What Does P2121 Mean?
The PCM has determined that accelerator pedal position sensor 'D' is reading values that are implausible or not correlating properly with sensor 'C'. This indicates a rationality or performance issue rather than a complete circuit failure.
Safety Warning
Vehicle will activate limp mode with reduced or unpredictable throttle response. May cause hesitation or unintended acceleration behavior. Vehicle should not be driven until repaired.
Common Causes
45%
Degraded or failing accelerator pedal position sensor with drift or inconsistent output
25%
Intermittent wiring connection or high resistance in sensor circuit
15%
Voltage supply issue affecting sensor reference voltage stability
10%
Mechanical binding or contamination affecting pedal position sensor reading
5%
PCM software calibration issue or internal processing fault
Diagnostic Steps
1
Step 1: Monitor both accelerator pedal position sensor signals (C and D) simultaneously using scan tool graphing function while slowly moving pedal
2
Step 2: Check for proper voltage correlation between sensor C and D; they should track proportionally but at different voltage ranges
3
Step 3: Inspect pedal assembly for binding, debris, or mechanical issues affecting smooth operation
4
Step 4: Measure reference voltage stability at sensor connector under load conditions; check ground circuit integrity
5
Step 5: Replace accelerator pedal position sensor if signals are erratic or do not correlate properly
Estimated Repair Cost
$150 - $600
Parts + labor, varies by vehicle and location
The PCM has determined that accelerator pedal position sensor 'D' is reading values that are implausible or not correlating properly with sensor 'C'. This indicates a rationality or performance issue rather than a complete circuit failure.
The most common cause of P2121 (Throttle/Pedal Position Sensor/Switch "D" Circuit Range/Performance) is: Degraded or failing accelerator pedal position sensor with drift or inconsistent output
Typical repair costs for P2121 range from $150 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle will activate limp mode with reduced or unpredictable throttle response. May cause hesitation or unintended acceleration behavior. Vehicle should not be driven until repaired.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P2121 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Powertrain
System
Electronic Throttle Control
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
