Powertrain, generic · Transmission

P0891 TCM Power Relay Sense Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modeNo

Some gearboxes draw their power through a relay, such as the transmission control relay in Chrysler's fuse box that feeds the solenoids. P0885 to P0887 cover the coil control of that relay, P0888 to P0892 its sense line, which reads back the switched output and compares it with the command. A dead relay leaves all solenoids without power, so the gearbox drops into its hydraulic emergency gear. P0891 means voltage is present at the relay output although the relay is off: a stuck or welded contact or a back-feed. The module then cannot switch the solenoids off for a safe emergency gear, and it may stay powered after key-off and drain the battery. No maker documents the code.

Likely causes

Relay contact welded or sticking
Sense or output line shorted to voltage
Wrong relay fitted

Symptoms

  • MIL on
  • Battery drains overnight
  • Module stays awake after key-off

Repair estimate

DifficultyEasyDIY possible
Parts and labour€20–250
Time0.3–1.5 h

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

Parts involved

transmission relayrelay wiringfusetransmission control module

Related codes

P0888P0889P0890P0892P0887

References: law.cornell.edu, static.nhtsa.gov.