P2122

Code

Generic P — Powertrain

Throttle/Pedal Position Sensor/Switch D Circuit Low

Brand: Generic

Type: P — Powertrain

Views: UK: 33 EN: 104 RU: 76

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Page language: EN

Causes

Short to ground on the sensor D signal circuit
Open or high-resistance wiring or connector to the sensor
Failed throttle body position sensor or accelerator pedal position (APP) sensor (sensor D)
Poor or missing reference voltage (usually 5 V) or sensor ground
Intermittent connector contact or corrosion
Faulty ECM/PCM (rare)

Symptoms

Malfunction Indicator Lamp (MIL/Check Engine) ON
Reduced engine power / limp mode
Erratic or unresponsive throttle/pedal behavior
Poor idle, stalling, or hesitation under acceleration
Stored DTC(s) related to throttle/pedal position

What to check

Read freeze-frame and pending codes with a scan tool; note conditions when code set
Visual inspection of sensor, wiring harness, and connectors for damage or corrosion
Verify battery voltage is stable and ground connections at battery and engine are clean
Backprobe sensor connector to measure signal, reference and ground with key ON (engine OFF)
Wiggle test wiring and connectors while monitoring signal for intermittency
Check for aftermarket devices or recent repairs in the throttle/pedal area

Signal parameters

Reference voltage to sensor: typically 5.0 V (±0.25 V) with key ON
Sensor ground: near 0.0 V (solid chassis/PCM ground)
Sensor D signal low fault threshold: typically < ~0.5 V (varies by manufacturer)
Typical idle signal range (generic): ~0.5–2.0 V; wide open throttle: ~3.0–4.5 V
Expected signal behavior: smooth, monotonic increase with pedal/throttle movement (no sudden drops)

Diagnostic algorithm

Retrieve and record freeze-frame data and any related codes (P21xx family, P2135, etc.).
Visually inspect sensor(s), connectors and wiring for damage, pins pushed out, corrosion or signs of shorting.
With key ON (engine OFF) backprobe the sensor connector: confirm reference ~5 V, ground near 0 V, and measure the D signal voltage. If D signal is below expected (
Disconnect sensor and measure resistance (if applicable) or check for short to ground between the signal wire and chassis/ground using a multimeter. If short present, trace harness to repair.
Wiggle the harness and connector while monitoring the signal for intermittent faults. Repair damaged sections or replace connector as needed.
If wiring checks OK and sensor still reports low signal when connected, swap or bench-test the sensor per service manual or replace the sensor.
If replacing sensor does not clear the issue and wiring appears good, test PCM signal input pin and ground. If PCM input pin is shorted to ground, investigate PCM connector and harness; consider PCM replacement only after all wiring and sensor checks are complete.
Clear codes, perform a road/drive test and monitor live data to verify proper operation and that the P2122 does not return.

Likely causes

Damaged or chafed wiring to the sensor D signal wire (short to ground)
Contaminated or loose connector at the sensor or harness
Failed APP or throttle position sensor (internal short or degraded output)
Blown or poor ground/return at chassis or PCM
Aftermarket modifications or repairs that disturbed wiring

Fault status

⚠️ Status

Throttle/Pedal Position Sensor/Switch D Circuit Low. Low voltage detected on sensor D signal circuit; possible short to ground, sensor or wiring fault. May cause reduced power or limp-home mode.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours