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2000 GMC K3500 7.4L Engine P0122 TPS Code: No Signal to ECU - Diagnosis & Fixes

Model: TPS Fault Code: P0122 Posted: 2014-07-12 10:48

I own a 2000 GMC K3500 with the 7.4L engine, and it's currently displaying the P0122 throttle position sensor (TPS) fault code. I've confirmed that the TPS is receiving proper power (5V reference) and ground connections, yet no signal voltage is being detected from the sensor. After replacing the TPS module with a new one, the issue persists. What could be causing this? Any troubleshooting steps or diagnostic tips for this specific P0122 code on a 2000 K3500? Thanks in advance for any insights or advice.

Related fault codes
P0122
Comments (2)
Anonymous 2014-07-12 11:34

What does your OBD-II scanner show for the TPS signal voltage? Is it below 0.2 volts? Are there any additional diagnostic trouble codes (DTCs) present? Note: The scanner should detect all stored codes, including P1639. At the TPS connector, verify the wiring: - One wire provides a 5V reference voltage. - Another wire is grounded. What is the actual signal voltage on the sensor's signal wire? Is it around 0.2 volts? If possible, confirm the wire colors — though with only three wires, this setup is relatively straightforward.

Anonymous 2014-07-12 17:58

The throttle position sensor was registering a signal voltage under 0.25 volts for one second. Where exactly are you measuring the signal voltage? Are you backprobing at the TPS connector? If yes, it's possible that the signal wire is shorted to ground. To test this: 1. Disconnect the TPS connector. 2. Use small jumper wires (available at hardware stores like Radio Shack) to connect from the 5V reference terminal on the connector directly to the TPS signal terminal. 3. Also, connect a jumper from the ground terminal of the connector to the TPS ground. Then, connect your multimeter: positive probe to the TPS signal terminal and negative probe to the battery negative terminal. With the key ON, slowly open the throttle from fully closed to wide open. Observe if the voltage on the signal wire increases properly (should rise from 0V to near 5V). Additionally, inspect the connector and terminals by backprobing the signal wire while gently wiggling or stressing the connection — this can reveal intermittent faults.