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.
Code 21 - TPS Open Or MISADJUSTED
The Throttle Position Sensor (TPS) is a variable resistor that supplies the ECM with throttle opening information. The sensor is supplied with a 5-volt reference signal. Sensor resistance is lowest (high signal to ECM) at wide open throttle.
Code 21 means that the ECM has seen high voltage at terminal "A2" for more than 30 seconds with engine speed below 1120 RPM.
- Checks to confirm if Code is still present.
- Checks reference voltage at TPS harness connector to determine whether problem is in electrical circuit or TPS.
- Checks to see if low reference voltage is due to a grounded wire or ECM.
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.