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Home / Codes / P2138
DTC code page

P2138: Throttle/Pedal Position Sensor/Switch D/E Voltage Correlation

Quick answer: The paired accelerator-pedal signals disagree enough that the ECU no longer trusts driver-demand input.

Drivers also search this fault as accelerator pedal correlation code, APP sensor correlation fault, P2138 reduced power.

Severity: high Family: powertrain Related paths: 7
Meaning

What P2138 usually means

P2138 is one of the signature accelerator-pedal correlation codes. Unlike P2135, which often focuses on the relationship between throttle and pedal channels as a system, P2138 points more directly at the pedal-input side on many platforms. The ECU compares multiple pedal tracks for safety, and when D and E no longer agree closely enough, it usually drops the vehicle into reduced-power mode rather than guessing what the driver is asking for. This is high-intent search traffic because drivers often land here after a sudden limp-mode event with no obvious engine noise or misfire.

Fast triage

Start here before chasing parts

  • Scan first: save freeze-frame and pending codes before clearing anything.
  • Confirm the complaint: compare the stored code with current drivability symptoms.
  • Use context: trims, live data, and related codes usually narrow the fault faster than guesswork.
  • Work simplest to hardest: leaks, connectors, maintenance items, and known patterns before expensive components.
Initial checks

What to check first

  • Capture freeze-frame because P2138 often sets during a specific pedal movement or bump event.
  • Inspect the pedal connector and nearby harness routing, especially where feet, trim, or moisture can reach it.
  • Check whether the engine idles reasonably but will not respond normally to pedal input, which is a classic clue.
Driving risk

Can you keep driving?

P2138 often creates very limited throttle response, so driving should be kept to the minimum needed to reach a safe diagnostic location.

High urgency: If symptoms are active, reduce driving and diagnose quickly before secondary damage builds.
Symptoms

Common symptoms

Likely causes

Common causes behind this code

  • Accelerator-pedal position sensors disagree because one track is failing
  • Pedal connector or harness has corrosion, spread terminals, or intermittent open
  • Shared 5-volt reference or ground fault is skewing both pedal channels
  • Water intrusion or carpet-area harness damage is affecting the pedal circuit
  • An ECU-side circuit issue is distorting driver-demand input

Cause phrases often tied to this code: accelerator pedal sensor fault, pedal connector issue, 5 volt reference problem, wiring chafe, shared ground problem.

Diagnostic order

Suggested workflow

  1. Review APP tracks together and look for disagreement, dropout, or flat spots during a smooth pedal sweep.
  2. Inspect the pedal connector, terminal fit, and harness routing for intermittent faults.
  3. Verify reference voltage and ground stability at the pedal assembly.
  4. Check for companion throttle correlation codes to decide whether the fault stayed at the pedal or spread across the system.
  5. After repair, confirm full pedal response returns with no reduced-power event.
Avoid guesswork

Common mistakes

  • Replacing the throttle body when the fault lives in the pedal assembly or pedal wiring.
  • Ignoring moisture or carpet-area damage near the pedal connector.
  • Testing only for a dead sensor and missing an intermittent dropout.
Repair path

Practical fix guidance

  • Repair connector, reference, ground, or harness issues first because they are common and cheaper than module replacement.
  • Replace the pedal assembly when the APP tracks themselves are unstable or mismatched.
  • Retest on the road and verify the vehicle no longer falls into limp mode during pedal transitions.
Vehicle context

Affected brands in this MVP

Brand hubs help broaden internal linking now and can evolve into make-specific diagnostic notes later.

Aliases and common searches

English phrases tied to P2138

Useful when the driver knows the wording but not the exact DTC yet.

  • accelerator pedal correlation code
  • APP sensor correlation fault
  • P2138 reduced power
Related search intent

Queries this page can answer naturally

  • P2138 code meaning
  • what does P2138 mean
  • accelerator pedal position correlation code
  • P2138 limp mode
FAQ

Quick questions about P2138

Is P2138 more about the pedal than the throttle body?

Usually yes. It often points more directly to the accelerator-pedal sensor side of the system.

Why can the engine idle fine with P2138?

Because the ECU may still control idle but limit response when it stops trusting driver-demand input.

Can wiring near the pedal cause P2138?

Yes. Harness strain, moisture, and connector damage are common reasons.