MoTeC Global Forum

I'm on a college FSAE team and we're having an unusual issue with our M400 ecu. We actually have two identical ECUs. During assembly of our car this year, we had some electrical issues. Some shorts and blown fuses, etc. After trying to start, we found that our sensor ground(B16) is at 5v instead of 0. We checked for shorts in the harness but couldn't find anything. So we tried our other ECU running an identical config(literally just copy pasted), and sure enough, it's 0v at B16. We reflashed both ECUs, and nothing changed. It seems like there might be an internal problem shorting B16 to a 5v supply. Has anyone ever experienced anything like this? Any common issues we should be aware of? Thanks in advance! -Ivan

It is from the internal ground link being blown. Too much current has passed through the ground and blown the internal fuse link. They run a fuse link from the sensor/aux etc grounds to the main ground inside the case. This stops bigger problems from over-current killing the board.

I have done this from passing too much ground current from my ignition coils through the sensor ground.

Check on the mainboard if the pads soldered in the picture i’ve attached are blown.

You should not solder bridges across the pads.
Doing so may permanently damage the ECU if you have a short to +12V.

I know...this is how i got the ecu in the shop...

At a minimum, put a PTC fuse there.