8 Most Common Jeep Cherokee PCM Problems

The Powertrain Control Module (PCM) is a computer that controls your vehicle’s essential functions, such as changing gears and anti-lock brakes. It monitors the air-to-gas ratio, performance, and ignition timing. By controlling both the transmission and engine, the PCM can easily coordinate functionality and improve the vehicle’s performance.

Sometimes, however, the PCM runs into problems. With the Jeep Cherokee in particular, owners have come across issues they’ve encountered with it.

Here are some common Jeep Cherokee PCM problems:

  1. It shows random error codes.
  2. The engine stalls or misfires.
  3. The check engine light comes on.
  4. The vehicle has difficulty starting.
  5. The engine has performance issues.
  6. There is damage to the circuit board.
  7. There are transmission issues.
  8. Problems with sensors become more noticeable.

A PCM can fail due to several factors, such as a short circuit, corrosion, or thermal stress. Problems may also occur if vibration causes micro-cracks in the unit. Determining why the PCM specifically fails is essential in avoiding the same damage to the replacement. Additionally, it will prevent costly repairs and misdiagnosis of your Jeep’s issues.

8 Jeep Cherokee PCM Problems

White 2019 Jeep Cherokee

1. It shows random error codes.

The PCM may display random error codes (also known as OBDII codes), even if nothing is wrong with your Jeep. There are a total of 5000 generic and manufacturer-exclusive OBDII codes programmed into Jeep vehicles. But you would know that you are having Jeep Cherokee PCM problems if your code scanner is reading random codes that begin with a “P06.” Click here for a full list of powertrain error codes.

2. Engine stalls or misfires.

One function of the Jeep Cherokee PCM is to control fuel injection and determine the right time to switch gears. If the PCM is faulty, it can lead to stalls or rough idling. Unfortunately, this is part of the 1998 Jeep Grand Cherokee PCM problems, and one of the most frustrating issues owners had to address.

3. The Check Engine light is on.

The PCM may provide wrong inputs, which leads to other problems. Among these are engine light issues and power steering, according to Jeep Cherokee owners. The Check Engine light turning on randomly tops the list. Reasons that your Check Engine light turning on include emissions problems, faulty O2 sensors, and problems with the PCM. A mechanic with the right tools can analyze your vehicle’s error codes and let you know the problem or if your PCM is at fault.

If you end up replacing your PCM and the Check Engine light comes back on after, don’t immediately assume that the replacement PCM is faulty. Something else is wrong with the vehicle that needs to be located, diagnosed, and repaired.

4. Jeep Cherokee has difficulty starting.

Like the Check Engine light issue, this part of the 1994 Jeep Grand Cherokee PCM problems stems from a faulty PCM providing wrong input to the vehicle. When this happens, ignition or starting issues occur. If your PCM is defective to a point where it cannot make adjustments to the timing or air-to-fuel ratio, then your Jeep may not even start. Don’t confuse this with a bad starter or a blown alternator. It is best to check these parts and see if they need replacement. If you’ve already done so and are still having difficulty with starting your Jeep, then your PCM is most likely to blame.

5. The engine has performance issues.

Since the PCM controls your air-to-fuel ratio and transmission, a faulty unit may decrease your fuel efficiency, power, and acceleration. Your fuel mileage may inexplicably worsen. A defective PCM can also make your vehicle sluggish and troublesome when suddenly accelerating or driving uphill. Other performance issues include your Jeep running poorly and having a wide variety of electrical problems.

6. There is damage to the circuit board.

Corrosion, shorts, and loose connections can contribute to PCM issues, especially to 2000 Jeep Grand Cherokee PCM problems. Owners reported this specific problem with the electrical system. You need to perform a soldering repair to fix these bad connections. It requires considerable skill, as PCMs for Jeep Grand Cherokees have poor soldering on the 5-volt power connection.

7. Transmission issues surface.

Take note that this applies to automatic-transmission vehicles only, as the PCM has no control over the transmission of a five-speed stick shift. You will notice that your Jeep shifts erratically or seemingly at random. If you have done numerous repairs on the automatic transmission on your Cherokee and replaced your automatic transmission fluid but are still having problems, then you have a faulty PCM.

