P0857
Traction Control Input Signal Range/Performance
- Severity
- Medium
- Driving
- Drivable — book it in
The traction control input signal is present but implausible - it does not agree with what the transmission module knows from its own speed sensors. One of the two sources is wrong, and the module cannot tell which.
Possible causes
- CommonWheel speed sensor fault upstream
- CommonMismatched tyre sizes or a space-saver spare fitted
- PossibleFault in the ABS or traction control module
- PossibleTransmission output speed sensor fault
- PossibleNon-standard wheel or tyre sizes changing the calculation
What you might notice
- Traction control warning light on
- Traction control activating when it should not
- Transmission shifting oddly under acceleration
- ABS warning light on as well
What to check, in order
- Check the tyres. A space-saver spare, mismatched sizes or badly uneven wear makes wheel speeds genuinely disagree, and that is a far more common cause than any electrical fault.
- Read the ABS module for wheel speed sensor codes.
- Compare the individual wheel speeds on the live data screen while driving straight on a level road - they should be close to identical.
- Check the transmission output speed sensor reading against road speed.
- Ask whether non-standard wheels or tyres have been fitted.
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