Avalon ECU error main relay

Hey, I'm having a weird issue with my 2021 Toyota Avalon with a gasoline engine. It's got 152546 km on it. Lately, I've been experiencing reduced engine power and the check engine light came on. Hooked it up to a diagnostics tool and it's showing an error stored in the error memory related to the ECU. Doing some digging suggests it might be the main relay causing the ECU to act up. Anyone else run into this before? Seems like ECU repair will cost around 120€.

4 comment(s)

That's quite a frustrating situation. I had a similar problem with my BMW 3 series a few years back. The symptoms you described mirror what I experienced. Reduced power and ECU error codes. In my case, a faulty sensor was causing the ECU to misbehave. Was there any specific error code registered in the error memory?

Thanks for the input. Yeah, the error code points specifically to the engine control unit being defective. I'm leaning towards the main relay being the culprit, but I'm not 100% sure. Did you initially suspect the ECU itself in your BMW, or did you focus on other components first?

I see. Given that the error code directly implicates the ECU being defective, and you suspect the main relay, I would recommend having the vehicle inspected by a qualified technician. Attempting to repair or replace the ECU yourself might introduce further complications. In my experience, it is always best to confirm the diagnosis before undertaking any repairs.

Appreciate the advice. I took it to a trusted independent shop. Turns out, a faulty main relay was indeed the cause. Replaced it, cleared the codes, and the car is running perfectly again. The final bill came to about 120€, just like I thought. Thanks again!

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