DTC P0121: Throttle Position Sensor Circuit, Range/Performance Problem: Condition
WARNING: This page is about a different car, the 2002 Mazda Protege5 and 2002 Mazda Protege. However, it is still accessible from the selected car via links, so may be relevant.
If PCM detects throttle valve opening angle is less than 12.5 percent for 5 seconds after engine coolant temperature is more than 158°F (70°C) and Mass Airflow (MAF) sensor signal is more than 73.4 grams/sec., PCM determines throttle valve is stuck closed. If PCM detects throttle valve opening angle is more than 50 percent for 5 seconds after engine RPM is more than 500 RPM and MAF signal is less than 5 grams/sec. PCM determines throttle valve is stuck open. This is a continuous monitor. MIL is illuminated when PCM detects malfunction during 2 consecutive drive cycles. Possible causes are:
- MAF sensor malfunction.
- PCM malfunction.
- Poor connection in Throttle Position (TP) sensor signal circuit.
- TP sensor malfunction.
- Voltage drops in reference voltage supply circuit or ground circuit.