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Last updated on October 31st, 2024 at 01:02 pm

The powertrain control module (PCM) is the brain of every modern car. PCM is sometimes used interchangeably with ECM (engine control module), although the two have some differences. The PCM generally includes both the engine control unit (ECU) and the transmission control unit (TCU). Problems with the PCM can result in various car performance issues and erratic behavior.

While your car may still run despite PCM dysfunctions, it is crucial to repair or replace damaged PCMs as soon as you notice them. A functional PCM can help you diagnose various engine performance issues. A faulty one, on the other hand, can be the cause of different problems. Here is a brief look at some of the most common symptoms of a lousy PCM:

Check engine light is on

The check engine light comes on as a warning that should prompt various test trouble codes. When this light shows in your dashboard, it usually spells problems with the ECU. The mechanic will first reset the error code and ensure the indication isn’t false and the sensors are in the proper working conditions. The next phase involves diagnosing where the problem is based on procedures indicated in the code.

If everything in your car is good, but the check engine light is on, your PCM might be damaged. You can replace the damaged part or entire unit depending on the scale of damage. Bad PCM shouldn’t be a cause for worry, though, and many states allow drivers to pass checks despite the engine light is on. Nonetheless, the sooner you fix it, the better your engine will perform and you can also protect other parts and systems that could get compromised.

Bad PCM Causes Engine performance issues

Engine misfiring or stalling and overall poor engine performance are common indications of problems with the engine control unit. Modern vehicles have various sensors that operate within a given range to ensure the intended functions of the engine. A faulty computer within the engine management unit may result in erratic engine behavior and unpredictable symptoms that come and go with no real pattern.

Issues in the ECU can also throw off fuel settings and timing, resulting in reduced engine performance, power, acceleration and fuel efficiency, among others. If you notice problems with performance, bad engine computers may be the issue. This may also cause random shifts and transmission issues caused by faulty sensors.

• The car does not start

Ignition failures can stem from a myriad of issues ranging from bad batteries to mistimed fuel injection and bad engine computers. The ECU is responsible for engine management control, so if it fails, your car won’t get the required inputs to start. If the computers fail to send valid data, the vehicle may still crank but won’t start. In some cases, the car will require several attempts to get running, which can be frustrating.

You should get a comprehensive diagnosis from an experienced mechanic to ensure PCM (powertrain control modules ) error isn’t the reason your car starts roughly. Failing ignition is a severe problem, considering you aren’t sure when next it might fail. As such, you need prompt troubleshooting. Common causes of failed ignition include improper fuel-air ratio balance, bad engine timing and a short in the wiring band.

•     The car produces dark or too much smoke

If you failed your emission test, chances are you have a bad PCM. The engine control module is responsible for balancing the fuel-to-air ratio, so if it is faulty, it can result in various inefficiencies. For instance, if there is too much fuel compared to air (the mixture is too rich), the combustion process won’t be complete resulting in more carbon monoxide and other un-combusted compounds. A failed emission test can also stem from a damaged catalytic converter, which is more expensive to replace compared to ECU replacement costs.

You should always check the emissions coming out of your engine. If the smoke is dark, this could be from an engine oil leak, burnt gasket and other potentially serious issues. Nonetheless, failing ECMs aren’t the only cause for irregular emissions, so it is recommendable to get a full diagnosis.

1.     Fuel inefficiency loss of mileage

Sudden loss of gas mileage should call for PCM diagnosis. The PCM regulates the fuel-to-air ratio and informs the engine when to shift gears. Whenever this function has errors, you will lose gas mileage, although there are several other reasons for this symptom. Faulty ECMs may result in wasteful combustion patterns and ultimate fuel efficiency. If the engine doesn’t know how much fuel to combust or the car has transmission issues, it will use up more to complete a shorter distance. It is essential to monitor your car’s fuel consumption.

Conclusion

There are several other symptoms of faulty engine management control. For some, it is the simple error code that is logged when your engine computer has issues. Since bad PCM symptoms are can be caused by other car issues, you should get a qualified mechanic to check your car and restore the computers to normal working conditions. PCM issues can result in more serious damages, so it is recommendable to resolve them as soon as you can. These bad PCM symptoms are worth knowing.

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