Open circuit, chafed or broken wiring in the TCM power relay control circuit; Corroded, loose or pushed-out pins at the relay, relay socket or TCM connector; Faulty TCM power relay with an open coil; Blown fuse or poor power or earth supply to the relay circuit; Fault in the driving module (TCM, engine control unit or body control module, depending on the model) with a failed relay driver; Water ingress or damage to the wiring harness, for example near the transmission or underbody connectors.

P0885

TCM Power Relay Control Circuit/Open.

Generic
Powertrain
Generic code
Medium severity

How this code is built

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

What it means

P0885 is the generic code for an open circuit in the control circuit of the transmission control module (TCM) power relay. The TCM, or the module that drives the relay, commands the relay on or off and monitors the circuit. It sets the code when the voltage it sees on the control circuit does not match the commanded state, which points to an open circuit.

Symptoms

Transmission warning light or malfunction indicator lamp on
Transmission stuck in one gear (limp mode) or in neutral
Harsh, delayed or no gear changes
No shifting at all or loss of drive
Gear selector position not shown correctly on the dash
Intermittent fault that comes and goes with vibration or temperature

Possible causes

Open circuit, chafed or broken wiring in the TCM power relay control circuitlikely
Corroded, loose or pushed-out pins at the relay, relay socket or TCM connectorlikely
Faulty TCM power relay with an open coillikely
Blown fuse or poor power or earth supply to the relay circuitpossible
Fault in the driving module (TCM, engine control unit or body control module, depending on the model) with a failed relay driverpossible
Water ingress or damage to the wiring harness, for example near the transmission or underbody connectorsrare

How to diagnose

Read all stored and pending codes and the freeze frame data, noting whether the fault is current or intermittent, and check for related codes such as low voltage or communication faults
Check the battery condition and charging voltage, as low voltage can cause related faults
Find the TCM power relay and its fuses using the wiring diagram for the specific model, as the location and layout vary, and inspect the fuses
Inspect the relay, socket, TCM connector and harness for corrosion, water, heat damage, chafing and loose pins
Wiggle test the harness with the system monitored to see if the fault appears or clears
Test the relay coil resistance and swap in a known good identical relay if the design allows
With the ignition on, check for supply, earth and control signal at the relay socket and carry out continuity checks on the control wire back to the module, following the wiring diagram
If the wiring and relay prove good, check the driving module output and consider a module fault, confirming any software updates for the model

How to fix

Repair or replace damaged wiring and restore the open circuit with proper soldered or sealed joints
Clean or replace corroded connectors and terminals and refit any loose pins
Replace the faulty TCM power relay with the correct specification
Replace any blown fuse after finding and fixing the cause of the overload
Repair or replace the control module only after the wiring and relay are proven good, and apply any manufacturer calibration update if an outdated one is a known cause for that model

Can I keep driving?

Medium severity

The car may go into limp mode or lose drive without warning, so avoid it except for a short trip to get it repaired. Fix it soon, as a loss of gear changes can be unsafe in traffic.

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