P0703 means Brake Switch B Input Circuit. The computer is not seeing the expected signal from the brake switch input it uses for torque converter lockup, cruise control or shifting. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0703 means
Modern vehicles have many control modules that share information over a network, usually called the CAN bus. Codes starting with U mean a module has stopped hearing another one, and voltage and processor codes mean a module is not getting clean power or has an internal fault. Low battery voltage, poor grounds, blown fuses and damaged wiring cause many of these codes, so test the battery and charging system first.
P0703 symptoms
- Cruise control not working
- Torque converter lockup problems
- Brake lights not working on some vehicles
Common causes of P0703
- Faulty or misadjusted brake light switch
- Blown fuse
- Wiring or connector fault
How to diagnose P0703
- Check that the brake lights work
- Check the brake switch adjustment and connector
- Watch the brake switch input on a scan tool
Can you drive with P0703?
Yes, but check that the brake lights work for safety.
P0703 tips
A brake light switch that is slightly out of adjustment can cause lockup and cruise control problems; adjusting or replacing the switch is inexpensive.
Will P0703 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0703 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0740 | Torque Converter Clutch Circuit Malfunction |
| P0741 | Torque Converter Clutch Circuit Performance or Stuck Off |
| P0700 | Transmission Control System Malfunction |
Guides that help
When it is more than a sensor
Voltage and network codes come from wiring, the battery, the charging system or a module, not from engine or transmission wear. If a lost-communication code has left the transmission in limp mode, rule out the module and wiring before deciding the unit has failed, and see our transmissions only if testing confirms internal damage.
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