Code
P2121
Generic
P — Powertrain
Throttle/Pedal Position Sensor/Switch D Circuit Range/Performance
AI status
Completed
Completed
100%
Causes
- Faulty accelerator pedal position (APP) or throttle position sensor (TPS) D
- Damaged, corroded or loose connector at the sensor or ECM
- Open, shorted or high-resistance wiring in the signal, reference or ground circuits
- 5V reference or signal ground fault
- Mechanical binding in pedal assembly or throttle body linkage
- Contaminated or failed electronic throttle control (ETC) module/ECM
Symptoms
- Malfunction Indicator Lamp (MIL)/Check Engine Light ON
- Reduced engine power / limp mode
- Poor or delayed throttle response, hesitation or surging
- Unintended high or low idle in some cases
- Possible engine stall or inability to accelerate normally
What to check
- Read and record DTC(s) and freeze-frame data with a scan tool
- Check for other related codes (other APP/TPS or ETC codes)
- Visually inspect sensor connector and wiring for damage, corrosion, or pin push-out
- Backprobe and measure sensor signal, 5V reference and ground with a multimeter/scan tool
- Compare live sensor voltage/position data to other pedal/throttle sensors for correlation
- Wiggle harness and connector while observing live data for intermittent faults
Signal parameters
- 5 V reference present at sensor connector (typical)
- Signal voltage varies with pedal/throttle position and should be stable and linear
- Typical idle/rest signal approximately 0.5–1.5 V (varies by manufacturer)
- Typical wide open throttle signal approximately 3.5–4.5 V (varies by manufacturer)
- No sudden jumps, stuck values, or signals outside manufacturer-specified ranges — consult service manual for exact values and sensor output behavior
Diagnostic algorithm
- Connect a scan tool, read freeze-frame and live data. Note sensor D voltage/position and any related codes.
- Inspect the sensor connector and wiring harness for damage, corrosion, water intrusion, and secure fit.
- Verify 5V reference and ground at the sensor with ignition ON. If 5V or ground missing, trace back to ECM.
- With backprobe, measure sensor D signal at rest and while operating pedal/throttle. Confirm signal changes smoothly and stays within expected range.
- Compare sensor D output to the other APP/TPS channels (if present) to check for correlation or inverse relationship as specified by the vehicle.
- Wiggle test harness and connector while monitoring live data to find intermittent faults.
- If wiring, reference, and ground check good but signal abnormal, disconnect sensor and check for code change or substitution test with known-good sensor if available.
- Repair or replace damaged wiring, connector, or sensor as indicated by tests. Secure and protect harness from future damage.
- Clear codes, perform relearn/calibration procedures if required by the manufacturer, then road test and re-scan to confirm repair.
- If fault persists after sensor and wiring verified, consider ECM/ETC module fault and refer to manufacturer diagnostics or module testing procedures.
Likely causes
- Corroded/loose sensor connector or pin
- Broken or chafed wiring to the sensor (open or short to ground/power)
- Failed APP/TPS D sensor
- Poor ground or weak 5V reference from ECM
- Throttle body or pedal mechanical issue causing out-of-range signal
Fault status
Status
PCM detected that Throttle/Pedal Position Sensor/Switch D signal is outside expected range or inconsistent with other position sensors.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
Repair manuals
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Code
P2121
HUMMER
P — Powertrain
Accelerator Pedal Position (APP) Sensor 1 Performance
AI status
Completed
Completed
100%
Causes
- Faulty accelerator pedal position (APP) or throttle position sensor (TPS) D
- Damaged, corroded or loose connector at the sensor or ECM
- Open, shorted or high-resistance wiring in the signal, reference or ground circuits
- 5V reference or signal ground fault
- Mechanical binding in pedal assembly or throttle body linkage
- Contaminated or failed electronic throttle control (ETC) module/ECM
Symptoms
- Malfunction Indicator Lamp (MIL)/Check Engine Light ON
- Reduced engine power / limp mode
- Poor or delayed throttle response, hesitation or surging
- Unintended high or low idle in some cases
- Possible engine stall or inability to accelerate normally
What to check
- Read and record DTC(s) and freeze-frame data with a scan tool
- Check for other related codes (other APP/TPS or ETC codes)
- Visually inspect sensor connector and wiring for damage, corrosion, or pin push-out
- Backprobe and measure sensor signal, 5V reference and ground with a multimeter/scan tool
- Compare live sensor voltage/position data to other pedal/throttle sensors for correlation
- Wiggle harness and connector while observing live data for intermittent faults
Signal parameters
- 5 V reference present at sensor connector (typical)
- Signal voltage varies with pedal/throttle position and should be stable and linear
- Typical idle/rest signal approximately 0.5–1.5 V (varies by manufacturer)
- Typical wide open throttle signal approximately 3.5–4.5 V (varies by manufacturer)
- No sudden jumps, stuck values, or signals outside manufacturer-specified ranges — consult service manual for exact values and sensor output behavior
Diagnostic algorithm
- Connect a scan tool, read freeze-frame and live data. Note sensor D voltage/position and any related codes.
- Inspect the sensor connector and wiring harness for damage, corrosion, water intrusion, and secure fit.
