P2138 means Throttle/Pedal Position Sensor/Switch D/E Voltage Correlation. The accelerator pedal has two (sometimes three) position sensors that should agree. The computer has seen sensors D and E disagree. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P2138 means
Most vehicles built in the last two decades use electronic throttle control instead of a throttle cable: the accelerator pedal carries two or three position sensors, and the throttle body has a motor and two position sensors of its own. The computer compares the redundant sensors constantly, and any disagreement triggers reduced-power mode as a safety measure. Older engines with a throttle cable control idle with a separate idle air control valve.
P2138 symptoms
- Reduced-power mode
- Poor or no throttle response
- Idle only on some vehicles
Common causes of P2138
- Worn accelerator pedal position sensor
- Connector or wiring problems at the pedal
- Rarely, an engine computer fault
How to diagnose P2138
- Inspect the pedal connector
- Compare both pedal sensor readings while slowly pressing the pedal
- Check reference voltages and grounds
- Replace the pedal assembly if the sensors disagree with good wiring
Can you drive with P2138?
Limited; reduced power can be unsafe in traffic. Repair promptly.
P2138 tips
P2138 is about the accelerator pedal, not the throttle body. Pedal assemblies include their sensors, so a pedal that shows disagreeing sensor readings with good wiring is replaced as a unit.
Will P2138 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P2138 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P2135 | Throttle/Pedal Position Sensor/Switch A/B Voltage Correlation |
| P2101 | Throttle Actuator Control Motor Circuit Range/Performance |
| P0121 | Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance |
Guides that help
When it is more than a sensor
Throttle and idle codes are fixed at the throttle body, the pedal, a sensor or a leak. If those check out and the engine still runs poorly, a compression test separates a control problem from a worn engine; compare engines by code on our engines page.
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