Skip the auto shop - Our mechanics make house calls
  1. Home
  2. Articles
  3. Symptoms of a Bad or Failing Engine Control Module (ECM)

Symptoms of a Bad or Failing Engine Control Module (ECM)

check engine light

The engine control module (ECM), also commonly referred to as the engine control unit (ECU) or powertrain control module (PCM), is one of the most important components found on virtually all modern vehicles. It essentially functions as the main computer for many of the vehicle’s engine performance and drivability functions. The ECM takes the information from the engine's various sensors, and uses that information to calculate and tune engine spark and fuel for maximum power and efficiency.

The ECM plays a crucial role in newer vehicles, where many (if not all) of the essential functions of the car are controlled by the ECM. When the ECM has any issues, it can cause all sorts of problems with the vehicle, and in some cases even render it undriveable. Usually a bad or failing ECM will produce a few key symptoms that can alert the driver of a potential issue.

1. Check Engine Light comes on

An illuminated Check Engine Light is one possible symptom of a problem with the ECM. The Check Engine Light usually illuminates when the computer detects a problem with any of its sensors or circuits. There are cases, however, where the ECM illuminates a Check Engine Light mistakenly, or when there is no issue present. Scanning the computer for trouble codes can help reveal if the issue is with the ECM, or elsewhere on the vehicle.

2. Engine stalling or misfiring

Another symptom of a bad or failing ECM is erratic engine behavior. A faulty computer may cause the vehicle to intermittently have issues such as stalling or misfires. The symptoms may come and go, and may not appear to have any sort of pattern to their frequency or severity.

3. Engine performance issues

Engine performance issues are another symptom of a possible problem with the ECM. If the ECM has any issues, it may throw off the timing and fuel settings of the engine, which can negatively affect performance. A faulty ECM may cause the vehicle to experience a reduction in fuel efficiency, power, acceleration.

4. Car not starting

Another symptom of a bad or failing ECM is a vehicle that does not start or is difficult to start. If the ECM fails completely, it will leave the vehicle without engine management control, and will not start or run as a result. The engine may still crank, but it will not be able to start without the vital inputs from the computer. This symptom can also be caused by a wide variety of other issues, so it's best to get a complete diagnosis by a professional technician to accurately determine the cause.

Because the ECM plays such a vital role in the performance of the engine, any issues with it can cause major problems with the overall functionality of the car. As the computer systems found on modern vehicles are quite sophisticated and complicated, they can also be difficult to diagnose. For this reason, if you suspect that your vehicle’s ECM is having an issue, have the vehicle inspected by a professional technician, such as one from YourMechanic, to determine if your car will need an ECM replacement.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Still not sure about your car's issue?
Diagnose your car
What kind of issue are you experiencing?
Brakes are squeaking
Car is not starting
Car is overheating
Car is shaking (vibrating)
Fluids are leaking
Heating and A/C
Smoke or steam is coming out of the car
Warning light is on
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

How Long Does a Vacuum Brake Booster Check Valve Last?
The braking system on your car requires a lot of pressure. The vacuum booster is one of the main sources of this pressure. This booster will take the pressure that...
How Long Does a Throttle Return Spring Last?
Not all vehicles on the road feature an electronic throttle control (ETC), which is also called drive-by-wire. For vehicles that don't offer this system, they have a throttle cable instead that...
Symptoms of a Bad or Failing Flexible Clutch Hose
Common signs include difficulty shifting, low clutch fluid, and feeling no resistance at the clutch pedal.


Related questions

Q: possible bad ecm if I reset it will that help me in finding out if its bad.

Hi there. From the description you provided, it is unlikely, the ECM (electronic control module) is at fault. First and most important, when disconnecting the battery, always disconnect the negative terminal first and reconnect last. Starting with the positive terminal,...

Q: Bank 2 Sensor 1 PA03(?) code. Range performance issue?

Hello. The code you have provided is not a valid automotive error code that I recognize. Based on your context I think it may be possible that there is an issue with the signal range of one of your oxygen...

Q: Whistling noise when shifting gears

Hello there, thank you for asking about your 1989 Buick Reatta. Your gas mileage will vary depending on what kind of driving you're doing. It's possible the first week you did mostly highway driving, while the second week you stayed...