- Verify 5V reference and ground at the sensor with ignition ON. If 5V or ground missing, trace back to ECM.
- With backprobe, measure sensor D signal at rest and while operating pedal/throttle. Confirm signal changes smoothly and stays within expected range.
- Compare sensor D output to the other APP/TPS channels (if present) to check for correlation or inverse relationship as specified by the vehicle.
- Wiggle test harness and connector while monitoring live data to find intermittent faults.
- If wiring, reference, and ground check good but signal abnormal, disconnect sensor and check for code change or substitution test with known-good sensor if available.
- Repair or replace damaged wiring, connector, or sensor as indicated by tests. Secure and protect harness from future damage.
- Clear codes, perform relearn/calibration procedures if required by the manufacturer, then road test and re-scan to confirm repair.
- If fault persists after sensor and wiring verified, consider ECM/ETC module fault and refer to manufacturer diagnostics or module testing procedures.
Likely causes
- Corroded/loose sensor connector or pin
- Broken or chafed wiring to the sensor (open or short to ground/power)
- Failed APP/TPS D sensor
- Poor ground or weak 5V reference from ECM
- Throttle body or pedal mechanical issue causing out-of-range signal
Fault status
Status
PCM detected that Throttle/Pedal Position Sensor/Switch D signal is outside expected range or inconsistent with other position sensors.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
Repair manuals
Manual library for HUMMER
138
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Code
P2121
MITSUBISHI
P — Powertrain
APS(main) range
AI status
Completed
Completed
100%
Causes
- Faulty accelerator pedal position (APP) or throttle position sensor (TPS) D
- Damaged, corroded or loose connector at the sensor or ECM
- Open, shorted or high-resistance wiring in the signal, reference or ground circuits
- 5V reference or signal ground fault
- Mechanical binding in pedal assembly or throttle body linkage
- Contaminated or failed electronic throttle control (ETC) module/ECM
Symptoms
- Malfunction Indicator Lamp (MIL)/Check Engine Light ON
- Reduced engine power / limp mode
- Poor or delayed throttle response, hesitation or surging
- Unintended high or low idle in some cases
- Possible engine stall or inability to accelerate normally
What to check
- Read and record DTC(s) and freeze-frame data with a scan tool
- Check for other related codes (other APP/TPS or ETC codes)
- Visually inspect sensor connector and wiring for damage, corrosion, or pin push-out
- Backprobe and measure sensor signal, 5V reference and ground with a multimeter/scan tool
- Compare live sensor voltage/position data to other pedal/throttle sensors for correlation
- Wiggle harness and connector while observing live data for intermittent faults
Signal parameters
- 5 V reference present at sensor connector (typical)
- Signal voltage varies with pedal/throttle position and should be stable and linear
- Typical idle/rest signal approximately 0.5–1.5 V (varies by manufacturer)
- Typical wide open throttle signal approximately 3.5–4.5 V (varies by manufacturer)
- No sudden jumps, stuck values, or signals outside manufacturer-specified ranges — consult service manual for exact values and sensor output behavior
Diagnostic algorithm
- Connect a scan tool, read freeze-frame and live data. Note sensor D voltage/position and any related codes.
- Inspect the sensor connector and wiring harness for damage, corrosion, water intrusion, and secure fit.
- Verify 5V reference and ground at the sensor with ignition ON. If 5V or ground missing, trace back to ECM.
- With backprobe, measure sensor D signal at rest and while operating pedal/throttle. Confirm signal changes smoothly and stays within expected range.
- Compare sensor D output to the other APP/TPS channels (if present) to check for correlation or inverse relationship as specified by the vehicle.
- Wiggle test harness and connector while monitoring live data to find intermittent faults.
- If wiring, reference, and ground check good but signal abnormal, disconnect sensor and check for code change or substitution test with known-good sensor if available.
- Repair or replace damaged wiring, connector, or sensor as indicated by tests. Secure and protect harness from future damage.
- Clear codes, perform relearn/calibration procedures if required by the manufacturer, then road test and re-scan to confirm repair.
- If fault persists after sensor and wiring verified, consider ECM/ETC module fault and refer to manufacturer diagnostics or module testing procedures.
Likely causes
- Corroded/loose sensor connector or pin
- Broken or chafed wiring to the sensor (open or short to ground/power)
- Failed APP/TPS D sensor
- Poor ground or weak 5V reference from ECM
- Throttle body or pedal mechanical issue causing out-of-range signal
Fault status
Status
PCM detected that Throttle/Pedal Position Sensor/Switch D signal is outside expected range or inconsistent with other position sensors.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
Repair manuals
Manual library for MITSUBISHI
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- SE Special Edition, AWD
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- SE Special Edition, FWD
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-
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- ES, AWD
- ES, AWD
- ES, FWD
- ES, FWD
- LE, AWD
- LE, AWD
- LE, FWD
- LE, FWD
- SE, AWD
- SE, AWD
- SE, FWD
- SE, FWD
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- SEL, AWD
- SEL, FWD
- SEL, FWD
- SEL Special Edition, AWD
- SEL Special Edition, AWD
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- SE Special Edition, AWD
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