Throttle/Pedal Position Sensor/Switch D Circuit Low
The P2122 code means the vehicle's onboard diagnostic system has detected: Throttle/Pedal Position Sensor/Switch D Circuit Low. 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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Common Symptoms
- Severe reduced power mode
- Engine idle only with no acceleration
- Accelerator pedal feels disconnected
- Throttle warning light on
- Check engine light on
Probable Causes (Ranked by Likelihood)
- APP sensor D signal wire shorted to ground Very High
- Faulty APP sensor (internal short) High
- Corroded or water-damaged APP sensor connector Moderate
- Damaged wiring in APP sensor circuit Moderate
- Missing 5V reference voltage to APP sensor Low
Step-by-Step Diagnostic Procedure
-
Check APP sensor D voltage -- should be approximately 0.5-0.8V at rest, not near 0V
-
Inspect APP sensor connector for water intrusion, especially on floor-mounted pedals
-
Disconnect APP sensor and check signal wire for shorts to ground -- should read infinite resistance
-
Verify 5V reference voltage is present at the APP sensor connector
-
Replace APP sensor/pedal assembly if sensor is shorted internally
Frequently Asked Questions
Can I drive with code P2122?
No. The vehicle will be in severe limp mode and the accelerator pedal will not respond normally. The PCM sees a short-to-ground on the APP sensor D signal and disables throttle control for safety.
Can water damage the accelerator pedal sensor?
Yes. The APP sensor connector is located near the floor under the dash, making it vulnerable to water intrusion from leaking windshield seals, clogged AC drains, or wet footwell conditions. Moisture causes corrosion and short circuits in the connector.
Is this the same as the throttle position sensor on the throttle body?
No. The APP sensor (D and E circuits) is on the accelerator pedal. The throttle position sensor (TP) is on the throttle body. They are separate components. P2122 specifically refers to the pedal sensor, not the throttle body sensor.
Sources
This page is built from documented references. Verify against your own service info before repair work.
P2122 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:
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