SPN 1045 — Stop Lamp Switch #1
Safe to driveDrivable, but watch it yourself
Updated: 2026-11-10
J1939 code SPN 1045. Below — how the fault is worded at the factory by Bendix ABS/ESP, KAMAZ EBS3, Renault Trucks and WABCO ABS/ESC, and what the second half of the code (FMI) means in the standard.
How to check it yourself
The brake pedal switch (stop signal No. 1). It switches on the stop lights and sends the units the 'brake pressed' signal.
What it should read
| Signal 'pressed' and 'not pressed' | changes when the pedal is pressed and released |
| Brake pedal adjustment | per the manufacturer's manual |
Check order
- Press and release the pedal with the ignition on and watch the switch state in diagnostics. If it does not change — the switch or the pedal adjustment.
- FMI 2, 4, 7 (switch faulty or no communication channel): measure the switch with a multimeter in both positions.
- If the stop lights do not come on — check the fuse and the common stop light line.
Common causes — from most to least frequent
- Stop light switch.
- Pedal adjustment.
- Burnt stop light or fuse.
- Open communication channel to the unit.
Bendix ABS/ESPKAMAZ EBS3Renault TrucksWABCO ABS/ESC
Bendix ABS/ESP
| FMI 2 | Stop Lamp Switch Defective |
| FMI 4 | Brake Lamp Input Mismatch with Brake Lamp Output |
| FMI 7 | Stop Lamp Switch Not Detected |
EBS3 brakes (WABCO)
| FMI 4 | Brake light switch 1: voltage below normal or short circuit |
| FMI 5 | Brake light switch 1: current below normal or open circuit |
Renault Trucks
| FMI 7 | VECU communication channel fault (the “stop brake switch” message is missing). Repair: Make sure the VECU actually sends messages over the CAN data bus. Check the continuity of the CAN data bus wiring (X1/1, X1/2). |
WABCO ABS/ESC
| FMI 3 | E401 and E404 Version Only. Pressure Sensor Shorted to UBATT; Pressure Sensor Shorted to UBATT |
| FMI 5 | E401 and E404 Version Only. Pressure Sensor Shorted to Ground; Pressure Sensor Shorted to Ground |
| FMI 7 | Brake light switch 1 — mechanical fault |
What FMI means in J1939
Can I keep driving
Safe to drive. Below — how much time you have and what happens if you keep going.
What happens if you keep driving
This is an electrical fault: an open, a short or a bad contact in the sensor circuit. The value it measures is most likely fine.
You can drive. But until the circuit is repaired this system runs blind and cannot warn you about a real failure.
Nearby: other
- SPN 970Engine Auxiliary Shutdown Switch
- SPN 974Remote Accelerator Pedal Position
- SPN 979Remote PTO Preset Speed Control Switch
- SPN 1041Start Signal Indicator
- SPN 1042Tractor/Trailer Electronic Interface
- SPN 1048Backup Pneumatic Pressure Control, Axle 1
- SPN 1054Backup Pneumatic Pressure Control, Axle 3
- SPN 1056Electronic Pressure Control, Trailer Control
- SPN 1057Backup Pneumatic Pressure Control, Trailer Control
- SPN 1062Lining Wear Sensor, Axle 2, Left
Related codes
- SPN 1065Lining Wear Sensor, Axle 3, Right
- SPN 1068Brake Signal Sensor #2
- SPN 1081"Wait to Start" Lamp
- SPN 925Auxiliary Output #2
- SPN 920Audible Alarm
- SPN 1188Turbocharger 1 Wastegate Actuator
- SPN 1194Anti-Theft System Encryption Key Present Indicator
- SPN 1213Malfunction Indicator Lamp (MIL)
Makes with this code
Scanner threw several codes at once? Paste the whole list — we will show which one is the root cause and which ones simply followed.