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Category: Chevy
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Experience:  ASE certified tech ADVANCED LEVEL SPECIALIST. Wisconsin certified emissions state inspector
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2000 SILVERADO/ 5.3L/ V8 / 4X4/ automaticdtc p0122..Check engine light

Resolved Question:

2000 SILVERADO/ 5.3L/ V8 / 4X4/ Automatic

DTC P0122.
Check engine light comes on intermittent with P0122. I have the ALLDATA P-Chart diagnostics for P0122 TPS CIRCUIT LOW VOLTAGE and full subscription to the service manual but I do not have a bi-directional scanner so I cant do the full test. However I tested the lines to the TPS as best as I could with a DMM and all 3 seem to be providing the proper voltages (ie, there is 5 volts on the grey wire, 12 volts on the black, and the blue wire is at 0.5 and goes smooth up and down to 4.5 when opening and closing the throttle). I have done these tests when the CEL is on, and when it has turned off. I cant seem to come to a definite conclusion as to if I have a failed TPS, or one of the wires is bad SOMEWHERE along the maze to the PCM. Also, I was at the dealer recently for an unrelated wiring repair (P0449) which was fixed at the cost of $400 and they also said I am throwing P1122. And, they also said I have a stored P0463 on the fuel level sensor circuit.
My question is two part:
1. In your opinion, with P0122 and P1122 issues does it sound like a wiring failure or failure of the TPS itself? I can easily install a new TPS, but heaven help me trying to trace wiring issues from the TPS since I cant tell where the lines go and the ALLDATA wiring diagram really doesnt help as far as showing me the routing of the wires in the engine compartment. And throwing money at a new TPS without proper diagnosis is just plain dumb, right? FYI..I do not notice any driveability issues when the CEL is on or off.

2. P0463- yes I have problems with my fuel gauge bouncing all over the place and often showing empty with the Message Center displaying LOW FUEL. I can get the fuel gauge to work again simply by shifting to 3rd or N when the vehicle is in motion. This issue is indeed annoying, but COULD the Fuel Level Sensor Circuit High Voltage (P0463) be related to P0122 or P1122??? I thought I saw in one of the electrical diagrams in ALLDATA that the TPS 5V reference and the Fuel Tank Pressure sensor are "related".
Submitted: 5 years ago.
Category: Chevy
Expert:  AMEDEE replied 5 years ago.

YES! It sounds like you have a bad TPS sensor. I would check the inputs (reference voltage and ground) going to the sensor before you replace it.

YES.. the P0463 could be related to the TPS sensor. Either the TPS is shorting out causing both of these codes, the fuel sending unit is bad causing both of these codes or you have an intermittent wiring issue causing both of these codes.
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