Throttle/Pedal Position Sensor/Switch D Circuit
The P2120 code means the vehicle's onboard diagnostic system has detected: Throttle/Pedal Position Sensor/Switch D Circuit. This is a critical severity code.
- Keep driving?
- No — stop driving
- DIY difficulty
- moderate
- Estimated cost
- $100 - $400 (parts and labor)
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What Are the Symptoms of P2120?
- Severe reduced power or limp mode
- Accelerator pedal unresponsive
- Engine stuck at idle
- Multiple throttle warning lights
- Check engine light on
What Causes P2120? (Most Likely First)
- Faulty accelerator pedal position (APP) sensor Very High
- Damaged or corroded APP sensor wiring or connector High
- Open circuit in APP sensor D circuit Moderate
- APP sensor connector water intrusion Moderate
- PCM input circuit failure Low
Can I Still Drive with P2120?
No — stop driving. P2120 is rated critical severity. Continuing to drive in this state risks further damage — get it looked at before your next trip.
Frequently Asked Questions
Can I drive with code P2120?
No. The vehicle will be in severe limp mode or the accelerator pedal may not respond at all. The PCM relies on the APP sensor to know how much throttle you want, and without a valid signal, it cannot safely control the throttle.
What is the accelerator pedal position sensor?
The APP sensor is built into the accelerator pedal assembly. It converts pedal position into electrical signals that the PCM uses to control the electronic throttle body. Most have two independent signal tracks (D and E) for safety redundancy.
Can I just replace the sensor or do I need the whole pedal?
On most vehicles, the APP sensor is integrated into the pedal assembly and must be replaced as a complete unit. Some vehicles have a separate sensor that bolts onto the pedal bracket. Check your specific vehicle for availability.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose P2120?
-
Monitor APP sensor D signal with scan tool -- should change smoothly from 0.5V to 4.5V as pedal is pressed
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Inspect APP sensor connector at the accelerator pedal for corrosion or moisture
-
Check for 5V reference voltage and ground at the APP sensor connector
-
Wiggle APP sensor connector while monitoring signal -- look for dropouts indicating intermittent contact
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If wiring tests good, replace the accelerator pedal position sensor assembly
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
P2120 on Diesel, EV & Equipment
The same code ID appears across other engines and platforms. The diagnostic flow varies by manufacturer — these are the platform-specific breakdowns:
Which Vehicles Commonly Get P2120?
- 2007-2017 Chevrolet Silverado
- 2008-2016 Dodge Charger
- 2009-2018 Ford F-150
- 2006-2015 Nissan Altima
- 2010-2019 Toyota Camry
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