Understanding Power Train Control Module

PCM (Powertrain Control Module), ECU (Engine Control Unit), and ECM (Engine Control Module) are all interchangeable generic acronyms for the same thing: a control unit for the engine/transmission system.

Manufacturers, vehicle sales, mechanics, auto technicians, electronic engineers, and the general public will frequently use various terms depending on who is speaking. There are, however, distinctions between these electrical modules and the functions they perform on the vehicle.Powertrain Control Module

Well, in this article, we’ll be talking about the power-train control module. Even so, the answers to the following questions will be addressed:

  • What is a power-train control module and its functions?
  • Where is the Powertrain control module located?
  • What are the symptoms of a bad power-train control module?
  • How much does the power-train control module cost?

So, let’s get to discussing!


What is a power-train control module and its functions?

A power-train control module (PCM) is an automotive component, or control unit, found in vehicles. In most cases, it is a combined controller that includes both the engine control unit (ECU) and the transmission control unit (TCU). On some vehicles, such as many Chryslers, there are three separate computers: the PCM, the TCU, and the Body Control Module (BCM).

In general, these automotive computers are quite dependable. In most cars and trucks, the PCM regulates more than 100 variables. There are hundreds of error codes that might arise, indicating that a component of the vehicle is malfunctioning. When one of these mistakes happens, the “check engine” light on the dashboard normally illuminates.

The PCM is one of the numerous onboard computers that serve as the engine control system’s “brain.” The principal inputs to the PCM come from a variety of sensors located throughout the vehicle. The majority of them are concerned with engine management and performance. These sensors fail far more frequently than any of the computers.


The PCM is the engine’s power delivery unit’s brain. It regulates a variety of functions such as ignition timing, fuel delivery, emissions, turbo boost pressure, idle speed, throttle control, and much more. While you may have heard of a Transmission Control Module (TCM) or an Engine Control Module (ECM), a PCM is in charge of both.

So, if your car has a PCM, it either stores both of those components in a single unit or manages both operations through a single computer. The PCM manages all of these functions via a network of sensors. It begins by sending a command to an actuator and then measures the actual consequences via a sensor.

The PCM is programmed to instruct each actuator what to perform when certain directives are satisfied, such as when the throttle is depressed, and it is also programmed to know what acceptable readings are in response. When anything isn’t working properly, it sends a warning signal to the driver via the check engine light. It’s not an easy component to comprehend, and you won’t be able to fix it unless you have the proprietary software.

Where is the Powertrain control module located?

Powertrain Control Module Location

The PCM is usually positioned in the engine bay near the fuse box or inside the automobile near the fuse box. It’s also common to find it behind various covers under the front windshield. The manufacturer can install your vehicle’s PCM in a variety of locations, but the most frequent is in the engine compartment.

The PCM appears to be little more than a metal box with few wires protruding from it. If your vehicle’s PCM is not in the engine compartment, it could be in the passenger compartment. While this isn’t commonplace, if it exists, it’s usually underneath the passenger side dashboard, under all the plastic coverings.

In the extremely unlikely event that your PCM isn’t in either of those locations, it could be in your vehicle’s trunk. This is less common because all of the cables from the engine must run to the rear of the vehicle to connect with the PCM.

What are the symptoms of a bad power-train control module?

Here are the most common symptoms of a bad powertrain control module:

  • Poor performance
  • A Check Engine Light
  • Issues starting the car
  • Poor Fuel Economy
  • Shifting Issues
  • Increased Emissions

Poor performance

Because your PCM is in charge of performance, it stands to reason that if it isn’t functioning correctly, performance will suffer. The more messed up your PCM is, the more probable it is that you will have several issues resulting in poor performance. However, if only a single component of your PCM is malfunctioning, you may only experience poor performance under particular conditions, such as idling or accelerating.

