P0890: TCM Power Relay Sense Circuit Low

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.

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

Most 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• Outdated engine module software (Subaru)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

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the battery and grounds
2. With the connector unplugged, check whether the signal wire is making contact with ground.
3. Clear the code and see if it returns
4. If it is a reference voltage code, disconnect sensors one at a time and see if the voltage recovers
5. Check whether a software update is available
6. Do not replace the control module without a full diagnosis

Good to know

• Repair difficulty: easy
• It can trigger limp mode.
• It affects emissions.

What each character of P0890 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 8: Transmission
• 90: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0890?

It depends on the symptoms. If the car is running normally you can go to a repair shop; if it goes into limp mode, drive as little as possible.

What causes code P0890?

The most common causes are: relay contacts frozen or corroded (Subaru ignition relay); outdated engine module software (Subaru); fuse or wire between relay and gearbox module.

Related codes

• P0888TCM Power Relay Sense Circuit
• P0889TCM Power Relay Sense Circuit Range/Performance
• P0891TCM Power Relay Sense Circuit High
• P0892TCM Power Relay Sense Circuit Intermittent
• P0882TCM Power Input Signal Low
• P0700Transmission Control System (MIL Request)

Sources

• static.nhtsa.gov: MC 11005589 0001
• static.nhtsa.gov: MC 11016179 0001
• static.nhtsa.gov: MC 10215432 0001
• static.nhtsa.gov: MC 11014853 0001

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.