P2138
Throttle/Pedal Pos Sensor/Switch D / E Voltage CorrelationP2138 is a generic OBD-II powertrain diagnostic trouble code: Throttle/Pedal Pos Sensor/Switch D / E Voltage Correlation. It is logged by the engine control unit when the throttle monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P2138 means
DTC P2138 is set when the Engine Control Module (ECM) detects that the voltage signals from two redundant throttle or accelerator pedal position (APP) sensors — designated circuits D and E — do not agree with each other. Modern drive-by-wire systems use at least two sensor tracks to provide a cross-check: typically one track outputs roughly half the voltage of the other across the pedal travel range, so the ECM can detect a single-point failure. When the correlation between the two signals falls outside the allowable tolerance window, P2138 is stored.
Because the throttle is safety-critical, the ECM responds immediately by entering a fail-safe (limp-home) mode that limits throttle opening to well below 50%, preventing unintended acceleration but also severely restricting performance. The check engine light illuminates and the vehicle may feel as though it has lost most of its power. In some implementations the PCM may also restrict cruise control and stability-control features until the fault is cleared.
The root cause is most often electrical rather than mechanical: corroded connector pins, chafed wiring in the sensor harness, or moisture ingress at the throttle body or pedal assembly connector account for the majority of confirmed cases. A true sensor failure — where one of the dual-track elements inside the TPS or APP sensor has worn out or shorted — is the next most common cause. In rare cases low battery voltage or a PCM calibration issue can cause intermittent disagreements.
Diagnosis should always begin with a thorough visual and electrical inspection of the wiring harness before condemning the sensor or throttle body, as connector cleaning and re-pinning frequently resolves the code at far lower cost than part replacement.
Common causes
Most-frequently reported root causes when P2138 is logged.
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1
Faulty accelerator pedal position (APP) sensor — one internal track failed or worn
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2
Corroded, damaged, or loose wiring in the throttle/pedal sensor harness
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3
Defective throttle position sensor (TPS) in the throttle body
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4
Damaged or contaminated throttle body affecting sensor readings
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5
Poor electrical connection at the sensor or ECM connector
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6
Low battery voltage causing loss of throttle body calibration
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7
PCM software requiring an update (rare)
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8
Water or debris ingress into the pedal or throttle body assembly
Symptoms drivers notice
How to diagnose P2138
A typical diagnostic flow when this code is present.
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1
Connect an OBD-II scan tool, record P2138 and all related codes, and capture freeze-frame data to understand operating conditions when the fault was set
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2
Inspect the throttle body, APP sensor, and all associated wiring harnesses for damage, corrosion, chafing, or loose connector pins; repair as needed before condemning parts
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3
Using a scan tool that supports live PID data, monitor APP sensor D and E voltages simultaneously across the full pedal sweep and verify they maintain the expected ratio
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4
Check battery voltage — a reading below 10 V during cranking can corrupt throttle body calibration; load-test the battery and charging system
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5
If wiring and voltage supply are good, perform a throttle body relearn/basic settings procedure with a factory-level scan tool
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6
Test the throttle position sensor signal voltages through the full throttle range; replace the throttle body assembly if one track is missing or erratic
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7
If the sensor and wiring check out, verify whether a PCM software update is available for the specific vehicle before replacing the module
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8
Clear codes, perform a road test, and re-scan to confirm the repair
Vehicles where we've handled P2138
Platforms in our catalogue with confirmed P2138 coverage.
Related powertrain codes
- P0120 — Throttle Position Sensor/Switch A Circuit Malfunction
- P0121 — Throttle Position Sensor/Switch A Circuit Range/Performance Problem
- P0122 — Throttle Position Sensor/Switch A Circuit Low Input
- P0123 — Throttle Position Sensor/Switch A Circuit High Input
- P0124 — Throttle Position Sensor/Switch A Circuit Intermittent
- P0220 — Throttle/Pedal Position Sensor/Switch B Circuit Malfunction
Frequently asked questions
Will P2138 leave me stranded?
Not usually — the vehicle enters limp-home mode, limiting throttle to roughly 20–50% to allow driving at reduced speed.
Can I clear P2138 myself and keep driving?
Clearing the code without fixing the underlying fault will cause it to return quickly.
Which vehicles most commonly set P2138?
Chevrolet (Malibu, Cobalt, Traverse), Nissan, Honda, Subaru, and Acura models appear frequently in repair data.
Is P2138 always a sensor failure, or could it be wiring?
Wiring and connector issues — corrosion, bent pins, chafed insulation — are actually the most common confirmed cause.
Do I need a special scan tool to fix P2138?
A basic OBD-II reader can retrieve the code, but diagnosing it accurately requires a scan tool that can display live dual-channel TPS/APP voltage data.
Disabling P2138 in software
RaceTune can permanently disable P2138 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
ECUs with a P2138 disable in our catalogue
Confirmed coverage from our recipe database — we support many more families. Upload your file and our identifier will match it automatically.
- Bosch EDC17C50 verified 1 software version
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
Got P2138 in your scan?
Upload your ECU file — we'll identify the exact software version and confirm whether a disable is available for your car.
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