P2138 Two accelerator pedal position sensor signals (D and E) that should agree with each other don't

Accelerator pedal position sensor D/E correlation

P2138 in short

P2138 means the two accelerator pedal sensors are reporting different pedal positions. Common causes are a poor connection at the pedal or a harness connector, damaged wiring and a worn pedal sensor. The car often goes into reduced power. If it suddenly loses power or drops to idle while driving, pull over safely and have it towed.

The accelerator pedal carries two (sometimes three) position sensors. They're designed to move together so the engine computer can check one against the other. 'D' and 'E' are usually the two pedal sensors.

If their signals stop matching, the computer can't be sure what you're asking for, so it sets P2138 and limits throttle. GM's bulletins describe an intermittent check engine light with 'Reduced Engine Power' and the code.

Most documented fixes are connections: GM repaired the instrument panel to body harness connector across many models, extended coverage for a pedal sensor connection on 2016-2018 Malibu, LaCrosse and Regal, and recalled 2014 ATS models for poorly crimped pedal terminals. Ford traced it to a junction box connector.

Most likely causes

  1. Poor connection at a harness connector between pedal and engine computer

    Supported by vehicle data
    Why it ranks here
    GM's long-running bulletin repairs the instrument panel to body connector for this code, and Ford and Suzuki bulletins also point to connectors.
    What would change this
    Likelier if the code is intermittent and the pedal itself tests good.

  2. Worn or faulty accelerator pedal sensor or its connection

    Common general cause
    Why it ranks here
    Worn pedal sensors are a common electronic throttle fault, and GM replaces the pedal assembly as necessary under special coverage.
    What would change this
    Likelier if one signal is erratic through the pedal travel with good wiring.
    How to test the accelerator pedal position sensor

  3. Damaged or poorly crimped pedal sensor wiring

    Common general cause
    Why it ranks here
    KBB lists damaged or corroded wiring first; GM's ATS recall was for poorly crimped pedal terminals.
    What would change this
    Likelier if wiggling the harness disturbs the signals.

  4. Engine computer software

    Possible — needs testing
    Why it ranks here
    KBB mentions computer software among the causes.
    What would change this
    Consider only after wiring and sensors test good.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read codes and watch both pedal sensor readings in live data while slowly pressing and releasing the pedal with the engine off

    Low riskTool: OBD-II scan tool with live data

  2. With the ignition off, look at the accelerator pedal sensor connector and the throttle body connector for corrosion, backed-out pins or harness rubbing

    Low riskTool: Flashlight

  3. Test the pedal sensor reference, ground and signal circuits, including terminal fit at inline connectors, to the service manual

    Best left to a shopTool: Digital multimeter, terminal test kit

    Warning:Back-probing or pin-fit testing can damage terminals; follow the maker's procedure.

Symptoms

  • Check engine light with a 'Reduced Engine Power' message
  • Sudden loss of power while cruising, or throttle response limited Gets more serious: stop and have it checked.
  • Engine drops to idle and won't respond to the pedal Gets more serious: stop and have it checked.

Compare with: Check engine light with loss of power

How to fix

  1. Ask a dealer whether your VIN is covered by an open bulletin or special coverage for the accelerator pedal or its wiring; GM, for example, extended coverage on some 2016-2018 Malibu, LaCrosse and Regal models.

  2. Write down when it happens (cold start, after rain or frost, at cruise, after a battery disconnect) and whether turning the engine off and on clears it. That detail helps the shop find an intermittent fault.

Parts and cost context

  • Accelerator pedal position sensor:The pedal sensors usually come as part of the pedal assembly. Check connectors and bulletins first; many P2138 repairs are harness connector fixes. Labour varies; get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Chevrolet

  • 2016–2018 · Malibu

    Supported by vehicle data

    GM special coverage for a pedal sensor connection that triggers reduced power with P2138. Whether the coverage is still current is not verified.

  • N182188250Status unverified

    Special coverage: accelerator pedal position sensor connection (Malibu, LaCrosse, Regal)

    2016–2018malibu · issued · NHTSA 10165443

    Special coverage: a pedal sensor connection can be interrupted, so the pedal still works but the car enters reduced engine power with P2138; the pedal assembly is replaced as necessary and harness repaired. Also 2017-2018 Buick LaCrosse and 2018 Regal.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • 07-06-04-019FStatus unverified

    Intermittent MIL, Reduced Engine Power and P2138: repair IP-to-body harness connector (revision F)

    2005–2018malibu, impala, equinox, silverado · issued · NHTSA 10139090

    Intermittent MIL with Reduced Engine Power and P2138; repair the instrument panel to body harness connector. Covers a wide range of GM models.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Buick

  • 2017–2018 · LaCrosse

    Supported by vehicle data

    Covered by the same GM pedal sensor special coverage. Whether the coverage is still current is not verified.