8. Issues with sensors become more noticeable.

Your PCM has sensors on the radiator, the air filter, the vacuum pipe, the throttle body, and the crankshaft, to name a few. These sensors shouldn’t cause any disasters, but they can cause your PCM to make unnecessary adjustments that will affect your Jeep’s performance. Sensor issues rarely point to a defective PCM – usually, faulty sensors need replacement to resolve the issue.

Voltage vs. Damage

In diagnosing a faulty PCM, the presence of powertrain error codes does not automatically pinpoint a problem with the unit itself. It may be with the wiring harness, the power delivery, or physical damage to the unit. Causes for PCM failure typically fall under either incorrect voltage or environmental factors.

Incorrect Voltage

Incorrect voltage can go both ways – either it’s too high (overload), or it’s too low. Here’s how each leads to PCM failure.

Voltage overloads are due to a short in a solenoid or actuator circuit of the PCM, or if your Jeep is somehow shocked or experiences power surges. This excessive electricity fries your PCM, rendering it unable to recover from the jolt. A Jeep Cherokee PCM replacement will be pointless if the shorted solenoid or actuator is not located and fixed, as the voltage overload it creates is guaranteed to damage the replacement unit. Similarly, if the transmission or fuel injector wires become corroded, they can lose conductivity and lead to engine failure.

If you suspect the wiring harness, perform a visual inspection and replace any frayed wires or corroded contacts. If everything looks good visually, follow up with a multimeter to make sure you do not miss anything. A new starter can also cause your PCM to fail, so ensure that it does not lead to a power surge when starting your Jeep as installing one frequently bypasses the surge protector on your PCM.

Low voltage is another cause of a faulty PCM. It occurs when the battery ground has shorted out to the vehicle’s frame, or if you have a failing battery or a weak alternator. While most of your vehicle’s systems can run on less than 12V, dead battery cells can impact your PCM long before you notice issues with your starter or headlights. Replacing your battery will typically fix the problem.

Red Jeep Cherokee in the Rain

Environmental Factors

Water is your PCM’s Public Enemy No. 1. If water gets inside the unit, it can short circuits and ruin electronic connections permanently. Mud is no exception. Expectedly, a Jeep Cherokee PCM repair would be impossible as sudden PCM failures due to submerging your Jeep in water or mud would usually warrant a PCM replacement. So when going off-roading, exercise moderation and remember that your Jeep Cherokee cannot swim.

Likewise, corrosion, thermal stress, and vibration adversely affect the proper function of your PCM. An example of this would be the sensors in your PCM. Magnets, moving parts, and sensitive measuring elements subject to vibration and wear more than the computer’s solid-state components comprise these sensors. So if you frequently ride on rough terrain, chances are you will get more sensor issues than those who use their Cherokee as daily drivers.

If neither of these reasons is the cause behind your faulty PCM, then chances are the error codes your OBDII scanner (view on Amazon) gives is on point. If so, perform diagnostic procedures based on the exact error code you’re reading. Following the recommended troubleshooting steps typically gets the problem fixed.

Resetting the PCM on a Jeep Cherokee

If you encounter any of these problems, have checked on the other components of your vehicle, and have identified that your PCM is neither toasted nor physically damaged, then resetting your PCM may be the only thing needed. Here are steps on how to reset your Jeep Cherokee PCM:

  1. Disconnect the positive battery terminal and touch it to the ground for 30 seconds to discharge the PCM capacitors, maintaining the PCM’s adaptive memory. 
  2. Reconnect the battery cable.
  3. Turn the ignition switch “On” but don’t start the engine.
  4. Turn the headlight on.
  5. Turn the headlights off.
  6. Turn the ignition key off.

Voila! Your PCM is successfully reset!

Some Jeep Cherokee owners follow a completely different set of steps, namely: disconnecting the battery overnight (for at least eight hours), reconnecting it in the morning, starting the engine up, and letting it idle until it has heat cycled a couple of times (meaning the thermostat has opened and closed). They would then drive their Jeep Cherokee normally around town for a while before taking it out on the highway. This process works better for them and allows their Jeeps ample time to relearn their driving habits or pattern. The vehicle’s adaptive learning phase takes many miles of driving and quite a few fresh starts.

