Faulty Signal
Faulty signal
Checking the diagnostic trouble codes (DTCs)
Check whether any diagnostic trouble codes (DTCs) are stored in the brake control module (BCM) or in the central electronic module (CEM).
Any diagnostic trouble codes (DTCs) stored in the brake control module (BCM) or central electronic module (CEM) must be remedied first.
Have fault causes been traced or remedied in the brake control module (BCM) or central electronic module (CEM)?
Yes - Checking the status
No - DONE
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Checking the status
- Ignition on.
Read off the status from the stop lamp switch.
Check the function of the stop lamp switch by carefully pressing and releasing the brake pedal.
Check that the status changes between "OFF" when the brake pedal is unaffected and "ON" when the brake pedal is depressed.
If the status of the stop lamp switch changes as described above when the brake pedal is depressed, the fault is intermittent at the moment.
Continue - Checking the power supply
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Checking the power supply
- Ignition on.
Check the power supply to the stop lamp switch. Take readings between stop lamp switch terminal #2 (cable harness side) and the ground terminal. The power supply must be approximately 12 V.
If there is no power supply:
Check the power supply circuit for stop lamp switch terminal #2 (cable harness side). Check for an open-circuit. Check for a short-circuit to ground. Check for a blown fuse in the circuit.
Remedy as necessary.
Other information
- Connecting the breakout box, B5254T7 Connecting the Breakout Box, Engine Control Module (ECM)
- Signal specification, B5254T7 Signal Specification
- For further information about the fuses and relays, see the Wiring Diagram.
- Stoplamp switch Service and Repair
- Checking wiring and terminals Checking Wiring and Terminals
Continue - Checking the component and wiring
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Checking the component and wiring
- Ignition off
- Check that the stop lamp switch is correctly installed.
Check the resistance of the stop lamp switch with the switch pressed in and with the switch released. Take readings between terminals #1 and #2 (component side) on the stop lamp switch.
Hint: The stop lamp switch must be closed when the brake pedal is depressed. The resistance of the stop lamp switch must be infinite when the brake pedal is unaffected.
Check the stop lamp switch and engine control module (ECM) connectors. Check for contact resistance. Check for oxidation.
Check the cable. Check for loose connections. Check for an open-circuit. Check for a short-circuit to ground. Check for a short-circuit to supply voltage.
Take readings between:
- Engine Control Module (ECM) #B30 (#C30) and brake light switch #1.
Remedy as necessary.
Other information
- Connecting the breakout box, B5254T7 Connecting the Breakout Box, Engine Control Module (ECM)
- Signal specification, B5254T7 Signal Specification
- Checking wiring and terminals Checking Wiring and Terminals
Continue - Verification
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Verification
Verification
Hint: After carrying out the repair, check that the fault has been remedied.
- Ignition off
- Reconnect the connectors, reinstall components etc.
- Ignition on.
Read off the status from the stop lamp switch.
Check the function of the stop lamp switch by carefully pressing and releasing the brake pedal.
Check that the status changes between "OFF" when the brake pedal is unaffected and "ON" when the brake pedal is depressed.
If the status of the stop lamp switch changes as described above when the brake pedal is depressed, the fault has been remedied.
Is the function OK?
Yes - VERIFIED
No - VERIFICATION FAILED
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VERIFIED - FAULT FOUND
VERIFICATION FAILED - Fault-tracing information
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Fault-tracing information
Attempt New Test - Checking the diagnostic trouble codes (DTCs)
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