Unsolvable MAP sensor/boost sensor g31 implausible signal

[SilverStargazin]

Hello all, thank you ahead of time for the help. Thank you to EvolutionArmory , Theiceman, and Nollywood for their help so far. Hoping to revive this fight and try to keep moving towards a solution to my car.

I can't figure out this g31 map sensor for the life of me and it's driving my crazy. I've searched for months and while I have found many threads with people having what looks to be the same problem as me, I haven't found a single thread with someone figuring it out. I have taken it to a foreign auto repair shop and they were no help. Here is the information and codes:

16621/P0237/000567 - Manifold Pressure / Boost Sensor (G31): Signal too Low

17026/P0642/001602 - Sensor Reference Voltage A: Circuit: Low

000566 Manifold Pressure/Boost sensor (g31), Implausible Signal

I've checked the wiring to the MAP sensor and i'm getting 5.6 volts with the key on. It's supposed to be 5v right? I've tried replacing the map sensor. I've tried a different ECU and still no avail. I know it's an electrical issue because when i clear the codes they automatically come back when i turn the key on again. I've checked the wiring to the MAP sensor and it looks okay and tests out okay. The car was driving great, then CEL came on and it wouldn't boost anymore. I then jacked it up, took a look at some more wiring, specifically around the diverter valve and n75 valve, could not find anything out of the ordinary. Noticed some zip ties were on the n75 wiring pretty tight, so i removed the zip tie and CEL was gone. Drove it for 30 minutes and it came back again, car stopped boosting. Numerous people think it's a wiring issue but I can't figure it out. I've checked the fuses for the ECM and they are good. Checked the fuses and relays in the ECU box and they look good. Tried new diverter valve and n75 valve for the hell of it, didn't change anything.

What should i do next? my map sensor is definitely getting power.

The wiring loom to the map sensor also has some wires that run underneath the car. Anyone know where those go to? What's up with the sensor circuit low? Could it be another sensor that isn't getting power?

SO grateful for anyone who reads and takes the time to try and help me. I dont have the money to take it to a specialist audi shop right now. Thank you thank you thank you for the comments and help.

-Lucus

[OliNix]

When I rebuilt my car I blew up a couple of MAP sensors... the plug is the same as the throttle... and both reach to each other. Do t know how your fault occurred but thought I would share this info incase it helps

[SilverStargazin]

I really appreciate the help. I will take a look to be sure but considering the CEL came and went without me touching anything in there, I suspect it's not the wrong wire. Someone suggested I chop the harness and replace the wiring. What do you think? Thanks

[texasboy21]

I really appreciate the help. I will take a look to be sure but considering the CEL came and went without me touching anything in there, I suspect it's not the wrong wire. Someone suggested I chop the harness and replace the wiring. What do you think? Thanks

That was me! The codes and symptoms to me sound like a wiring issue. Ross Tech’s wiki also suggestions wiring as a plausible cause.

http://wiki.ross-tech.com/wiki/index...6/P0642/001602

http://wiki.ross-tech.com/wiki/index...1/P0237/000567

[SilverStargazin]

That was me! The codes and symptoms to me sound like a wiring issue. Ross Tech’s wiki also suggestions wiring as a plausible cause.

http://wiki.ross-tech.com/wiki/index...6/P0642/001602

http://wiki.ross-tech.com/wiki/index...1/P0237/000567

lol thanks so much man! Found someone who is parting an a4 out and will be buying a harness and trying that. Hope it works.

[SilverStargazin]

Got some more information:

I retested the wiring harness for the MAP sensor and every wire is getting adequate power. The Ground is testing for continuity, the far wire gets 5.6V and the return wire is at 1v at idle. Here is what I did-

Unplug MAP harness - start car - test wires - while car was running, i plugged the map harness back in. The RPMS jumped up, then went back to idle. I checked the codes and the map sensor code went away. I was left with 2 codes, sensor circuit voltage low, low fuel pressure sporadic. Here is where it gets weird.

So i have 2 ECU's for the car. One is my bone stock ECU, other is SSP tuning stage 1. When i put my stock ECU in, i get all the same codes, but i also get a p1098 Intake Manifold Tuning Valve Position Sensor g336 Open or short to plus. When i change back to my SSP Stage 1 ECU I do not get thise code.

If the wiring is looking good. Maybe I should replace the intake valve sensor? I do not have a vag com so i cannot do the basic settings adapation. Not sure where to go from here.