A word to the wise – it is a good idea to reset the PCM every other year or whenever you regear, replace your Jeep’s O2 or TPS sensors, or change the level of fuel Octane you use.

Jeep Cherokee PCM Replacement

If resetting does not work, then you may need a Jeep Grand Cherokee PCM replacement. So how do you do it?

First, get the correct replacement PCM specific to the make and model of your vehicle. You cannot just get any model year Grand Cherokee PCM – it has to be an exact match to your car. The replacement unit is plug-and-play, so installation is easy and is essentially a matter of swapping boxes.

Next, determine the PCM location inside the instrument panel, climate control system, or under a seat. For instance, to resolve 2004 Jeep Grand Cherokee PCM problems, you will need to access the cowl panel in the engine compartment’s right or rear side.

Then, disconnect the battery before removing the old PCM and installing the replacement unit. This step is one thing most installers forget to do. After this, you can reconnect the battery.

Lastly, allow the replacement PCM to undergo its relearning phase. This phase may require you to take the vehicle for a short drive cycle (going over 35 mph), so the computer can adjust itself and run properly. Note that most PCMs continue to learn and adapt over time to your Jeep’s different functions as it stacks miles. It may take some time to relearn your driving habits, too, so you may experience rough or awkward shifting until this occurs.

A PCM replacement is best done by your dealer or a service station since it requires reprogramming to match your Cherokee’s VIN. A replacement unit is also quite expensive – up to $900 for new and below $500 for refurbished or remanufactured ones (not including tax and labor) – and should only be done if you tried all other options to fix your PCM. Also, avoid purchasing remanufactured PCMs online as these are proven to fail after only a year of installation. Go for high-quality refurbished PCMs with a lifetime warranty.

Frequently Asked Questions

How do you know if a PCM relay is bad?
These three symptoms indicate a bad PCM-relay: 

  • You get no power when you insert the key.
  • The engine will not start.
  • You experience a massive battery drain or a dead battery.

Is a Jeep Cherokee PCM interchangeable?
If it’s the same engine year, the same type of transmission (automatic), and the ECM numbers and factory alarm match, then your replacement unit should work. Be extra careful when securing replacements for year models older than 1997, as FCA made changes to the PCM configuration for ’98 models and above.

How do you repair a Jeep Cherokee PCM?
Before you begin the repair, you’ll need a 60/40 rosin core (not acid core) solder and a non-corrosive contact cleaner. Then you remove the PCM covers, clean off any potting compound from the electrical connector that is soldered on, reflow the solder from each pad to its connector with as little an amount as possible. Ensure not to touch any other connectors or copper circuits as any damage will permanently destroy your PCM. You may also clean all contact with contact cleaner before reassembling your PCM.

This video by Ozzy’s Auto Repair shows how to do a PCM repair for a Jeep Grand Cherokee properly:

Is there any Jeep PCM recalls?
FCA released a recall order for some 2014-2018 Dodge Durango and Jeep Grand Cherokee vehicles equipped with a gasoline-fed engine and Cruise Control. It was due to the PCM locking the Cruise Control’s positive torque request. So unless the driver shifts to neutral or applies brakes, the vehicle either maintains or accelerates its current speed, resulting in a possible unforeseen vehicular crash. The firm also recalled 86,000 units of its 2019 year model due to transmission issues during deceleration. For both recalls, FCA advised affected Cherokee owners to have their Jeep dealer inspect the software level of their PCM and reprogram it as needed to fix the problem.

Conclusion – Jeep Cherokee PCM Problems

In summary, here are the most common Jeep Cherokee PCM problems:

  1. It shows random error codes.
  2. The engine stalls or misfires.
  3. The check engine light comes on.
  4. The vehicle has difficulty starting.
  5. The engine has performance issues.
  6. There is damage to the circuit board.
  7. There are transmission issues.
  8. Problems with sensors become more noticeable.

If you are experiencing these issues, have your codes read first to avoid a cheap repair option that won’t last long. Isolate which of the computer’s requirements are out of place – be it sensor inputs, proper battery voltage, or good ground. Covering these will help determine the need for a fix or replacement, or if other components have to be repaired for the PCM to function properly.

Kris Peter

Adventure seeker and off-road enthusiast. I love the thrill of going off-road and taking on the elements.

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