Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Circuit Description
Powertrain Control Module (PCM) supplies a 5-volt reference signal and a ground circuit to Throttle Position (TP) sensor, and monitors the TP signal circuit for changes in throttle angle. TP sensor signal voltage should be about.6 volt at idle and 4.5 volts or greater at wide open throttle. DTC P0121 will set if TP sensor angle is greater than a specified percentage at a given engine speed.
For duplication of DTC, ensure:
- Engine is operating on alternative fuel.
- No Alternative Fuel Electronic Control Unit (AFECU) DTCs are set (with the exception of DTCs P1215, P1432 and P1433).
- Engine MAP is less than 45 kPa.
- TP sensor angle has changed less than 2 percent in 2 seconds.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.