Poor or corroded connection at the TCM power relay, its socket or the fuse holder; Low battery voltage or weak charging system, or a poor battery terminal or earth connection; Open circuit, high resistance or short to earth in the relay sense or supply wiring; Faulty TCM power relay with worn or burnt contacts; Blown or loose fuse feeding the relay or TCM; Water or damage in the transmission harness connector or internal wiring; Internal fault in the TCM or integrated mechatronic unit.

P0890

TCM Power Relay Sense Circuit Low.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
8: AreaTransmission
90: FaultThe specific fault in that area

What it means

P0890 means the transmission control module (TCM) has detected a low voltage on its power relay sense circuit. The TCM monitors the feed from the relay that powers it or its solenoids, and it set the code because the sensed voltage was lower than expected when the relay should have been energised. The exact relay arrangement and the thresholds used vary by model and transmission.

Symptoms

Transmission warning light or malfunction indicator lamp on
Transmission stuck in one gear (limp mode) or limited gear selection
Harsh, delayed or erratic gear changes
No shifting at all, or car will not move in some cases
Intermittent fault that comes and goes with vibration or damp conditions
Other transmission or network communication codes stored alongside

Possible causes

Poor or corroded connection at the TCM power relay, its socket or the fuse holderlikely
Low battery voltage or weak charging system, or a poor battery terminal or earth connectionlikely
Open circuit, high resistance or short to earth in the relay sense or supply wiringlikely
Faulty TCM power relay with worn or burnt contactspossible
Blown or loose fuse feeding the relay or TCMpossible
Water or damage in the transmission harness connector or internal wiringpossible
Internal fault in the TCM or integrated mechatronic unitrare

How to diagnose

Read all stored codes and freeze frame data, noting battery voltage, vehicle speed and whether other codes are present, then check for any relevant technical service information for the model.
Test the battery state of charge and the charging voltage with the engine running, and fix any low voltage issue before going further.
Inspect the relevant fuse and relay locations for looseness, heat damage, corrosion or water ingress.
Check the TCM and transmission connectors for corrosion, bent or pushed-back pins and damaged seals.
With a wiring diagram for the specific model, measure the supply, sense and earth circuits at the TCM for voltage drop, continuity and shorts.
Swap in a known good relay of the same specification or test the relay coil and contact resistance, if the design allows.
Carry out a voltage drop test on the power and earth feeds while the circuit is loaded and wiggle the harness to find intermittent faults.
Only if all wiring and supplies are proven good, consider TCM testing, following the manufacturer's procedure.

How to fix

Clean and secure corroded or loose relay, fuse and connector terminals, or replace damaged terminals and housings.
Repair or replace the battery, or fix the charging fault or poor earth connection causing low voltage.
Repair open, high resistance or shorted wiring in the relay sense or supply circuit.
Replace a faulty TCM power relay with one of the correct specification.
Replace a blown fuse only after finding out why it failed.
Repair or replace the TCM or transmission harness if damaged, and replace or reprogram the TCM only when it is confirmed faulty.

Can I keep driving?

Medium severity

The car may enter limp mode or lose gears without warning, so avoid long journeys and get it checked soon. If it will not shift properly or is stuck in gear, stop driving and have it recovered.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.