5 Signs of a Faulty ECU

As its name suggests, your car’s electric control unit (ECU) or electric control module (ECM) controls the electronics in your car. In the modern day, that means your automatic transmission, parts of your engine, your car battery, and a wide variety of other systems. Because your ECU is attached to so many systems, it often gets overlooked a the cause of your car issues. Unfortunately, a bad ECU can cause snowballing car issues later down the road. If you start to notice these warning signs, consider asking your mechanic to take a look.

Your Car Won’t Start

A bad ECU can easily prevent your car from starting. Unfortunately, since there are so many other reasons your car could not be starting, it’s hard to diagnose a bad ECU immediately from this problem. First, check that your starter is working, your car battery is charged, and you have enough gas in the car. If everything else is working fine, but the car still won’t start, it’s probably the ECU.

The Check Engine Light Stays on

Sometimes, the check engine light isn’t one because there’s a problem with your engine; it’s one because there’s a problem with the circuit the light is attached to. A problem with your ECU can also result in issues with other electronic indicators on your dash; if the dashboard says one thing and the car itself says another, the problem is with the electronics.

Problems with the Battery

Sometimes, a bad ECU can cause your alternator to over or under charge your car battery. Try testing the same car battery in a different vehicle. If the problem doesn’t seem to be related to the battery itself, and isn’t caused by the batter cables, your alternator could be receiving bad instructions.

Bad Emissions Results

Because your ECU is connected to your engine, a problem with it can easily result in problems with you fuel efficiency. Make sure to check the emissions filter on your car, your oil levels, and the engine itself. If the parts all seem to be in working order, it’s time to check the ECU.

Unexplained Transmission Problems

If you have an automatic transmission, you rely on your ECU to shift gears correctly. When it goes out, you will notice grinding and clunking in the transmission. First make sure that you have transmission fluid, and that there aren’t any broken parts. If the ECU has been out long enough, the parts could be worn down from grinding against each other; replace the parts first, then check the electronic control unit.

You can usually check your ECU or ECM on your own using an on-board diagnostics tool. However, if the ECU is completely out, this tool won’t always work, and you will need to get a mechanic to take a look. In many cases, the ECU just needs to be repaired or reset, and the repair won’t be too expensive. Even if it has to be completely replaced, it’s well worth it; the electronic control unit is your car’s computer, and your car can’t run without it.