Throttle control codes wont clear, even though named parts replaced.
2009 Buick Lacrosse, 3.8 liter 6 cylinder
Approx 2 years ago, new MAF and Throttle body with TPS.
2 weeks ago the check engine light came on with "Reduced Engine Power".
Codes as follows:
P0068, Map, maf throttle position correlation,
P0102,Mass or Volume Air Flow A circuit low,
P1125, Accelerator Pedal Position System,
P2120, Throttle/ Pedal Position Sensor/ Switch D Circuit
P2138, Throttle/ Pedal Position Sensor/ Switch D/E Voltage Correlation
Since MAF and TB/sensor fairly new, I replaced the pedal.
Cleared codes. Last 3 came back (no MAF codes). Checked all connectors for
moisture and wire integrity. Did find some moisture in the multi connector (the
one mentioned in a service bulletin), dried it out and used electrolytic grease.
Tried to check voltage on TPS, but it has a 17 pin connector. Could not find a 5
volt input to the TPS. I found a 12 volt and a few under 5v (3.6v was strongest
under 5).
Cleaned up Throttle body and recalibrated TPS.
Cleared codes, they stayed off while i test drove (approx 3 miles) and same
codes returned with reduced engine power. Codes wont clear and R.E.P. light
stays on.
Live data indicates a discrepancy in my APPS voltages, but its a new pedal.
Ive tried to recalibrate the TPS again but it didnt change anything.
I cannot locate accurate info on the 17 pin connector.
At $200 for a new TB/TPS and new pedal installed, i dont want to spend it if its
not going to fix the problem.
How can i trace out this gremlin? Where might i locate good wiring info on these
sensors? How can i OHM out the sensors to determine if they are working?
Would a diag comp scan accurately locate it and could it differentiate between
bad sensors or /and ECU that needs to be replaced or reflashed.
Truth is that this is still a nice car and i couldnt replace it for the several hundred
this might cost. I dont mind spending the money, but i dont want to just
randomly swap out parts without knowing that its going to solve the issue.
Any help getting me in the right direction would be appreciated.
Dale