modify something like a small tackle box for the job.

  • Figure 3. Alternatively, you can use a tackle box, fuse box and multiple relays as your secondary fuse box and block.

Step 2 – Locate spot under hood to mount assembly

Once you have found a box to mount the fuse block into, you now have the tough job of finding some place that will fit the whole thing under the hood. This can be tricky, but it can be done. If you so choose, the far right corner up by the master cylinder is a spot that this can squeeze into. There is also an existing bolt that can be removed and then re-used to mount your new fuse panel assembly. You may have to create your own bracket, or try to purchase something prefabricated that may work for your outfit.

Figure 4. This particular install used an existing frame bolt in the front corner without too much trouble.

Figure 5. Using a smaller box will open up more possibilities for other mounting locations, such as this one above the battery.

Step 3 – Add extra protection to your new fuse panel

This is a completely optional step, but the inexpensive cost, few minutes that it takes to add a breaker and a relay to the fuse assembly is a great bit of insurance as well as piece of mind to keep you on the road. On the outside left side of the fuse box is enough area and space to add the optional 70A circuit breaker and 74A relay. The breaker will prevent anything from frying your new fuse panel and the relay will help divvy and control the power draw on the new fuses.

Figure 6. Both the relay and the breaker will fit perfectly on the side of your fuse box.

Step 4 – Run #8AWG wire from block

Drill a hole on the front end of the fuse box to allow pass through of the thick wire from the fuse block outside of the box and to the circuit breaker. You’ll run another section of this wire from the breaker to the relay. This is going to protect not only the fuses and block, but the smaller gauge wire that runs from your accessory plugs.

Figure 7. Drill a port hole on the side of the fuse box, then run the #8AWG wire from the block to the breaker and to the relay.

Step 5 – Make connections from accessory port to relay

You’ll need to open up your dashboard to get access to the accessory port, or cigarette lighter. You will be tapping into the power supply from the lighter and splice in new wire to run to the relay through the firewall. You will want to run at least a 14 gauge wire as your spliced wire and run it back through the dash into your fuse box to finish the connection at the relay.

Figure 8. You’ll need to open your dash to get access to your accessory plug.

Figure 9. This is the power supply to the cigarette lighter, which you will splice into.

Step 6 – Run final power from battery to fuse box

Use the heavy gauge wire from your battery to the fuse block to power it up. Once all the connections have been terminated, reset the circuit breaker and put the key in the ignition. Use a voltmeter to test the power into the fuse box and each fuse on the block to make sure everything is within the proper range. If it reads good, put the dash back in order and start your Jeep. Make sure no electrical P-codes are present and no other CEL are illuminated. Take her for a test drive. If there are no problems, load your new equipment one by one, so if there’s a blown fuse, you can easily identify what caused it and make the necessary corrections.

Figure 10. Make the final power run and check the voltage levels with a voltmeter at the new fuse block.

Featured Video: DIY Relay and Fuse Box

Related Discussions

Jeep Wrangler JK: How to Use SeaFoam

Of all the magic additives out there, SeaFoam has a lot of believers. It is cheap as well as easy to use, and just may be worth a try.By Mark Garrett – November 16, 2015

This article applies to the Jeep Wrangler JK (2007-Present).

SeaFoam appears to actually work in both cleaning the crankcase and fuel system. Modern oils should do an excellent job of keeping your crankcase clean, but if you have a used vehicle, it may take care of past sins. Keeping your crankcase extra clean is not a bad idea. Modern fuels are the same, but fuel injectors really need to be clean to perform correctly, so a cleaner for the fuel system is actually a good idea. SeaFoam may be the solution for your idling or performance issue, so let’s give it a try.

Materials Needed

  • Plastic funnel for gas tank
  • Small plastic funnel
  • SeaFoam

Step 1 – Add to fuel tank

SeaFoam suggests using one can of treatment for up to 16 gallons of fuel.

Figure 1. SeaFoam cleaner.

The more you use, the better it works; for instance, you can add one can to eight gallons of fuel. If you are also adding it to your engine, it is fine to add 1/2 can to the tank and 1/2 can to the engine. Remove the gas cap and pour the SeaFoam into the tank using a funnel. After adding it to your gas tank, just drive as usual to let the SeaFoam circulate throughout the fuel system.

Figure 2. Add to fuel tank.

Pro Tip

The general consensus is adding a can to your tank every oil change works well.

