Symptoms of A Bad ECU: How To Tell If Your Car's Computer Is Failing?
Symptoms of A Bad ECU: How To Tell If Your Car's Computer Is Failing?

Are you experiencing problems with your car? If so, it’s possible that the ECU is to blame. In this post, we’ll discuss the symptoms of a bad ECU and how to tell if your computer is failing. We’ll also provide tips for repair

What Does An ECM Do?

What Does An ECM Do?

Your engine’s ECM makes constant, on-the-fly adjustments. Among its primary functions are managing the fuel-to-air ratio and engine timing. Also, it communicates with the PCM and TCM, which control the shifting, anti-lock brakes, and traction control.

It takes a lot of effort to manage all of these functions. Your ECM relies on dozens of sensors to get the information it needs to function effectively. Thus, ECM failure symptoms are actually caused by a broken sensor or faulty wire, not the ECM itself.

Symptoms of a Bad ECU

A faulty ECU can impact your car’s performance in a number of ways. Poor fuel economy is one of the most common symptoms of a bad ECU. If your car is suddenly getting less gas mileage than usual, it could be because the ECU is miscalculating how much fuel to inject into the engine. This can lead to wasteful fuel consumption and higher emissions levels.

Another symptom of a bad ECU is engine stalling. If your car stalls frequently, it could be because the ECU is failing to properly regulate ignition timing. This can cause the engine to misfire, which can lead to stalling. In some cases, engine failure may also occur as a result of a faulty ECU.

What is the Best Way to Diagnose ECM

An onboard diagnostic (OBD or OBD II) tool is the least invasive way to diagnose your ECM. From there, you can scan to see if your engine computers have produced any error codes. There are many of these codes, and your diagnostic tool’s manual should have information on what they mean.

We’ve written about some of these codes in the past. Here are a few of the most common:

P0600 Code: This code indicates that one of the sensors in your ECM is malfunctioning. Alternatively, it may just indicate a wiring error.

P0700: This code indicates a problem with your TCM. Although this is a different computer from the ECM, it can cause some similar symptoms.

P0606 Code: This code indicates a problem with your vehicle’s PCM. Again, this is only somewhat related to your ECM, but many of the symptoms are similar.

Frequently Asked Questions (FAQs)

If the ECU fails, what happens?
In automatic transmissions, a damaged ECU can cause problems shifting gears, or cause sudden jerking or stopping.

What are the signs that my ECU is working properly?
Typical examples include an engine failure light (MIL light) on the instrument cluster, an emergency mode on the car, a shaking car, or the engine no longer running on all cylinders. A malfunction of the engine control unit can cause all of these symptoms.

Also Read: Why Does My Car Overheat When AC is On?


If you’re experiencing any of these problems, it’s important to take your car to a mechanic and have the ECU checked. A bad ECU can seriously impact your car’s performance and may even cause irreparable damage if not fixed in a timely manner. Don’t hesitate to get your car checked out if you suspect that the ECU may be to blame.

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I'm David, and I love cars - especially writing about them! I'm the owner of, where I write car reviews and offer advice on car technical issues. My passion for cars started at a young age, when I would help my dad work on our family's vehicles. These days, I spend most of my time test-driving new models and researching the latest automotive technology. I'm always looking for a new challenge, so be sure to check out my website for the latest in car reviews and news. Thanks for reading!


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