Updated at: 27-08-2022 - By: Lucas

Automobile computers and electrical components, as you may be aware, are commonplace in today’s vehicles. An important part of your driving experience is the PCM.

Being a better car owner means knowing your vehicle through and out, and that starts with understanding what a PCM is and what it performs.

Understanding What Is A PCM On A Car?

What Is A PCM On A Car

One of the most important parts of a car’s computer is the Powertrain Control Module (PCM). Since the PCM is named after your powertrain, it is in charge of managing everything from the engine and transmission to the rest of the driveline.

Engine Control Unit (ECU), also known as Engine Control Module (ECM), is a term you may have heard before. A separate computer is used in some vehicles, although it is part of the PCM in others.

The Transmission Control Module, or TCM, is another term you may be familiar with. The PCM includes this as well. Both the ECM and the TCM collaborate to keep your automobile running smoothly at all times.

How Do They Work?

What does a car’s PCM stand for?

For that, you must first understand how it operates.

With the help of several sensors, your car’s Engine Control Module adjusts the engine settings to provide a smooth ride. The exhaust, cooling, and intake systems, among others, provide data to the ECM.

After that, the engine settings will be adjusted properly.

As an illustration, if your engine isn’t getting enough air, the Engine Control Module will lower the fuel so that it burns completely. The ECM is also able to manage the camshaft, throttle position, and ignition timing, among other things.

The Transmission Control Module (TCM), like the ECM, is responsible for a wide range of functions in a car. The Transmission Operate Module, like the Engine Control Module, uses data from sensors in your car to control the transmission.

When it comes to autos, just the TCM is used, whereas the ECM is only found in automobiles with manual transmissions.

The ECM, for example, is responsible for rev matching in many sports vehicles. During shifts, it uses data from the ECM to automatically match the clutch and engine speeds. The speed of the car and the engine are taken into account by older TCMs when determining whether to shift gears.

This includes data from cruise control, throttle control, and the traction system on modern models. As well as determining when to shift, modern TCMs assist prevent wheel spin and gear hunting.

What is the purpose of a PCM in a car?

Does the PCM use the TCM and ECM systems to control the drive train?

Better fuel efficiency and performance are the results of this system’s integration of the two systems.

It is possible to ease the throttle a little when the transmission is ready to downshift, for example, in order to make the downshift a little smoother. However, the PCM is also responsible for a number of other tasks. Let’s have a look at some of the PCM’s other capabilities.

Ignition timing

The PCM has the ability to alter the timing of a spark plug’s ignition. Based on your throttle control, it optimizes the fuel economy or performance accordingly.

Idle speed

Idle RPM is controlled by the PCM so that when you turn on your air conditioning while parked, the engine revs to meet the additional energy demand. In order to avoid wasting fuel, the PCM regulates it.

Air to Fuel ratio

The PCM will alter your engine’s air-to-fuel ratio based on data from the Engine Control Module. The optimal air-to-fuel ratio is 14.7 grams of air per gram of fuel under most circumstances.

The PCM will do its best to meet the manufacturer’s recommended fuel ratio, which varies depending on the vehicle and type. However, this is not a ratio that will always be possible. To keep the engine from stalling, the PCM will attempt to make up for the incorrect ratio it senses.

Error Monitoring

The PCM serves a very significant purpose in this regard. Your car’s PCM (powertrain control module) will attempt to fix any problems it discovers. However, if it is unable to resolve these faults, the check engine light will illuminate to notify the driver.

Even if your PCM senses that your engine isn’t drawing in sufficient oxygen from the air, it can diagnose the problem by using the mass airflow sensor’s information and alert the driver to this fact.

There are three possible causes for the Check Engine light to turn on. speedy, sporadic, and constant. There is a little problem with the engine if the Check Engine light remains on. One of the most common causes of intermittent, fast flashing lights is a malfunction with the engine’s ignition system.

Tow your vehicle to the nearest service station immediately if you’re in this situation. If you keep driving, you run the risk of doing more harm to the engine.

Powertrain Control Module failure

What Is A PCM On A Car-2

PCMs, for all their speed and intelligence, can be rendered useless if they develop a malfunction. It’s possible that the PCM won’t get the data it needs to work properly if a sensor is malfunctioning.

In many cases, the PCM will be unable to correct minor issues, allowing larger issues to occur. Here are some of the most prevalent issues that arise when sensors or the PCM fail.

The PCM, ECM, and TCM are all geared toward extending the lifespan of the car. Premature deterioration can be caused by internal component wear and corrosion. There may be some variation in the mileage at which a particular vehicle’s components wear out, depending on the manufacturer’s design and build quality.

Even if you’re driving a new car, you’re unlikely to suffer PCM damage. There are, however, a few things to keep an eye on.

Engine not turning on

The automobile may not start if the PCM is malfunctioning. No matter how hard you try, the engine will not begin to run. As a result, the machine crashes due to the malfunctioning PCM’s inability to transmit the right signals and commands.

