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Auto Electrical

How to Know If You Have A Faulty ECU (Computer)

The ECU, also known as the computer, DME or ECM, is the main unit that controls your motor and allows it to run. When it starts to fail, your car won’t run right, or might not run at all. Here is why and how it fails, and how you can find out if that’s the problem.

How to Tell If You Have a Faulty ECU (Computer)

Common Symptoms ECU Failure
When your ECU starts failing, you will usually notice at least one of the following symptoms (sometimes more than one):

  • Check engine light comes on
  • Erratic idle
  • Engine turning off for no reason (stalling)
  • Intermittent starting problems
  • Overheating ECU
  • Connection issues between the ECU and the diagnostic scanner
  • Engine won’t start at all
  • Excessive fuel usage
  • Poor running condition of the motor

If you are experiencing any of these issues with your car, the first step you should take is to get the car scanned with a diagnostic tool. This will reveal if the ECU has produced any error codes and may tell you if the ECU is having problems or has failed. However, if the ECU has completely died, the scanner won’t be able to scan anything. This itself can be a sign that the ECU is dead.

If the scanner was unable to connect with the ECU to do a scan, the next step is to test to ensure the ECU is still plugged in properly and that it is getting a strong power and ground signal. This simple test can be done with a multimeter once you know which pins should be getting power and ground on the ECU plug (a simple internet search should tell you for your particular car).

If it is getting power and ground, the best test is to get a known working ECU and replace yours to see if that fixes the problem. If it does, you’ve had a bad ECU. If it doesn’t, the issue lies elsewhere.

Keep in mind that if this does fix the problem, it may pay to get the car checked out, because there was a reason the ECU died in the first place. You don’t want it to happen again.

If you are not getting power and ground, something else is causing the problem, such as a fuse or relay. Diagnosing this can get complicated fast, so unless you have experience it is probably best to go see an auto electrician.

If the scan revealed issues with the ECU, then you’ve got your answer and will have to replace the ECU.

If you are having electrical problems with your car, come and see us at Eurosparx. We have the latest tools and equipment to scan and diagnose all European and Japanese vehicles and can have a look at yours to let you know if you need a new ECU or if it can be repaired.