P081F
Brake Transmission Shift Interlock (BTSI) Signal Correlation.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 8
- AreaTransmission
- 1F
- FaultThe specific fault in that area
What it means
P081F means the control unit has found that the signals used by the brake transmission shift interlock (BTSI) do not agree with each other. This is typically the brake pedal position or brake switch signal compared with the shift interlock command, the shift lock state or the selector position. The exact signals compared vary by model and transmission type, so check the manufacturer's data for the vehicle.
Symptoms
- Gear selector stuck in Park, or will not move out of Park with the brake pressed
- Selector moves out of Park without the brake pedal pressed
- Brake lights not working, or staying on
- Engine will not start or crank, or starting is inconsistent, on models where start permission depends on the brake or range signal
- Gear indicator on the dash is wrong or flickers
- Warning light on, and possibly a transmission warning message
Possible causes
- Faulty or misadjusted brake light switch or brake pedal position sensor giving a wrong or intermittent signallikely
- Faulty shift interlock solenoid or selector assembly, or a sticking mechanismlikely
- Wiring faults such as chafing, corrosion, high resistance or a loose connector in the brake switch or interlock circuitpossible
- Blown fuse or low supply voltage to the brake switch or interlock circuitpossible
- Fault in the transmission range sensor or selector position signal that does not match the interlock statepossible
- Control unit fault or outdated software, where the manufacturer lists it as a known causerare
How to diagnose
- Read all stored and pending codes and the freeze frame data, and note any related brake, body control or transmission codes
- Check that the brake lights work and come on and go off correctly when the pedal is pressed and released
- Inspect the brake switch or pedal sensor, its mounting and adjustment, and its connector for damage, moisture or corrosion
- Check the relevant fuses and the battery condition and charging voltage, as low voltage can cause false signal faults
- Using a scan tool's live data, compare the brake pedal signal with the interlock command and the selector position while pressing the pedal and moving the selector
- Test the shift interlock solenoid for correct operation and check its supply, earth and signal wiring against the manufacturer's wiring diagram
- Check the selector mechanism and range sensor for wear, a loose fit or incorrect adjustment, following the procedure for that model
- Check for software updates or technical bulletins for the model before replacing any control unit
How to fix
- Replace or correctly adjust the brake light switch or brake pedal position sensor
- Repair damaged wiring or connectors, or replace corroded terminals in the affected circuit
- Replace the shift interlock solenoid or selector assembly if it is faulty or sticking
- Replace a blown fuse once the cause of the failure has been found, and correct any battery or charging problem
- Adjust or replace the transmission range sensor if its signal is incorrect
- Update the control unit software if a known fault or an outdated calibration is confirmed, or replace the unit only after other causes are ruled out
Can I keep driving?
The car can usually be driven if it starts and selects gears normally, but have it checked soon. Faulty brake lights are a safety and legal concern, and a stuck selector or a no-start condition can leave you stranded.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.