The ignition system, for example, may not be able to determine when to fire the correct cylinder if the PCM is malfunctioning. The engine will not start if the ignition system is not working correctly.

There are, of course, numerous reasons why your car won’t start. If your car won’t start, attempt the usual methods of troubleshooting. Your PCM may be defective if none of the repairs you’ve tried have solved your problem.

Poor fuel economy

The PCM, as previously established, has the ability to regulate the amount of fuel delivered to the engine. When the PCM malfunctions, the engine’s fuel level is given false information.

For example, if an injector is injecting more fuel than is necessary, the PCM will not lower the amount of fuel being used. Fuel usage is reduced as a result.

Of course, there are many additional reasons that can cause the engine to use more fuel. Incorrect tire pressure, incorrect oxygen sensor, insufficient mass airflow, bad spark plugs, ineffective injectors, etc.

Check Engine Light And Error Codes

When the PCM detects a problem with the drivetrain or transmission that it cannot resolve on its own, an error code is generated. When an error code is detected, the check engine light will blink to alert the driver.

In spite of this, a malfunctioning PCM may show incorrect error codes or register an error code when there are no issues.

The error code can be found by using an OBD 2 scanner to connect to the car’s computer. Your computer will then be scanned by an OBD 2 scanner, which will provide an error code. Code P0301, for instance, denotes a cylinder misfire.

You may have a bad PCM if you don’t have any misfire problems, but if you have, then you have a faulty PCM. Keep in mind that a defective sensor could be to blame for this issue.

You can, however, narrow the problem down to either the PCM or a defective sensor once you have confirmed that there is no problem with the car.

Engine Misfires And Stalling

A malfunctioning PCM will have a negative impact on the machine’s performance because the PCM controls the engine. While driving, it may not turn on at all, or it may suddenly halt and turn off completely. Your engine may not be working for a variety of causes, just like any other symptom on this list.

A faulty spark plug that does not ignite properly can be the cause of a bad engine ignition. A malfunctioning mass airflow sensor or a clogged air intake can lead to an engine shutdown, which is typically caused by insufficient air supply to the engine.

If you try to fix the problem on your own, it will take a long time. However, if you’re trying to save money, this is an alternative to consider.

There is always a trend when it comes to automobile problems. As an example, a clogged air intake might limit how fast the engine runs. Having a clogged air intake prevents the engine from getting the air it needs to run at high RPMs, resulting in a lack of ignition.

PCM issues, on the other hand, are frequently more unstable and do not follow a predictable pattern. It’s a safe bet that your PCM is to blame if your engine suddenly behaves in an odd way.

What Do You Do If Your Check Engine Light Flashes?

What Is A PCM On A Car-3

When a fault is discovered in the transmission, the PCM and the check engine light work together to notify the driver. Is the check engine light still lit?

You should, of course, pull over as soon as the check engine light comes on, as previously stated. This is a critical issue that, if not addressed, might lead to engine failure.

If the light is solid and not flashing, don’t be alarmed; you can continue driving as long as you address the problem quickly. Checking the gas cap is the quickest and most straightforward initial step. This is because if the cap is loose, the check engine light could turn on. Tighten the lid as necessary if it is too loose.

Unplug and replug the machine. Turn the ignition on and off three times in succession if the check engine light is still on, and then remove the check engine light.

If, on the other hand, the light continues to flash, you may need to utilize an OBD 2 scanner to determine the source of the problem.


Listed below are a few frequently asked questions about what a car’s PCM actually does.

Where Is The PCM Located In A Car?

A car’s PCM can be installed virtually anywhere. It can be found in a variety of locations. The engine compartment is the most typical place to find one. You might notice that it’s covered near the windshield on some models.

Can You Reset Your PCM?

PCM malfunctions may necessitate a reset of the device. The question is whether or not this will work. Even though it may not work, it is worth a go if it is an electrical problem.

Disconnecting the battery is the quickest and easiest way to reset your PCM. Removing the battery’s cables and waiting for around five minutes should do the trick. Your car will now start once you’ve reconnected the battery. This should re-boot your PCM.


System that coordinates the Engine Control Module and the Transmission Control Module to enhance fuel efficiency and make the vehicle run as smoothly as possible is known as a powertrain control module. The control and responsiveness of the throttle power will also be excellent.

Using sensor data, the Powertrain Control Module can not only warn you to most automobile mechanical problems, but it can also help drivers fine-tune engine settings to suit their tastes.

Due to obsolete software or wear and tear, PCMs might fail even though they are designed to endure a long period. You may notice irregular behavior and misleading error codes if they fail. Such an issue may necessitate a thorough investigation of the problem.

You should also replace the PCM if it is the source of the problem. The cost of replacing a Powertrain Control Module (PCM) can range from $1250 to more than $2000 depending on the complexity of the vehicle’s engine and gearbox systems.

Driving without a working PCM will cause more harm than benefit. If you don’t have any other options, a replacement is the only option you have.