What does it mean?
P1782 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Brake Pedal Signal Plausibility .
Symptoms
- MIL (check engine lamp) is on and the brake lights may stay on permanently or not work at all
- Cruise control refuses to engage or cancels immediately
- The shift interlock will not release, so the selector cannot be moved out of park
- Harsh feel as the torque converter clutch fails to release when braking
- Auto start-stop and similar functions are disabled
- Brake warning behaviour and lamp operation are inconsistent
Likely causes
- Brake light switch out of adjustment, so its two contacts do not change state together
- Failed dual-contact brake switch with worn or burnt internal contacts
- Crushed rubber pedal stop pad, which lets the switch plunger sit in the wrong position
- Corroded or loose connector at the pedal bracket, a damp area under the dash
- Open or shorted wire in one of the two brake switch circuits
- Aftermarket alarm, trailer module or dash camera tapped into the brake circuit
- Module input fault on one of the two brake signals
How to fix it
- Check brake lamp operation with the pedal released and pressed, including a light touch
- Watch both brake switch signals in live data while pressing the pedal very slowly, looking for one changing before the other
- Inspect and renew the rubber pedal stop pad, then adjust the switch to specification
- Inspect the connector and wiring at the pedal bracket for corrosion, damage and moisture
- Disconnect any aftermarket device wired into the brake circuit and retest
- Replace the brake switch, readjust it, and confirm both signals switch cleanly at the same pedal position