P0703
Brake Switch "B" Circuit
- Severity
- Medium
- Driving
- Drivable — book it in
A fault in the brake switch "B" circuit — the one the transmission module uses. The module needs to know when the brake pedal is pressed - to release the shift interlock, to disengage cruise control and the torque converter clutch, and to allow the car to be shifted out of park. A brake switch fault therefore shows itself in odd, seemingly unrelated ways.
Possible causes
- CommonMisadjusted or failed brake pedal switch
- CommonBroken or worn switch striker on the pedal bracket
- PossibleWiring or connector fault at the switch
- PossibleBlown brake light fuse
- PossibleAftermarket alarm or cruise control spliced into the brake switch circuit
What you might notice
- Cannot shift out of park
- Brake lights permanently on, or not working
- Cruise control will not engage
- Torque converter clutch not releasing on braking
- Check engine light on
What to check, in order
- Check whether the brake lights work, and whether they go off when the pedal is released. This one observation identifies most brake switch faults without any tools.
- Check the switch adjustment at the pedal. These switches are adjustable and go out of adjustment as the plastic striker wears.
- Watch the brake switch state on the live data screen while someone presses the pedal.
- Inspect the connector at the switch, which sits in the footwell where feet catch it.
- Ask whether an aftermarket alarm or cruise control was fitted - these are commonly spliced into this circuit.
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
P0700P0701P0702P0703P0704P0705P0706P0707P0708P0709P0710P0711P0712P0713P0714P0715P0716P0717P0718P0719P0720P0721P0722P0723P0724P0725P0726P0727P0728P0729P0730P0731P0732P0733P0734P0735P0736P0737P0738P0739P0740P0741P0742P0743P0744P0745P0746P0747P0748P0749P0750P0751P0752P0753P0754P0755P0756P0757P0758P0759P0760P0761P0762P0763P0764P0765P0766P0767P0768P0769P0770P0771P0772P0773P0774P0775P0776P0777P0778P0779P0780P0781P0782P0783P0784P0785P0786P0787P0788P0789P0790P0791P0792P0793P0794P0795P0796P0797P0798P0799