Hello all, Not sure where to post since this started as a tuning ECUFlash issue, then it could be an engine issue, or now a wiring issue.

I am still working on a tricky and somewhat frustrating 02 sensor CEL. The details are HERE. More than you probably want to read, so the jist is I get code P0031, I replaced the front 02 sensor, the wire and connector for the sensor, the battery, did the rear 02 sim patch, and none worked.

So now I am trying to chase any wiring to test for appropriate continuity from the ECU to the sensor(s). This is kind of a goose chase but provides a good learning opportunity. However I need help.

I have searched for an 9MR wiring schematic, but can only come up with evo8s. ? If I am being search moronic can someone point me to that doc.

Also if anyone knows what wires in total are used for the 02 sensors and their route from the ECU to the sensor so i can test them all for damage that would be a big help.

Below I have pics of the issue that started me looking at wire damage. The White wire from the ECU is labeled in pinout diagrams as the Lambda wire. I don't know what exactly for the 02 sensor it does, but that white wire on my car goes into this large Green sleeve. I first thought it was a repair, but unravling the harness shows that this Green think thing continues. Is that so on other cars (likely not since there is bare wire hanging out!!!)

Any help or ideas greatly appreciated.

 

all of them like that are factory..., maybe shielding..i dunno but i know they are fine like that.

 

Hey Mike. Did you get the 02 nightmare sorted out? Sorry I haven't replied. I *JUST* got your visitor message dated March 28. I didn't even know there was such a thing as 'visitor message' on my profile page lol, so when I read yours, I was thinking 'what the hell is this?'. So sorry, let me know if I can be of any help.

 

jb.
Yup I got it figured out after lots of goofy tests. It is a broken wire in the loop between the ECU and the front 02 sensor, however the break is somewhere just inside the firewall by the harness near the MB cylinder. I didn't want to open the loom for that repair, so I ran a jumper (a single wire) from the EDU directly/independently to the 02 sensor plug in the valve cover. Once that was in place everything worked as it should.
Thanks for the follow up.
Wiring gremlins are a PITA!
M