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 DTC P0120 Throttle Position (TP) sensor circuit diagnostic detects an out of range sensor signal. The TP sensor is a potentiometer whose resistance value changes along with throttle valve position. Powertrain Control Module (PCM) provides a 5-volt reference voltage to TP sensor. PCM reads voltage across TP sensor and uses voltage to calculate percentage of throttle valve opening. TP sensor resistance decreases as throttle valve opening increases. When TP sensor resistance decreases, voltage monitored by PCM increases. TP sensor resistance increases when throttle valve opening decreases, therefore, voltage monitored by PCM, will decrease. See TP SENSOR OPERATION table.
| Throttle Opening | TP Resistance | TP Percentage | TP Signal Voltage |
|---|---|---|---|
| Large | Low | High | High |
| Small | High | Low | Low |
NO RELATED
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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.