P2138 - Throttle/Pedal Position Sensor/Switch 'D'' / 'E' Voltage Correlation
System
Powertrain (Engine & Gearbox)
Technical Description
The control module has detected a fault in the Throttle/Pedal Position Sensor/Switch 'D'' / 'E' Voltage Correlation (P2138). Two sensors that should track together deviate beyond tolerance, forcing a fail-safe for safety.
Multimeter Test Points & Nominal Values
| Test Point / Component | Measurement | Nominal Target Range | Test Condition |
|---|---|---|---|
| Throttle/Pedal Position Sensor/Switch 'D'' / 'E' Voltage Correlation – Signal Voltage | Voltage (V) | 0.50 - 4.50 V (tracks operating range) | Ignition ON, connector engaged |
| 5 V Reference Voltage | Voltage (V) | 4.95 - 5.05 V | Ignition ON at sensor connector |
| Sensor Ground Voltage Drop | Voltage (V) | < 0.05 V (< 50 mV) | Under load to chassis ground |
| Signal Wire Continuity | Resistance (Ω) | < 0.5 Ω (Open = OL) | Disconnected harness between sensor and ECM |
Ignition ON, connector engaged
Ignition ON at sensor connector
Under load to chassis ground
Disconnected harness between sensor and ECM
Oscilloscope Waveform Analysis
100 ms/div, 1 V/divPossible Causes
Channel D:Verify dedicated wiring pins and signal pair for circuit D against the schematic.
Chafed or pinched wiring harness along the signal path to Throttle/Pedal Position Sensor/Switch 'D'' / 'E' Voltage Correlation
Poor ground connection or excessive voltage drop (> 0.1 V) at the ground point for Throttle/Pedal Position Sensor/Switch 'D'' / 'E' Voltage Correlation
Defective internal output driver or reference circuit in the control module for Throttle/Pedal Position Sensor/Switch 'D'' / 'E' Voltage Correlation
Symptoms
4
Recommended Solution
Compare signal voltage and resistance between circuit D and companion circuit A at module connector.
Graph both paired sensors simultaneously in scan-tool live data to pinpoint which sensor is diverging.
Verify loaded supply voltage and harness terminal pins at Throttle/Pedal Position Sensor/Switch 'D'' / 'E' Voltage Correlation.
Check circuit continuity and ground-side voltage drop (< 0.05 V) for Throttle/Pedal Position Sensor/Switch 'D'' / 'E' Voltage Correlation.
Unplug the sensor:the signal must swing to a known rail. Replace the sensor or repair the wiring based on the result.
Mechanic's Tip
Always run a loaded voltage-drop test on the sensor ground with ignition ON. A drop above 0.1 V shifts the whole signal and tricks the module into setting sensor codes on a good sensor.