Step 2 – Add to intake

If you are having knocking issues or the engine is running rough, the quickest results happen if you add the SeaFoam through a vacuum line on the engine. Though it is quicker, you have to use caution since you are adding a liquid to the combustion chamber that is made to handle vapor. Most Jeep people add the SeaFoam through the vacuum brake booster hose.

Figure 3. Booster vacuum hose.

Remove the end of the hose shown in Figure 3. Start the engine and allow to run. It may idle rough since the vacuum hose is disconnected. Using a small funnel, slowly poor the SeaFoam in the hose. The engine will probably run rough and may make some noise, but continue to pour 1/3 of the can in. Shut the engine off for 30 minutes or so. Now start your engine and allow to idle. It will smoke like crazy since all of the stuff is burning out of the engine. You can rev it up after a bit and let the smoke die down.

Figure 4. Smoke from exhaust after restarting.

It is fine to drive your Jeep now and continue to let the stuff from your engine get cleaned out. A lot of people say their Jeep runs better and smoother after treatment.

Pro Tip

Don’t be tempted to stick the hose into the can, since taking a slug of liquid could hydro lock the engine.

Step 3 – Add to engine oil

SeaFoam will clean out your crankcase whether there is a little buildup or a lot. SeaFoam suggests using one to 1-1/2 ounces of additive to one quart of oil. One can should be just about right for your Jeep. Pour it into the oil filler cap and replace it.

Figure 5. Add SeaFoam to engine oil filler.

After putting SeaFoam into the engine oil, most people feel that the oil should be changed after a few hundred miles. The oil should look more dirty than usual after and deposits are washed out by the additive.

Pro Tip

Some fellow Jeep enthusiasts say that Mopar Combustion Chamber Cleaner, Chevron Techron, Marvel Mystery Oil and other additives work just as well. Personally, SeaFoam is the only cleaner that I have seen work, but the other may work well.

Related Discussions

Jeep Wrangler JK: How to Clean Throttle Body

A dirty throttle body will cause a delayed throttle response, hard pedal feel, and a rough idle. This article will assist you in cleaning the throttle body in the Jeep Wrangler.By Bassem Girgis – November 16, 2015

This article applies to the Jeep Wrangler JK (2007-Present).

The throttle body in your Jeep Wrangler controls the air to fuel mixture. The dirtier it gets, the more constricting it becomes. A dirty throttle body will affect your throttle response. You can also diagnose a dirty throttle body by how rough your Jeep is idling, again, because of how constricting the dirt and debris is. Cleaning it solves all of these problems almost immediately. You will need to remove a few components to clean it, but the results are well worth the time you will invest in it. Read on to learn how you can clean your Jeep Wrangler’s throttle body.

Figure 1. Throttle body.

Materials Needed

  • Wrench
  • Torx screwdriver
  • Flat head screwdriver
  • Throttle body cleaner

Step 1 – Disconnect battery

Disconnect the negative (black) battery cable. Simply use your wrench to loosen the nut, then pull it up and wrap it in a towel to avoid any contact with metal.

Figure 2. Disconnect negative battery terminal.

Step 2 – Remove intake tube

To reveal the throttle body, you will need to remove the intake tube attached to it. First, remove the temperature sensor by sliding the red tab back, and then pulling it out. Then, use your screwdriver to loosen the screw on the clamp around the intake tube attaching it to the throttle body and remove the intake tube. You can either push it aside now, or you can loosen the screw on the other side by the air box and remove the tube completely out of the way.

Figure 3. Disconnect temp sensor.

Figure 4. Remove intake tube.

Step 3 – Remove throttle body

Remove the four Torx screws holding the throttle body in place, and then pull the throttle body out.

Figure 5. Remove throttle body.

Step 4 – Clean throttle body

Use throttle body cleaner (or Sea Foam) to spray the assembly, then watch all the dirt and debris slide off. Spray it and wipe it as needed until you feel it looks clean.

Figure 6. Dirty throttle body.

Figure 7. Clean throttle body.

Step 5 – Install throttle body

Installation is the reversal of removal.

Simply align the throttle body in place, then tighten the four Torx screws to hold it in place. Attach the intake tube to the throttle body and the air box, tightening both clamps’ screws. Connect the temp sensor and connect the negative battery cable.

Figure 8. Throttle body installed.

