5 Causes of Engine ECU Failure or Not Working Properly

The ECU is the engine control unit of your vehicle. It is also often referred to as the PCM (powertrain control module) or ECM (engine control module).

This electronic module is a built-in computer which your vehicle depends on for managing a variety of its systems and functions. Think of it as the vehicle’s brain. The engine and drivetrain are the most dependent on the ECU.

Through a numerous array of electronic sensors, chips, and components within the vehicle, the ECU can transmit data feedback to the engine. The nature of this feedback will determine which function the engine will perform next.

This helps a great deal with calculating the proper amount of air and fuel needed for the internal combustion process. That way, better fuel efficiency can be achieved.

Top 5 Causes of Car ECU Failure

The ECU regulates virtually every important system and function in your vehicle. If you were to ever have a bad ECU, then many noticeable symptoms would present themselves. It wouldn’t take you long to realize the ECU was responsible.

However, what you may wonder about is why the ECU malfunctioned in the first place. There are lots of internal causes which could contribute toward this. Below are the top 5 causes of a bad ECU. Investigate them as soon as you notice problems with the ECU.

Read also: Car Immobilizer: Basic Function and Bad Symptoms

1) Dead Battery

Car batteries have electronic cells which need to function in order for the ECU to function. If any of the cells in your car battery are dead, then your ECU is going to fail soon afterward. Once all the cells are dead, your entire vehicle won’t be able to function either.

You won’t be able to even start your vehicle and get the engine running. So, look out for the early warning signs of a malfunctioning ECU and then have your battery examined right away.

2) Corrosion

The ECU has seals around it which are supposed to prevent moisture from entering inside. However, after a number of years, these seals tend to become worn out. If the seals become too worn, it will be easier for moisture to pass through them and enter the ECU.

Moisture is a bad thing to have in an ECU because corrosion will form on its components. If the corrosion is not cleaned away quickly, it will cause these components to get damaged. Then you will have a malfunctioning ECU.

3) Low Voltage

The average ECU is expected to have at least 9 volts, but preferably 12 volts. There is wiring that runs into the harness of the ECU where you can check the voltage amount.

All you need to do is connect a voltmeter gauge to it. This device will be able to detect how much voltage is running through the ECU. If the voltage is 6 or less, then this is likely causing your ECU problems.

4) Bad Jump Starting

Whenever a jump start is performed on your battery, you need to ensure that the jumper cables are attached properly. If you perform a jump start with the cables attached incorrectly, then it could short out your ECU by causing it to spike too quickly.

This will require you to get the ECU repaired or possibly even replaced. This will end up costing thousands of dollars in expenses.

5) Bad Starter

Many vehicles have starters with their own sensors in them. One of these sensors is the override sensor which manages how many volts the ECU will receive.

If this sensor were to go bad, then the ECU would not receive the correct amount of voltage. Then it would malfunction and cause further problems in your vehicle.

Another problem that could happen is if you replace your starter with a new starter that is not compatible with your vehicle’s ECU. Make sure any new starter that you purchase has the right sensors which can communicate with the ECU properly.

2 thoughts on “5 Causes of Engine ECU Failure or Not Working Properly”

  1. I have an intermittent ECU problem that seems to happen mainly in the morning when the headlamps are on , any ideas ?

    • I’m sorry to hear the problem is intermittent. Those can be very tricky to diagnose.

      It’s hard to throw out too many ideas without more information. Providing your year/make/model and a description of the symptoms would help narrow down the cause tremendously.

      Before jumping straight to the ECU, I would start with the simple stuff: have your battery and alternator tested at a local parts store. Most places will do this for free.


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