QPower95

A few days ago, my 90q threw a check engine light. The blink code yielded a 1231, the code for a vehicle speed sensor. I promptly replaced the sensor but the check engine light continues to come on. I even did a hard reset and disconnected the battery for two hours. That made the light go away for the day, but it came back on later that night. The speedometer and instruments are all functioning correctly

Last night, I noticed that my cruise control no longer works. When I try to turn it on the cel comes on immediately. Idk what's going on or how to fix it. Cruise malfunctioning? Bad ECU? Still a bad VSS?

If anybody has any advice OR a wiring diagram please help!

Loudgoldwing

(I'm out of town right now, no access to codes)

Possibly an issue with the ENGINE speed sensor?

If not, you have a corroded/broken area of the wiring from the wheel sensor up.

QPower95

the engine speed sensor throws a different code

2111 - engine speed sensor
1231 - vehicle speed sensor

I also thought this at first, but i tested the engine speed sensor and found it to be functioning correctly.

QPower95

just a thought, but could this be a symptom of the infamous trunk wiring harness? I just checked mine and almost all of the wires are broken, and all of them are uncovered. I think I remembered reading somewhere that the trunk harness fights into the cluster somehow...

Lago Blue

You may be correct in that a CEL can be:
- something out of range for long enough that the fault is sensed by the ECM;
- a flag to get you to check that whole particular branch right back to and including the ECM connection, and not necessarily the just the end sensor itself; &
- often an indication of an entirely different issue elsewhere.

See posts #4 & #6 here re possible connection between trunk wiring fault and cruise function:

https://www.audiworld.com/forums/sho...+wiring+cruise

QPower95

I repaired my trunk harness and besides getting my reverse lights back, nothing happened. All of my lights are working. All of my fuses are intact. My cruise still won't work and the light is still coming on. Next i'm gonna check and clean the wiring directly to the VSS and check the cruise system. This is getting frustrating.

QPower95

cleaned the plugs for the vss and another sensor on the same branch. Took apart the vss and cleaned it as well. I coated the plugs with dielectric grease and reconnected them. This seems to have helped, but the cruise control still doesn't function and it still turns on the light if I try to use it. Could a bad cruise pump cause the CEL?

QPower95

in addition to the cruise not functioning, If I lock the diff it STAYS LOCKED. it does not automatically shut of a 15 mph. Could the diff cause the cell? or anything near the diff servo?

CRAZY_RUSSIAN

try your wheel speed sensors

QPower95

do you know if there is a way to test them?