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Summary
  • The powertrain control module (PCM) controls the powertrain. Some of the parameters it monitors include engine speed, coolant temperature, and throttle position.
  • The PCM uses data from the different sensors to ensure optimal operation. For example, it uses data from oxygen sensors to determine how much fuel the engine needs.
  • Software issues, electrical issues, power surges, charging system problems, moisture, and extreme temperatures can affect the PCM.

Modern vehicles are complex, consisting of several systems that work together to ensure their smooth performance. They rely on computers like the PCM or powertrain control module to stay on top of their functions.

What Is a PCM?

The PCM  It is responsible for controlling the powertrain, which includes the engine and transmission. It monitors parameters, such as engine speed, coolant temperature, and throttle position. The device also controls outputs, such as the fuel injectors and ignition coils.

It is known as the engine control module (ECM), digital motor electronics (DME), and transmission control module (TCM) in some vehicles. Generally, an ECM is a PCM if it controls and oversees both the engine and the transmission operations.

How Does a PCM Work?

The PCM receives data in the form of signals from the sensors and components connected to it and makes decisions based on them.

Some examples of the decisions it makes include how much fuel to inject into each cylinder, when to fire the spark plugs, and when to make the transmission shift to a different gear to deliver the best performance relative to its current condition.

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Cutout of a Car ECU or PCM
Cutout of a Car ECU or PCM

When the flow of information between the PCM and other onboard computers and sensors is undisrupted, the vehicle performs smoothly and efficiently.

However, if something in the system fails, the PCM won’t know what to do. For example, if an oxygen sensor becomes faulty, the PCM won’t know how to adjust the air-fuel mixture going into the engine. The check engine light can turn on and the engine might run roughly or have acceleration issues.

If the PCM itself fails, the engine might not start at all.

What Causes PCM Failure?

PCMs are generally built to last longer than any of a car’s sensors. More often than not, software concerns—not internal hardware problems—cause PCM issues.

Other common causes of PCM failure include an overload from a shorted component or circuit, power surges, charging system problems, and environmental issues, such as moisture and extreme temperatures.

What Are the Symptoms of a Bad PCM?

Because the PCM is responsible for a wide range of vehicle operations, it can cause many problems when it fails. Here are some of the most common telltale signs of a bad PCM.

For a more comprehensive discussion on the different symptoms of a bad PCM and what it means for your vehicle, check out this article.

Can You Drive a Car with a Bad PCM?

Whether you can drive your car with PCM issues or not depends on the problem itself.

For example, if the internal power supply fails, the fuel injectors won’t turn on, so the engine won’t receive any fuel. When that happens, your vehicle won’t run at all.

If the issue is less severe, it is possible to drive your car with a bad PCM. However, keep in mind that the PCM can develop issues that can compromise your safety on the road without any warning.

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So it would be best to stop driving your vehicle until you can have its bad PCM repaired or replaced.

How Much Does a PCM Repair Cost?

If your PCM only needs to be reprogrammed for it to work properly again, you can expect to spend anywhere between $80 and $150 to repair it. The PCM reprogramming might remove errors or bugs in the software and restore the computer’s great performance. However, if the PCM itself is damaged, you’ll need to replace it entirely.

How Much Does It Cost to Replace a PCM?

An aftermarket PCM replacement can cost you anywhere from $50 to $1000 on parts alone. Its price depends on various factors, like the part’s brand, condition, quantity, and your vehicle’s specifications.

car engine control module with white background
An aftermarket PCM replacement can cost you anywhere from $50 to $1000 on parts alone.

As for labor, you can expect to pay around an extra $100 to $300 to have your damaged PCM professionally replaced. Of course, this is only an estimate and might vary depending on your vehicle and the rates in your area.

What to Consider When Looking for a New PCM

Shopping for a new PCM can quickly become overwhelming because of the wide variety of options on the market. To help you choose the right one for your vehicle, here are some factors to consider when you’re in the market for a PCM replacement:

Application

Always check for fitment before buying a new PCM for your vehicle. Get a replacement that’s designed specifically for your vehicle’s year, make, and model to guarantee a perfect fit and hassle-free installation. If you’re unsure, refer to your PCM’s replacement part number. It’s usually on the PCM itself or in your manufacturer’s catalog.

Condition

PCMs are available in new and remanufactured conditions. A new PCM is built from brand new components and materials, while a remanufactured PCM is an old but still perfectly usable module that underwent a thorough upgrade process that lets it compete with new parts.

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If you’re on a budget, a remanufactured PCM will help you save money without downgrading your car’s performance.

Quality

Make sure to pick a PCM that’s made of durable and made of high-quality materials. Otherwise, you might find yourself in inconvenient or dangerous situations, like your car suddenly shutting down in the middle of driving.

The best way to ensure the quality of your new PCM is to order it from a trusted brand.

Finding the perfect replacement PCM for your vehicle should be easy as long as you follow the tips listed above and look through credible product reviews. Also, don’t forget to check your vehicle specifications or consult your trusted mechanic to double-check the specifications of your replacement PCM.

How to Find a Competitively Priced Powertrain Control Module For Your Car

Replacing a bad powertrain control module isn’t something you can put off. It can lead to more serious engine issues that could cost even more to resolve. Fortunately, you can order a new PCM at CarParts.com with only a few clicks.

At CarParts.com, we make shopping for powertrain control modules and other auto parts a breeze. Enjoy easy navigation through our website, thanks to our integrated vehicle selector that will help you find the most suitable PCM. You can count on round-the-clock support from our friendly and helpful customer service team, who can answer any question you might have about our products.

Don’t let a bad PCM render your vehicle undriveable. Take a look at our wide array of competitively priced powertrain control modules at CarParts.com and shop for one that fits your needs and budget now.

About The Authors
Written By Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Contact Center Manager and Technical Reviewer at CarParts.com

William “Bill” Guzenski has produced hundreds of how-to videos for the automotive community. He’s an ASE Certified Master Automobile Technician, and is affiliated with the Specialty Equipment Market Association (SEMA). He loves attending race events and car shows throughout the country, as well as traveling in his 40-foot motorhome, exploring abandoned mines and ghost towns.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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Clifton Shegog

My car is a Nissan Altima 2.5. recently after being hit on the passenger front above the wheel well, it began to sound as though it was running on diesel. It shake upon starting, and continues to sound rough. The check engine light comes and goes off. I changed the relays in the engine ECM to no avail. What is my problem?

Clifton Shegog

The above comment should add that it’s a 2005 Nissan Altima.

Larry Fowler

2004 BMW 745li Engine Control Module

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