P0221Powertrain
Powertrain · SAE
TPS/Accelerator Pedal Sensor B — Range/Performance Fault
Meaning
The track B signal voltage of the TPS or accelerator pedal position sensor is within electrical limits but is implausible relative to track A or operating conditions. The ECU detects an incorrect correlation between the two redundant signals.
Common causes
- TPS/APP sensor with partially degraded track B
- High-resistance contacts at the connector on track B
- Wiring with intermittent resistance or partial chafing
- Interference on the signal B circuit
- Mechanical wear of the internal wiper contact
Symptoms
- Check-engine light (MIL) on
- Possible limp-home activation
- Non-linear or jerky throttle response
- Often accompanied by code P2138
- Anomalous behavior particularly at certain pedal positions
Severity
High: an implausible track B signal indicates the redundant system is unreliable; the ECU limits power for safety.
What to do
- Compare live TPS A and TPS B values with a scan tool: they must vary proportionally
- Measure TPS B sensor resistance at various pedal positions
- Inspect the connector for high-resistance contacts
- Check wiring for parasitic resistance
- Replace the TPS/APP sensor if the tracks are not correlated