Related Discussion

Jeep Wrangler JK: How to Check Engine Codes

The Jeep Wrangler is equipped with a computer designed to point out the faulty components. This guide will help you understand how to check for engine codes.By Bassem Girgis – November 16, 2015

This article applies to the Jeep Wrangler JK (2007-Present).

Your Jeep Wrangler has tons of components that play a role in making it the car that you drive today. Almost all of the little components are wires to sensors, so when they go bad, it notifies your Jeep’s computer and the computer notifies you with a code. The folks that designed the Jeep made it even easier; now you can check for engine codes without even using an OBD-II scanner. This articles will go over the sequence to get your car to tell you what’s wrong with it. Read on to learn how to check for engine codes in the Jeep Wrangler.

Figure 1. Engine code on instrumental panel.

Materials Needed

  • No tools needed

Step 1 – Understand how to read codes

The engine codes are made out of five digits.

The first digit is a letter. You may have one of four letter: B (body), C (chassis), P (powertrain), or U (network).

The second digit will be either a 0 (SAE) or a 1 (MFG).

The third digit indicates one of eight things: 1 (fuel and air metering), 2 (fuel and air metering injector circuit), 3 (injection systems or misfire), 4 (auxiliary emissions control), 5 (vehicle speed control and idle control system), 7 and 8 (transmission).

The last two digits indicates the faults, which can go from 00 to 99.

Step 2 – Turn key to ON position

Insert your key into the ignition and turn it to the ON position, but don’t start the car. Push the key into the ignition and turn it to the OFF position, while holding it in. Then turn it back to the ON position. Repeat this process three times in a row and stop on the ON position on the third time.

Figure 2. Turn the ignition from ON to OFF three times, while pressing it inside.

Step 3 – Read the code

When and if you do Step 2 successfully, the dash light will turn on and off, then a code will appear. Take a note of that code. However, if you get a massage that says “done,” it means you have no codes to read. If nothing happens after Step 2, repeat it and be sure you are not waiting too long between turning the ignition on and off.

Figure 3. Engine code.

Pro Tip

To check the code, visit Wayalife or Quadratec sites. They offer a full list of codes for the Jeep Wrangler.

Related Discussions

Jeep Wrangler JK: How to Reset Your ECU

If you have just installed some performance mods but your Jeep hasn’t responded yet, you may need to reset your ECU.By Jeffrey Smith – November 13, 2015

This article applies to the Jeep Wrangler JK (2007-Present).

So you have spent a small fortune on various performance modifications, but haven’t seen the results of your efforts yet? It is likely that your engine’s computer hasn’t yet adjusted to the new parts and is still trying to run with the existing OEM settings. This can be frustrating and really annoying. There is a simple fix for this. Your engine’s settings for such things as fuel to air ratios are automatically set at the factory for optimum stock performance. When you add new enhancements to such systems, the computer needs to make adjustments as well, and it sometimes needs a kick in the pants to get it in gear. Fortunately for you, this is a simple, no-special-tools-required procedure that will only take a matter of minutes to perform. Once you have performed this procedure, your Jeep may take up to about 50 warm-up periods (give or take) for the computer to learn the new optimum settings. The results of all your hard work should soon come to fruition.

Materials Needed

  • 8mm wrench to remove battery cables
  • Key

Step 1 – Remove the positive (red) battery cable

Use your wrench or ratchet to remove the positive battery cable. Only remove the positive cable. Leave the negative cable in tact.

Figure 1. Remove the positive (red) battery terminal only.

Step 2 – Ground the red cable to the negative terminal

Ground the positive battery cable to the negative battery terminal for about 30 seconds. Alternatively, you could also first disconnect the negative cable and move it well out of the way, then disconnect the positive cable and ground it to the metal frame for about 30 seconds as well. Either method should work.

Figure 2. Either ground the red to the black, or disconnect both and ground the red to a metal part of the frame.

Step 3 – Reconnect the positive battery cable

If you only disconnected the red cable and ground it to the black, reconnect the red cable now. If you used the alternative method, reconnect the positive first before reconnecting the negative cable.

Figure 3. Regardless of which method you use, always connect the positive cable first.

Step 4 – Turn on your Jeep

  • Insert your key into the ignition.
  • Turn the key to the “ON” position.
  • Do NOT start the engine.

Figure 4. Insert the key and turn it to the “ON” position only. Do not start your Jeep.

Step 5 – Cycle the headlights

With the key in the “ON” position, turn your headlights on and then off again.

