P0802
Transmission Control System MIL Request Circuit/Open
- Severity
- Low
- Driving
- Drivable — book it in
A fault in the circuit the transmission module uses to request the check engine light - an open circuit or a general fault, usually a broken wire or a bad connection. This is about the request wire itself, not about the transmission. The practical consequence is that the transmission module may not be able to warn you: a genuine transmission fault could be stored without the light ever coming on.
Possible causes
- CommonWiring fault between the transmission module and the module that drives the lamp
- CommonCorroded or damaged connector at either module
- PossibleChafed harness shorting against the body or engine
- PossibleFailed instrument cluster lamp driver on vehicles wired that way
- RareFailed transmission control module output
What you might notice
- Check engine light on, or conversely never coming on when it should
- Warning lamp behaving inconsistently
- Usually no effect on how the car drives
What to check, in order
- Read the transmission module for its own stored codes. The point of this circuit is to warn you about those, so check what it was trying to report.
- Inspect the connectors at both ends of the circuit.
- Follow the wire looking for chafe damage.
- Confirm the warning lamp itself works at ignition-on bulb check.
- Treat this as a warning system fault rather than a transmission fault - but do not ignore it, because it means the car's ability to tell you about transmission problems is compromised.
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