Tips and Tricks

What is a Powertrain Control Module (PCM) and when to replace it?

Wondering what a powertrain control module (PCM) is? Depending on the make or model of a vehicle, there are different systems installed for a computerized control of the car’s engine, transmission and other components.

The Powertrain Control Module is a computer that especially monitors and manages engine-related functions such as the ignition system, fuel injection, exhaust system and so on. Sometimes, it may also control the anti-lock brake system and the traction control system.

This computerized system helps engines run efficiently and the main advantage that the PCM gives to the drivers is through the check engine lights and other warning lights on the instrument panel that warn him of an oncoming accident before it actually does.

Powertrain Control Module (PCM)

It might come as a surprise to you, but over 50% of the PCMs that are returned while they are still in warranty, have nothing wrong with them. This is because people have the habit of blaming the computer system whenever something goes wrong with the engine.

Before you decide that the PCM has become useless, you need to get it tested and verified. So a good idea is to not even think of replacing the PCM unless you have diagnosed the problem for sure and know that replacing the PCM is the only way to solve this problem.

When do you replace the PCM?

Generally, there are two reasons in which you have no option but to return the PCM. While there can be a few other cases as well, these tend to be the most common reasons.

  1. Voltage Overloads

If there is a short in the solenoid or the actuator circuit and it is not detected and repaired on time, then the voltage overload that it creates will kill the PCM leaving you with no option but to go for the expensive replacement. Moreover, even after replacing the PCM, it has high chances of getting killed again if the basic problem of the short is not detected.

So a just mindless replacement will not be helpful and will lead to more expenses. That is why we recommended a complete and thorough diagnosis in the first place, remember?

  1. Environmental Factors

One of the most important things that must be kept away from the PCM is water. If water gets inside the PCM, it will cause short circuits and corrosion and ruin it completely. That is why manufacturers won’t even bother repairing a PCM that has been taken out of a car that had been submerged in water. They will suggest replacing it.

Other environmental factors such as vibrations and thermal stress can lead to micro-cracks. This generally happens due to the rough designing of the circuit and the operation of the vehicle. However, in some cases, this problem of micro-cracks can be rectified.


There are several kinds of PCMs available in the market today. You must correctly identify the PCM along with its replacement to avoid unnecessary and hassling returns later on.

Just because they all look similar on the inside, doesn’t mean their settings on the inside are identical as well. And oh, getting a PCM that is similar to the existing one won’t do. It has to be the same. The exact same.

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