DTC P0121: Throttle Position Sensor Circuit, Range/Performance Problem: Condition

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.