Powertrain, generic (extended)

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

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2138 is the standard plausibility check of a two-track accelerator pedal: D and E are pedal sensors 1 and 2 at GM, Ford and VW. GM's 2007 tables set it when the tracks differ by more than 10 % or their learned rest values by over 5 % (Type A); the 2023 table uses 0.12-0.18 V for 0.25 s in one trip. Ford flags more than 0.9 degrees and since 2020 lights MIL and wrench lamp; the 2014 VW Passat allows 0.17-0.70 V. GM bulletin 07-06-04-019F blames water entering the instrument panel to body harness connector, and special coverage N182188250 covers a pedal sensor connection on the Malibu (2016-2018), LaCrosse (2017-2018) and Regal (2018). Single-track faults have their own codes (P2122-P2128). The ECU reduces power.

Likely causes

Water or corrosion in a pedal or inline harness connector
Worn pedal sensor with one track drifting
Poorly crimped or loose terminals raising resistance
Aftermarket equipment tapped into pedal or 5 V reference circuits

Symptoms

  • Engine warning lamp with reduced engine power message
  • Sluggish, capped acceleration
  • Traction or stability control may be switched off on some models

Repair estimate

DifficultyEasyDIY possible
Parts and labour€20–400
Time0.3–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

accelerator pedal position sensorpedal sensor wiring

Related codes

P2122P2123P2127P2128P2139P2140

References: gsi.ext.gm.com, fordservicecontent.com, static.nhtsa.gov, static.nhtsa.gov.