My 2007 Chevrolet Uplander is showing fault codes P2135 and P0121. I'm trying to determine whether the issue lies with the throttle position sensor (TPS) on the throttle body or the accelerator pedal position (APP) sensor on the gas pedal assembly. What should I check first? Are there any specific diagnostic steps for these codes in this model?
Yes, I have a scanner. It only shows P2135 and P0121 — no other codes are present.
Do you have a scan tool or just a code reader? You should check the freeze frame data and monitor TP sensor voltages. > TPS sensors (2) are located on the throttle body. > APP accelerator pedal position sensors (2) are typically mounted on the gas pedal assembly. Note: P0121 is not common for throttle actuator control (TAC) systems — more typical codes include P0120, P0122, or P0123. P2135 may relate to TAC operation. Confirming whether the code is actually P0121 is important before proceeding.
I replaced both the throttle position sensor (TPS) and the accelerator pedal position sensor, but the issue persists. What should I do next? Any further troubleshooting steps or possible causes?
Pkthomason — this is a one-year-old topic. It might be better to start a new post with updated details and clearer diagnostic context, especially since the issue may have evolved.
Start with code P0121 — are there any additional fault codes present? I suspect a missing signal, so check the 5V reference voltage at both terminals 1 and 2 on the TPS. Do you have access to a scanner with live data? This will help confirm sensor readings in real time.