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
The Powertrain Control Module (PCM) supplies a 5-volt reference signal and a ground circuit to Throttle Position (TP) sensor, and a signal circuit to monitor changes in throttle angle. TP sensor signal voltage should be less than one volt at idle and 4.0 volts or greater at wide open throttle. DTC P0121 will set if PCM detects an out-of-range condition.
For duplication of DTC, ensure no active TP sensor or MAP sensor DTCs are present, engine is running, MAP sensor reading is less than 50 kPa or greater than 70 kPa, MAP is steady within 5 kPa, IAC position is 0-130 counts, and throttle angle is steady.
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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.
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