How to Tell if Your Engine Control Module (ECM) is Failing

What’s an Engine Control Module (ECM)?

If your car had a brain, the ECM would be it.

The Engine Control Module (ECM), also known as the Engine Control Unit (ECU) or Powertrain Control Module (PCM), is one of the most critical components found in modern vehicles. This piece of equipment essentially acts as the main computer system for many of the vehicle’s engine performance and drivability systems. The various sensors in the engine relay information to the ECM and that information is used to calculate and tune engine spark and fuel for maximum efficiency and power. In laymen’s terms, if your car had a brain – this would be it.

image of dashboard speedometer, tachometer with illuminated check engine light.

That little light could mean big trouble.

Since the ECM is such a critical piece of equipment, when it begins to fail, the car may become undrivable altogether. When problems arise with the ECM, there are some key symptoms to alert you to the situation.

Signs of a Bad ECM

Check Engine Light Is Illuminated

A check engine light does not immediately indicate a problem with the ECM, however, it always indicates an issue with the engine. Sometimes, this light can be triggered when there are no issues present, but a simple test will determine which error codes are being thrown. A mechanic will be able to tell you if there is an issue with your ECM or another component.

Engine Stalling or Misfiring

Erratic engine behavior is another common symptom of a bad or failing ECM. A faulty computer can also be responsible for engine stalling or misfiring, though this tends to be more intermittent. These symptoms may come and go, and may appear to have no pattern to their severity or frequency.image of computerized diagram of car.

Engine Performance Problems

When the ECM is faulty or failing, it will throw off the timing of fuel settings of the engine. You may notice unexplained drops in fuel efficiency, or you may feel your vehicle struggling to shift. Any sudden change in your vehicle’s performance is reason enough to seek out the source of the problem.

Related: What Are Car Diagnostics and What Do They Do?

Car Won’t Start

Another common symptom of a bad or failing ECM is a vehicle that will not start or struggles to start. If the ECM fails entirely, your car is left with no engine management control system, and as a result will not start. The engine may crank, but will not start without the vital inputs from the computer.

Related: What’s In a Tune-Up?

What to Do If You Think the ECM is Failing

Other systems might be causing deeper problems that need investigation.

Get your car checked by an expert mechanic.

image of aamco mechanic showing customer engine under hood, hood up.

“See, it’s the ECM.”

It is important to note that all of these symptoms can be symptoms of other system failures or issues with your vehicle. But, since the ECM plays such a vital role in the performance of the vehicle’s performance, any issues which arise can be catastrophic to the engine. Computer systems found in modern cars are extremely complex, sophisticated, and complicated – this makes it tricky to diagnose and troubleshoot computer related problems.

If you suspect that your ECM is the source of your worries, you should have the vehicle inspected by a trained professional. Catching this issue early on can save a lot of money and stress. Replacing this part can be a major expense, but fortunately, an ECM can be repaired or reprogrammed in many cases. This prevents you from having to replace the part entirely.

At AAMCO Colorado, we want to help! If your car has experienced any of the symptoms noted above, you may want to get ahead of the situation by identifying problems early on and getting them fixed. Book an appointment with your local Colorado AAMCO automotive maintenance and repair center today.


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