Powertrain, generic (extended)

P27B5 Internal Control Module Transmission Gear Ratio Control Performance

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

P27B5 sets when the supervision software doubts the ratio the transmission is running. Ford describes two triggers in its 2024 summary for the eight- and ten-speed automatics: protection against overspeeding a driveline element (UDS P0701_B1) and a plausibility test of the shaft speed ratio (P0701_64), both non-MIL; the 2020–2023 edition likewise keeps it without MIL on electronically shifted models. Detection takes less than a second. Ford TSB 20-2336 covers 2020 Super Duty trucks with the 6.7 L diesel built up to 19 August 2020, where P27B5 could come with a MIL, other codes and a forced idle; PCM reprogramming was the remedy. Genuine clutch slip or a speed sensor fault can create the same mismatch, so incorrect-ratio codes such as P0730 and sensor codes need checking too.

Likely causes

PCM/TCM software strategy (Ford TSB 20-2336)
Implausible input, intermediate or output shaft speed signal
Real slip of a clutch producing an unexpected ratio

Symptoms

  • Warning lamp or wrench light
  • Forced idle or torque reduction
  • Transmission held in a fixed gear

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€0–2,000
Time0.3–6 h

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

Parts involved

tcm

Related codes

P27B4P27B6P0730P0715P0720

References: fordservicecontent.com, fordservicecontent.com, static.nhtsa.gov.