Code
P2138
Generic
P — Powertrain
Throttle/Pedal Position Sensor/Switch D/E Voltage Correlation
Views:
UK: 47
EN: 167
RU: 142
AI status
Completed
Completed
100%
Causes
- Damaged or corroded wiring or connectors in the sensor harness (open, short to ground, short to Vref)
- Intermittent or poor connector pin contact or contamination (moisture, corrosion)
- Faulty throttle position sensor(s) or accelerator pedal position sensor(s) (sensor D or E)
- Damaged insulation allowing sensors to short to each other or to another circuit
- Bad reference voltage (VREF) from the PCM or poor ground
- Throttle body mechanical problem or sticking linkage affecting sensor outputs
Symptoms
- Check Engine MIL on (DTC P2138 stored)
- Reduced engine power or limp mode
- Poor or erratic throttle response and hesitation
- Unexpected surging or idle problems
- Possible inability to accelerate normally
What to check
- Read and record freeze frame and freeze-frame parameters with a scan tool; note engine conditions when the code set
- Check for other related DTCs (other throttle/pedal or electrical codes)
- Visually inspect sensors, wiring harness, and connectors for damage, corrosion, or water intrusion
- Backprobe sensor connectors and monitor live sensor voltages while operating pedal/throttle
- Perform wiggle test on wiring and connectors while watching live data for intermittent changes
- Measure VREF and ground at the sensor connector with key ON (engine OFF)
Signal parameters
- VREF (reference) from PCM typically ~5.0 V (verify factory spec)
- Sensor D and E signal voltages normally range roughly 0.5–4.5 V across full travel (verify vehicle spec)
- Both sensor signals should track together smoothly as throttle/pedal is moved (proportional relationship)
- Expected correlation tolerance: signals should follow each other closely (typically within ~0.1–0.3 V across range; consult OEM spec)
- No abrupt jumps, dropouts, or mirror-image discrepancies in signal traces
Diagnostic algorithm
- Connect a capable scan tool and review freeze frame and live data for sensors D and E. Note values at rest and during pedal/throttle movement.
- Clear codes, perform a road or bench test to reproduce and capture live data while watching both sensor outputs.
- Visually inspect the sensor connectors, harness, and PCM connector for damage, corrosion, bent pins, or moisture.
- With key ON (engine OFF), backprobe each sensor signal and measure: VREF at connector, each signal voltage, and good ground. Compare to specs.
- Operate the pedal/throttle and confirm both sensor voltages change smoothly and correlate. Look for intermittent or nonmatching behavior.
- Check continuity from each sensor signal back to the PCM; check for shorts between the two signal wires and to VREF/ground using an ohmmeter (power off, connectors disconnected).
- If wiring checks good but one sensor shows incorrect or non-smooth output, replace the faulty sensor (D or E) and retest.
- If both sensors and wiring test good but code returns, inspect throttle body mechanics and perform throttle relearn/calibration per service procedure.
- If all wiring, sensors, and relearn procedures are correct and code persists, consider PCM diagnosis/replacement following OEM guidelines.
Likely causes
- Wiring harness damage or connector corrosion between sensor(s) and PCM
- One failed sensor (D or E) or intermittent sensor
- Contamination causing intermittent shorts between sensor signals
- Faulty VREF or ground circuit from the PCM
- PCM internal fault (least likely)
Fault status
Status
P2138 — Throttle/Pedal Position Sensor/Switch D/E Voltage Correlation. PCM detected inconsistent or non-correlated voltages between sensor D and sensor E.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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