Powertrain, generic (extended)

P2771 Four Wheel Drive (4WD) Low Switch Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

P2771 concerns the input that reports whether the transfer case sits in its low range. GM uses it on 2016 Silverado/Sierra with the MW7 gearbox as a plausibility test in the TCM: if the switch says high range while gear ratio math says low, or the reverse, for at least 0.5 s with fluid between 20 and 130 °C, the Type B code sets. The 2014 LML diesel ECM runs a similar comparison from turbine speed, output speed and ratio. GM's PIP4966B links P2771 on 2007–2011 trucks with Magna transfer cases to a speed-sensor tone wheel shifting on its shaft, or output shaft play, that corrupts the speed signal. Toyota's T-SB-0093-25 shows P2771 with subtype 11 (short to ground) on 2024–2025 Tacoma, fixed with a new shift actuator and breather hose. P2772–P2774 split the fault types.

Likely causes

Loose tone wheel or moving output shaft in the transfer case (GM PIP4966B)
Transfer case shift actuator damaged, e.g. by water through the breather (Toyota Tacoma)
Low-range switch or position encoder defective
Damaged wiring or corroded connector between switch and control module

Symptoms

  • Check engine light, often together with a flashing 4WD indicator
  • Erratic speedometer or ABS warning when a speed signal is affected
  • Low range not engaging, or transfer case disengaging under load

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–1,500
Time0.5–6.5 h

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

Parts involved

four wd low switchtransfer casewiring harness

Related codes

P2772P2773P2774P0836P279B

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