P0221
Throttle/Pedal Position Sensor/Switch B Circuit Range/Performance
If your code reader dashboard displays the generic DTC error code P0221, your vehicle is currently experiencing an active failure related to "Throttle/Pedal Position Sensor/Switch B Circuit Range/Performance". Proper system troubleshooting is required to safely clear this warning.
Driver's Summary
A P0221 fault code points directly to a problem with throttle/pedal position sensor/switch b circuit range/performance that the ECM has confirmed over multiple drive cycles. Drivers typically experience erratic idle, surging, limited engine power when this code is active. This is a serious fault — avoid extended driving and have your vehicle inspected by a mechanic as soon as possible to prevent further damage.
Symptoms
Erratic idle, surging, limited engine power
Common Causes
- Worn internal tracks in TPS sensor
- Dirty throttle body
- Poor ground connection to TPS
- Failed accelerator pedal sensor
How to Fix
- 1 Replace TPS or throttle body
- 2 Clean throttle body
- 3 Clean ground connections
- 4 Replace pedal assembly
Technical Explanation
Detection of P0221 occurs when the ECM cross-references multiple sensor inputs and determines that the reported values are physically inconsistent or out-of-range. Misfire rate is counted per cylinder over rolling windows and compared against two thresholds: a catalyst-damaging rate (triggers flashing MIL) and an emissions-exceeding rate (triggers solid MIL). The PCM logs which cylinder is misfiring based on crankshaft position at the time of each detected event. The MIL illuminates after the fault is confirmed on two consecutive drive cycles, and the freeze frame data captured at first detection is stored in the PCM's memory for diagnostic reference.
Is It Safe to Drive?
An active P0221 code under high-severity conditions means the affected system is operating outside safe parameters. Continued driving — especially under load or at highway speeds — significantly increases the risk of secondary damage to components like dirty throttle body.
Mechanic's Pro Tip
The most common mistake with P0221 is replacing the sensor without verifying the reference voltage and ground integrity first. Use a scan tool to monitor the sensor's live output; a truly failed sensor shows a stuck, flatlined reading — a sensor that fluctuates but reads slightly off usually indicates a wiring or vacuum issue, not a dead sensor. Always spray electrical contact cleaner on the connector pins before condemning the sensor.
Cleaning: $50 - $100; TPS/Pedal replacement: $150 - $400