alfredsky1

Viano engine power loss and ECU issues

My 2001 Mercedes Viano with a gasoline engine is giving me fits It's got 183355 km on the clock and recently the engine power has been cut in half I ran car diagnostics and it's showing a defective engine control unit I'm leaning towards a defective main relay causing ECU problems has anyone wrestled with this before I’m trying to avoid a huge ECU repair bill The computer module is throwing codes but I'm hoping it's not a full replacement situation

A 2001 Mercedes Viano experienced a significant engine power loss, with diagnostics indicating a defective engine control unit (ECU). The initial suspicion was a faulty main relay causing the ECU issues. After consulting a mechanic, it was confirmed that the main relay was indeed defective. Replacing the relay resolved the problem, avoiding the need for a costly ECU replacement.

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4 comment(s)

Whoa ECU problems are never fun I had something similar happen in my Vito though mine's a bit newer Reduced engine power and all that Did you check the simple stuff first like battery voltage Sometimes weird readings can mess with the engine control signals Also are you sure about the main relay being the culprit

Yeah battery voltage is solid I used my multimeter and it's reading a steady 12.6V when off and around 14.2V when the engine is running So I'm pretty confident that's not the issue You mentioned a similar problem on your Vito was it definitely the ECU and what was the fix I’m really trying to pin down the engine control issue before throwing money at ECU repair I also looked at the wiring harness but it seems fine

Okay good call on checking the voltage I just went to the mechanic In my case it turned out that a wire was loose But given your error codes point at the ECU maybe it’s really the ECU If you're seeing ECU errors in the diagnostics I'd say bite the bullet and get it checked by someone who knows their stuff A proper car diagnostics is the best thing you can do now

I appreciate the input I took your advice and went to a mechanic I trust Turns out you were right The main relay was defective They swapped it out cleared the error memory and now it's running like a champ again Total cost 120€ Not as bad as a full ECU replacement thankfully

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MERCEDES

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VIANOVITO