  • 2018 · Regal

    Supported by vehicle data

    Covered by the same GM pedal sensor special coverage. Whether the coverage is still current is not verified.

Cadillac

  • 2014 · ATS

    Supported by vehicle data

    Emission recall for poorly crimped pedal sensor terminals that can set P2138. Whether the recall work is still open on a given car is not verified.

  • 14176Status unverified

    Emission recall: APP sensor inline connector terminals, P2138 (Cadillac ATS)

    2014ats · issued · NHTSA 10093723

    Emission recall: pedal sensor terminals not properly crimped at an inline connector, which may set P2138.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Acura

  • IN-27-14Status unverified

    P2138 with poor engine performance (TL, TSX)

    2004–2008tl, tsx · issued · NHTSA 10055120

    MIL with P2138 and poor engine performance.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Ford

  • 2012–2013 · Focus

    Supported by vehicle data

    A junction box connector can set P2138. Whether the bulletin is still current is not verified.

  • ASI-44356Status unverified

    P2122/P2127/P2138 from a damaged or poorly seated battery junction box connector

    2012–2013focus, escape · issued · NHTSA 10055021

    Damaged or poorly seated battery junction box connector setting P2122, P2127 and/or P2138.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • P2135Two throttle or pedal position sensor signals (A and B) that should agree with each other don't

    Same system Possible — needs testing

    P2135 is the matching correlation code for the throttle position sensor pair.

  • P2122The signal from accelerator pedal position sensor D (usually the first pedal sensor) is lower than its normal range

    Shares causes Supported by vehicle data

    Ford lists P2122 and P2138 from the same poorly seated junction box connector.

All Electronic throttle and accelerator pedal codes

P2138 questions

My pedal still works but the car says Reduced Engine Power. Is that P2138?

It often is. GM describes exactly that: the pedal works but one sensor's connection drops out, so the computer limits power. Some 2016-2018 Malibu, LaCrosse and Regal models have extended coverage for it.

Can I drive with P2138?

Gently, to a shop, if power is only mildly reduced. If the car suddenly loses power or won't respond to the pedal in traffic, pull over safely and have it towed.

Sources and review

  1. p2138 Code - Throttle/Pedal Position Sensor/Switch 'D'/'E' Voltage Correlation — Kelley Blue Book (KBB Service Advisor)
  2. N182188250: Special coverage: accelerator pedal position sensor connection (Malibu, LaCrosse, Regal) — General Motors / NHTSA ,
  3. 07-06-04-019E: Intermittent MIL, Reduced Engine Power and P2138: repair IP-to-body harness connector — General Motors / NHTSA ,
  4. NHTSA recall 26V081: Electronic throttle body gears may break (2024-2025 Nissan Rogue 1.5L VC-Turbo) — Nissan North America / NHTSA ,
  5. NHTSA ODI Preliminary Evaluation PE13-003: Electronic throttle body malfunction (2009-2013 Escape, Fusion, Mariner, Milan) — National Highway Traffic Safety Administration, Office of Defects Investigation ,
  6. SB-01-045-10: P2104/P2111 with possible fail-safe speed limit (CX-9) — Mazda North American Operations / NHTSA ,
  7. ASI-44356: P2122/P2127/P2138 from a damaged or poorly seated battery junction box connector — Ford Motor Company / NHTSA ,
  8. TSB-23-06110: P2138 from connector or wiring between ECM and pedal sensor (Forenza, Reno) — American Suzuki Motor Corp. / NHTSA ,
  9. What You Should Know About Electronic Throttle Control — AA1Car (Larry Carley)
  10. 14176: Emission recall: APP sensor inline connector terminals, P2138 (Cadillac ATS) — General Motors / NHTSA ,
  11. p2135 Code - Throttle/Pedal Position Sensor/Switch 'A'/'B' Voltage Correlation — Kelley Blue Book (KBB Service Advisor)
  12. IN-27-14: P2138 with poor engine performance (TL, TSX) — American Honda Motor Co. / NHTSA ,
  13. 07-06-04-019F: Intermittent MIL, Reduced Engine Power and P2138: repair IP-to-body harness connector (revision F) — General Motors / NHTSA ,
Last reviewed
Written by
Saurabh K.
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