P0885
TCM Power Relay Control Circuit/Open
- Severity
- High
- Driving
- Drive only to a garage
A fault in the control circuit for the transmission module's power relay - an open circuit or a general fault, usually a broken wire, a bad connection or an open relay winding. This is the circuit the module uses to switch its own main power supply on. If the relay cannot be controlled, the module may lose power entirely or keep power when it should shut down, which drains the battery.
Possible causes
- CommonFailed power relay
- CommonCorroded relay socket or fuse box connections
- CommonWiring fault between the module and the relay
- PossibleWater ingress into the fuse box
- RareFailed control module driver
What you might notice
- Transmission in limp mode or completely dead
- Battery flat after standing
- Intermittent complete loss of transmission function
- Check engine light on
What to check, in order
- Swap the relay with an identical one elsewhere in the box and see whether the fault follows it. This is the quickest test available and costs nothing.
- Inspect the relay socket for corrosion, heat damage and spread terminals.
- Check the fuse box for water ingress, particularly if it is mounted low or in the engine bay.
- Check the wiring between the module and the relay.
- If the battery is going flat overnight, investigate this rather than dismissing it - a relay that will not release keeps the module awake.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Transmission
P0800P0801P0802P0803P0804P0805P0806P0807P0808P0809P0810P0811P0812P0813P0814P0815P0816P0817P0818P0819P0820P0821P0822P0823P0824P0825P0826P0827P0828P0829P0830P0831P0832P0833P0834P0835P0836P0837P0838P0839P0840P0841P0842P0843P0844P0845P0846P0847P0848P0849P0850P0851P0852P0853P0854P0855P0856P0857P0858P0859P0860P0861P0862P0863P0864P0865P0866P0867P0868P0869P0870P0871P0872P0873P0874P0875P0876P0877P0878P0879P0880P0881P0882P0883P0884P0885P0886P0887P0888P0889P0890P0891P0892P0893P0894P0895P0896P0897P0898P0899