Powertrain, generic · Transmission

P0890 TCM Power Relay Sense Circuit Low

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

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. P0890 means the relay delivers no voltage despite the command. Subaru documents it in four bulletins from 2022 to 2025 (Ascent, WRX, Impreza, Crosstrek, Forester): after a short trip below 0 °C condensation freezes the ignition relay contacts, the starter does not crank and P0700 often comes along. Engine module software cycles the contacts; the 2025 Forester also gets a vented relay.

Likely causes

Relay contacts frozen or corroded (Subaru ignition relay)
Outdated engine module software (Subaru)
Fuse or wire between relay and gearbox module
Weak battery

Symptoms

  • Starter does not crank after a short trip in frost (Subaru)
  • MIL on, P0700 in the engine module
  • False oil level or other warnings

Repair estimate

DifficultyEasyWorkshop job
Parts and labour€30–300
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

P0888P0889P0891P0892P0882P0700

References: static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.