A Check Engine Light

A check engine light is usually the other most common symptom that your PCM is malfunctioning. The light could be for anything to do with the engine. Keep in mind that the issue is most likely with the sensor, wiring, or anything else. Before going to the PCM if your car has a check engine light, rule out all other possible causes. Using an OBD2 scanner, check the issue codes.

Issues starting the car

If your PCM problems get severe enough, you may be unable to start your vehicle. At the very least, it may be difficult to start, especially in cooler weather. If your car isn’t starting and it’s due to a problem with the PCM, it’s a major issue that you should get checked into before you total it.

Poor Fuel Economy

It’s hardly unexpected that if everything isn’t working properly, your fuel efficiency would drop. For example, if your turbo isn’t producing enough boost because the PCM isn’t telling it to, you’ll need to accelerate more. There are other cases like this, but with a defective PCM, you will most certainly waste fuel.

Shifting Issues

If your car is experiencing trouble shifting into different ratios, the PCM could be the culprit. Your PCM is in charge of everything your engine and transmission do. So, if you’re having problems with your powertrain, you might be able to pin them down to the PCM. If your car is suffering from shifting issues, you should have it checked out right away. Otherwise, your vehicle would behave unpredictably, potentially leading to an accident.

Increased Emissions

When everything is working properly, your PCM reduces emissions by optimizing performance. When something isn’t working as it should, performance degrades, and emissions likely rise. However, until you take your vehicle in for an emission test, you won’t notice any difference.

How much does the power-train control module cost?

The PCM is a computer, and replacing computers is not cheap. As a result, depending on the car type and labor expenses, the average PCM replacement cost ranges between $800 and $1,500. Worse, this is virtually entirely due to the expense of the PCM itself. Labor is normally between $75 and $100. However, if you believe you can save $100 by replacing it yourself, think again.

Related Article

Watch the video below to learn more


What does the powertrain control module do?

The PCM regulates ignition timing, fuel delivery, valve timing in VVT engines, emissions functions, turbo boost pressure in turbocharged engines, idle speed, throttle position, and cruise control.

What are the symptoms of a bad powertrain control module?

  • Poor performance
  • A Check Engine Light
  • Issues starting the car
  • Poor Fuel Economy
  • Shifting Issues
  • Increased Emissions

Is PCM the same as ECU?

PCM (Powertrain Control Module) – This is a combined engine and transmission control unit that manages and functions the engine and transmission from a single unit. The engine control unit (ECU) / engine control module (ECM) is an electronic control device that only manages the engine.

What is the difference between ECM and PCM?

ECM stands for the engine control module. The PCM stands for the powertrain control module. ECMs are in charge of engine regulation. PCMs are in charge of powertrain control.

Can a car run without a control module?

If the ECM fails fully, the car will lose engine management control and will not start or run. The engine may still crank, but it will not be able to start without critical computer inputs.

What causes control module failure?

The module is receiving an excessive amount of voltage. Connections between modules have disintegrated. Sensor failure. Particularly high engine temperatures.

How do I check my powertrain control module?

You should inspect the sensors attached to your PCM as well as the connections that link them. If you encounter a PCM code – or two, or three – it can greatly assist you in determining which sensors or wiring are bad. Perform a visual inspection of these wires as well as a multimeter test.


Ultimately, the Powertrain Control Module (PCM) is a vital component in current automobile technology, acting as the brain of the vehicle’s powertrain system. Its principal job is to manage and control numerous aspects of engine performance, transmission, and emissions control, assuring optimal functionality and fuel efficiency while limiting harmful emissions.

And that’s it for this article, in which we talked about the Powertrain Control Module (PCM). With that being said, the answers to the following questions have been discussed:

  • What is a power-train control module and its functions?
  • Where is the Powertrain control module located?
  • What are the symptoms of a bad power-train control module?
  • How much does the power-train control module cost?

Hope you learn a lot from the reading. If you do, kindly share it with others. Thanks for reading; see you around!

Write A Comment