GM PCM Reset. And 5 Reasons Why You Shouldn’t Do This

There are many benefits to resetting the powertrain control module (PCM) of a GM vehicle. Chief among these is that the process helps in removing errors or glitches that are randomly happening in the system of your auto. It also brings back the stock configurations of your car to optimize performance and fuel economy as its manufacturer originally intended.

PCM problems highlights

• Module's importance:Extremely high
• Prone to failure:Yes
• Reasons for failure:Water, damage, ECM problems, TCM problems
• Ways to reset:Disconnecting, scanner tool diagnostics
• Sphere of control:Powertrain (engine, transmission, AWD systems)
• Symptoms of failing:Powertrain anomalies, powertrain codes
• Price to repair:$180 - $300
• Price to replace:$750 - $1,650

When to Reset the PCM

Resetting the PCM can be a good way to solve a problem for a number of reasons. This can be particularly useful in the following conditions:

• First, if the software of the PCM has become corrupted, resetting it can often restore its proper function.
• Second, if you have replaced a part and the PCM refuses to play along with it, resetting it will help the proper integration of the new component.
• Third, if the vehicle has been modified (for example, with a new chip or other aftermarket modification), resetting the PCM can often help return the vehicle to its original state.
• Finally, if the vehicle is having trouble starting or running properly, resetting the PCM can sometimes correct the issue. If you're experiencing any of these problems, resetting your PCM may be a good solution.

Ways to Reset the PCM of a GM Vehicle

Your car's PCM is a computer that controls the engine. So, if you are experiencing problems with your engine, you may need to reset the PCM so it will bring it back to its ideal configuration.

There are a few ways to reset your PCM, and these include:

1. Resetting the PCM Thru an OBDII Scanner

An OBDII scanner is a diagnostic tool used to reset some errors and check engine light codes. OBDII scanners connect to your car's computer and can read (and sometimes clear) the error codes that are causing warning lights or fault codes to come on. This can save you a lot of time and money by helping you diagnose the problem yourself, or at least narrow it down for your mechanic.

The steps to reset your PCM using a scan tool varies depending on the make, model, and interface of your OBDII scanner.

Generally, it can be as simple as the following:

• Make sure that the ignition is off.
• Open the driver's door and locate the OBDII connector beneath the dashboard. It's typically near where your left foot would be if you were driving.
• Plug in the scanner and turn on the ignition switch. The scanner will then initialize and communicate with the PCM.
• In the options, choose the appropriate command to reset the fault codes in your car.
• Follow the prompts on the scanner to complete the reset process.
• Start the engine and test drive the vehicle to see if the problem has been resolved.

2. Resetting the Battery

This method usually works for resetting the ECU of vehicles manufactured before 2005, but it may not work for newer vehicles with more advanced memory modules. Nonetheless, it's worth a shot.

This involves the following steps:

• Begin by unplugging your battery's cables. Remember to remove the negative (-) cable first, as starting with the positive (+) cable can cause battery arcing, which can damage your car.
• Maintain this state for at least 15 minutes but no more than 30 minutes. You can also use a jumper cable to connect the negative and positive cables for two minutes to completely drain the excess current and effectively reset the system.
• Next, turn on the ignition but do not let the engine run. This should turn on all of the dashboard lights.
• Lastly, turn your car off again, and this time start your engine normally, idling for 15 minutes. If done correctly, your ECU will recalibrate after at least a hundred miles and any errors in your dash will be removed.

Reasons Why Resetting the PCM is Not Recommended in Solving Problems

There are a few reasons why you might want to reset your PCM. Maybe you're troubleshooting an engine problem, or maybe you just replaced the battery and now all sorts of warning lights are lit up on your dash. In any case, it's important to know that resetting your PCM can have some serious consequences, and should only be done as a temporary or last resort.

Here are just some of the many reasons why this solution may not be the best course of action for a given problem:

1. You Lose Crucial Information About a Problem

Your car computer controls all its electronic parts and their respective functions. These include the components responsible for monitoring or managing its mechanical workings.

If a fault is present, the computer will display the code via the OBD2 scanning tool, and depending on the fault, the computer will attempt to adjust the system to allow the vehicle to be driven. So, if the codes are not deleted after the fault has been repaired, the code is still stored in the OBD2. That's because the computer will believe there is still a fault and will continue to display a warning for it.

Likewise, the processes listed here will work if the things troubling your dashboard are simply a result of a system glitch or software-induced problem. However, these should not serve as an alternative fix to faulty or malfunctioning hardware in your car.

If you do reset the PCM before the real problem coming from a faulty part is fixed, it will just complicate matters for you. Erasing codes does more than simply disable the malfunction indicator lamp (MIL) in your vehicle. Since those lights don't illuminate for no reason, and the system is intended to aid in the diagnosis of several problems by providing failure records, resetting the codes also erases the data that caused the light to appear in the first place. This means that you've made the job of locating the source and nature of the problem more difficult, and thus, more expensive for yourself.

For short, by erasing the failure records, you just lost the opportunity which would have made the diagnosis much easier by providing the data critical to resolving the issue.

2. You May Experience Drivability Issues

After resetting the PCM, there is a chance that your car may experience drivability issues. These usually manifest as stalling, hesitations upon acceleration, and random misfires. If you encounter these problems after you've reset the computer, the first thing you should do is to take it back to the shop or dealership and have it scanned for any codes that may have been stored in its memory.

If no codes are found and the problem persists, then it's most likely that the issue isn't with the PCM but with another part of the vehicle. In this case, simply reverting the changes made by the reset will not fix things. In fact, it may even make them worse.

3. You Might Void Your Warranty

In some cases, resetting the PCM might void the warranty of your vehicle. This is because most dealerships and manufacturers consider this kind of action as tampering with the original settings of the computer. If something goes wrong after you've reset the PCM and you still have an active warranty, they may not shoulder the repairs needed to fix the problem.

4. Cleaning is Sometimes a Better Solution

If you're experiencing idling issues or poor drivability, it's likely that there's carbon build-up in your engine or other vital parts of your vehicle. Simply resetting the PCM will not get the contaminated components cleaned or fixed.

One example is if your throttle body is already dirty and in need of cleaning, simply resetting the PCM will not address the real problem. The best way to go about this is to have the throttle body cleaned first before considering a reset if the same error still points to a problem that has already been repaired.

5. It Comes with Some Risks

You can reset the PCM on your own, but you should only do so if you're confident in your skills and knowledge. If you're not sure about what you're doing, it's always best to leave the job to professionals.

Working on your car's computer also comes with certain risks. For one, you might accidentally damage other parts of the vehicle while trying to access the PCM. Second, there's also the possibility of causing more problems than there were in the first place if you mess up the timing of some of your vehicle's important components.

Unless you know exactly what you're doing, it's best to leave the job to those who are trained and experienced in working on cars.

Conclusion

Resetting the PCM can offer some benefits, but it also comes with certain risks. Weigh the pros and cons carefully before deciding whether or not to proceed with the reset. And when in doubt, always consult a professional.