Figure 5. Turn your headlights on and then off.

Step 6 – Turn the key off and remove

After you have cycled your headlights, turn the key off. The ECU has now been factory reset. It will take approximately 50 warm-up periods or driving cycles to re-learn the new optimal engine performance settings, and you should see all the modifications that you have made in full swing.

Figure 6. It will take up to 50 driving periods for the ECU to figure out the new performance settings.

Related Discussion

Jeep Wrangler JK: How to Replace Air Filter

The Wrangler’s air filter is easy to access. It’s right up in front under the hood, and you can change the filter–even on a rocky trail–in 15 minutes.By Scott Phillips – November 13, 2015
Contributors: 2CarPros 

This article applies to the Jeep Wrangler JK (2007-Present).

Your Jeep 3.8 EGH or 3.6 Pentastar engine is an efficient and powerful air pump. It draws air from under the upper-right front of the hood, mixes that air with gasoline and compresses as well as burns the volatile mixture. The vigorous combustion force drives the wheels and the hot, spent mixture is cleaned of contaminants and pumped out the exhaust. To protect the engine, the outside air is filtered. But when the filter begins to clog, it chokes off some of the incoming air; the combustion force is reduced and your Jeep loses power.

The Jeep’s maintenance manual prescribes changing the filter every 30,000 miles, but dusty off-roading can clog the filter very quickly. The OEM Jeep filter is part number 68257791AA, and every auto parts store has several filter choices as well. Aftermarket filters may be made of disposable paper for economical single-use, or long-lasting, washable fabric. However, most Wrangler owners have found that the oiled, reusable filters clog very quickly in dust and dirt; and should be avoided for off-roading. Fortunately, there are several non-oiled “dryflow” filters on the aftermarket, which are of good quality and washable. In either case, look for a filter with a rubber lip to seal the air box tightly and keep out destructive dirt.

Figure 1. Engine air filters.

Materials Needed

  • Engine air filter
  • 10mm socket wrench
  • Mechanic’s gloves
  • Shop vac (optional)
  • Flashlight

Step 1 – Open the engine air filter box

Caution: Do this work after the engine has cooled.

  • Reach down around the four corners of the air box and unsnap the four clips that hold the top of the box on. Push the clips outwards at the top. See Figure 2 below for a close-up view of the clips.
  • Use the 10mm wrench to remove the two bolts that fasten the air intake snorkle to the radiator shroud. This is to allow the air box lid greater movement.

Figure 2. Engine air filter box.

Pro Tip

Wear mechanic’s gloves to protect your hands from rough or sharp edges.

Step 2 – Remove and replace the air filter

  • Lift the air box lid and tilt it upward by flexing the intake snorkle.
  • Lift out the old air filter.
  • Vacuum the dirt out of the bottom of the air box, if needed.
  • Install the new air filter with the pleats facing down and the tapered end inboard.
  • If the old filter appears fairly clean, perform the flashlight test in Step 3.

Figure 3. Remove and replace air filter.

Step 3 – Air filter contamination flashlight test (optional)

Hold a bright LED flashlight under the new air filter and note how much light passes. Then do the same with the old filter and see how it restricts light passage. The light restriction is a fair comparison to the airflow it restricts and helps in judging how contaminated the filter is. In the picture below, see the comparison between the new filter and the very dirty filter. Note how the dirt and oil vapor change the bright blue-white LED to dim green.

Figure 4. Air filter contamination flashlight test.

Step 4 – Close the engine air filter box

  • Snug the air box lid down around the lip of the new air filter and ensure that it is seated.
  • Close the four clips on the corners of the air box.
  • Install the two bolts that fasten the intake snorkel to the radiator shroud.
  • Using the 10mm wrench, check the tightness of the intake snorkle clamps.

Figure 5. Close engine air filter box.

Pro Tip

Tug lightly on the air box lid to test it for security and ensure that the four clips remain tight.

Step 5 – Air leak and MIL fault check

Start the engine and let it idle. Ensure the multi-function indicator lamp (MIL) is out. Then listen near the air box and intake duct for the whistle or hiss of an air leak. If you hear an air leak, recheck the seating of the filter’s rubber bead in the air box and that the lid is on tight. Also, insure that the intake clamps are tight.

Pro Tip

An air leak may light the MIL. Once you fix the leak, the MIL can be cleared.

Featured Video: Air Filter Replacement

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