OBD-II Code · Sensors
P2138
Throttle/Pedal Position Sensor "D"/"E" Voltage Correlation
Severity
critical
Highest on our scale. Expect major repair cost if it is ignored.
Can you drive it
Not for long
Driving on this one risks further damage. Get it to a shop rather than carrying on with it.
Indicative cost (USD)
$200–$600
Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.
Pedal sensor D and E disagree by more than allowed.
How a shop works this
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.
Note every code that is set, not just this one.
Codes that appear together usually narrow the cause faster than any one of them read alone.
Read the freeze frame — the conditions the fault was recorded under.
Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.
Confirm the fault is current rather than history.
Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.
Then work the likely-causes list in the order shown.
That order is what a shop checks first for this code — wiring and connections before the component they run to, because a connector costs nothing to inspect and is a common answer.
If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.
Common symptoms
- Throttle limp
- Severe power loss
- Check engine light
Likely causes
- Failed pedal assemblyMost common
- Wiring
Read the full diagnostic procedureP2138 sets when the PCM sees the two redundant signals inside the accelerator pedal position (APP) sensor disagree outside the calibrated correlation…
P2138 sets when the PCM sees the two redundant signals inside the accelerator pedal position (APP) sensor disagree outside the calibrated correlation window, which is typically more than about 10 percent variance for longer than a half second. By design the ECU goes into reduced-power mode (often called limp home or forced idle) the instant this fault is active, because the throttle-by-wire system has no mechanical cable to fall back on.
Diagnose cheapest-first
- scan live data and watch APP1 and APP2 voltage sweep from idle to wide-open and look for a glitch, dropout, or non-linear step in either trace, then unplug the pedal connector and inspect for green corrosion, bent pins, or backed-out terminals (this alone resolves a huge percentage of cases).
- If both signals sweep cleanly at the pedal but the PCM still disagrees, back-probe the two signal wires at the PCM connector while flexing the harness to find a broken conductor.
- Caveat: replacing the pedal assembly without first inspecting the connector and harness is the single most common wasted parts purchase on this code, because the failure is downstream of the sensor maybe 60 percent of the time on trucks.
Vehicle-specific patterns2007-2013 GM full-size trucks and SUVs (Silverado, Sierra, Tahoe, Yukon, Suburban) with the 5.3L or 6.0L are the textbook case, where road salt and w…
- 2007-2013GM full-size trucks and SUVs (Silverado, Sierra, Tahoe, Yukon, Suburban) with the 5.3L or 6.0L are the textbook case, where road salt and water intrusion corrode the APP connector pins behind the kick panel and the fix is to cut the connector off, solder in new terminals, and seal with adhesive heat shrink.
- 2008-2012Ford Escape and Mercury Mariner suffer pedal sensor internal wiper failure that genuinely requires a new pedal assembly.
- 2006-2010Dodge Ram 1500 and 2500 commonly throw P2138 alongside P2122 or P2127 because of a chafed APP harness where it routes past the brake booster bracket.
- 2011-2015Chevy Cruze 1.4T sees pedal-internal failure plus PCM software updates from GM that recalibrate the correlation threshold.
Estimated repair$90 to $450.
Look up another code
P2138 — frequently asked
What does a P2138 code mean?
Pedal sensor D and E disagree by more than allowed.
What causes a P2138 code?
Common causes: Failed pedal assembly; Wiring.
What are the symptoms of a P2138 code?
Typical symptoms: Throttle limp; Severe power loss; Check engine light.
Is it safe to drive with a P2138 code?
Not for long. Driving on this one risks further damage. Get it to a shop rather than carrying on with it. Estimated repair: $200-$600.
How do I diagnose a P2138 code?
Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed. 1. Note every code that is set, not just this one. 2. Read the freeze frame — the conditions the fault was recorded under. 3. Confirm the fault is current rather than history. 4. Then work the likely-causes list in the order shown.
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