What Does P2120 Mean?
The PCM has detected a circuit fault with accelerator pedal position sensor 'D' (typically the second redundant sensor). Modern vehicles use dual sensors for safety verification, and this code indicates an electrical problem with the secondary sensor circuit.
Safety Warning
Vehicle will enter fail-safe mode with limited or no throttle response. Engine may run at fixed RPM or refuse to accelerate. Not safe to drive; requires immediate attention.
Common Causes
40%
Faulty accelerator pedal position sensor assembly
30%
Damaged wiring or connector issues between pedal sensor and PCM
20%
Corroded or loose connector pins at pedal sensor or PCM
10%
PCM internal sensor circuit failure or power supply issue
Diagnostic Steps
1
Step 1: Inspect accelerator pedal position sensor connector for corrosion, damage, or loose pins; wiggle test connectors while monitoring live data
2
Step 2: Check sensor reference voltage and ground circuits at pedal sensor connector using a multimeter (typically 5V reference)
3
Step 3: Monitor sensor 'D' signal voltage while slowly depressing accelerator pedal; should sweep smoothly from approximately 0.5V to 4.5V
4
Step 4: Inspect wiring harness from pedal to PCM for damage, chafing, or pinched wires
5
Step 5: If all wiring and voltage checks pass, replace accelerator pedal position sensor assembly
Estimated Repair Cost
$150 - $600
Parts + labor, varies by vehicle and location
The PCM has detected a circuit fault with accelerator pedal position sensor 'D' (typically the second redundant sensor). Modern vehicles use dual sensors for safety verification, and this code indicates an electrical problem with the secondary sensor circuit.
The most common cause of P2120 (Throttle/Pedal Position Sensor/Switch "D" Circuit) is: Faulty accelerator pedal position sensor assembly
Typical repair costs for P2120 range from $150 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Vehicle will enter fail-safe mode with limited or no throttle response. Engine may run at fixed RPM or refuse to accelerate. Not safe to drive; requires immediate attention.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P2120 to identify the root cause.
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Quick Info
Category
Powertrain
System
Electronic Throttle Control
Difficulty
Type
Generic (SAE)
Recommended Tools
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