Powertrain, generic (extended)

P27B6 Internal Control Module Transmission Speed Sensor Performance

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

P27B6 is the supervision check on the transmission speed signals. GM's 2024 heavy-duty TCM tables work out the output speed that should result from turbine speed and the current gear ratio and set the code, MIL on the first trip, when the raw output speed deviates by 10 or more for at least 10 seconds while output speed is at least 50, the range is not neutral and no shift is under way. Ford's summaries list it as non-MIL; the 2024 issue names tie-up protection (UDS P0701_92) and unintended deceleration (P0701_96) on its eight- and ten-speed automatics. Ford TSB 18-2211 dealt with a lit MIL and P27B6 on 2018 F-150 trucks with 2.7, 3.5 or 5.0 L engines built until 4 May 2018 by reprogramming the PCM. Pure sensor circuit faults carry P0715 or P0720.

Likely causes

Module software (Ford TSB 18-2211, PCM reprogramming)
Turbine or output speed sensor delivering an implausible signal
Damaged tone wheel or interference on sensor wiring

Symptoms

  • MIL or wrench light
  • Harsh or abrupt deceleration events
  • Fixed gear or limited shifting

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€0–1,200
Time0.3–4 h

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

Parts involved

tcmspeed sensors

Related codes

P27B4P27B5P0715P0720P0721

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