Faulty Signal

Faulty signal

Checking diagnostic trouble codes in the central electronic module (CEM) and the engine control module (ECM)
If there are diagnostic trouble codes (DTCs) for the brake pedal position sensor or stop lamp switch stored in the engine control module (ECM) or central electronic module (CEM), these must be fault traced first.

Were diagnostic trouble codes (DTCs) stored for the pedal position sensor or the stop lamp switch?

Yes - DONE

No - Checking the control module and sensor connectors

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Checking the control module and sensor connectors

Hint: The cause of the diagnostic trouble code (DTC) may be in the circuit for the stop lamp switch or for the pedal position sensor.








- Ignition off
- Check the connectors for the brake control module (BCM), the stop lamp switch and the pedal position sensor. Check for contact resistance and oxidation
- Reinstall the components, reconnect the connectors etc.
- Ignition on
- Read off the status of the stop lamp switch and the position of the pedal position sensor.
Depress and release the brake pedal. The value must change between OFF and ON and the position of the pedal position sensor must be updated.

Other information
- To disconnect the connector for the brake control module (BCM), see Connecting the breakout box, brake control module (BCM) Connecting the Breakout Box, Brake Control Module (BCM)
- To access the stop lamp switch, see Stop lamp switch, replacing Service and Repair
- To access the pedal position sensor, see Pedal sensor power brake booster, replacing Service and Repair
- Checking wiring and terminals Checking Wiring And Terminals

Select an option:
1. The value for the stop lamp switch does not change
2. The value for the pedal position sensor is not updated
3. These values are OK.





Does the value change?

1 - Checking the fuse, wiring and sensors

2 - Signal outside its permitted range

3 - No Fault Found

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Checking the fuse, wiring and sensors




Check that the fuse for the stop lamp circuit is intact. If the fuse is blown, first check the circuit for the stop lamp switch before replacing the fuse. Check for a short-circuit to supply.
If the fuse is intact, check the circuit for the stop lamp switch. Check for an open-circuit and a short-circuit to ground.
Remedy as necessary.

Other information
- To connect the breakout box to the brake control module (BCM), see Connecting the breakout box, brake control module (BCM) Connecting the Breakout Box, Brake Control Module (BCM)
- To connect the breakout box to the Engine control module (ECM), see: Connecting the breakout box, B5244T5, B5254T2 Connecting the Breakout Box
- See Connecting breakout box for Central Electronic Module (CEM). Connecting the breakout box Connecting the Breakout Box, Central Electronic Module (CEM)
- To replace the stop lamp switch, see Stop lamp switch, replacing Service and Repair
- Checking wiring and terminals Checking Wiring And Terminals





Was a fault detected?

Yes - Verification

No - No Fault Found

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Signal outside its permitted range

Checking the connectors








- Ignition off
- Check the brake control module (BCM) and pedal position sensor connectors. Check for contact resistance and oxidation
- Reinstall the components, reconnect the connectors etc.
- Connect the breakout box
- Ignition on
- Read off the signal from the pedal position sensor.
Depress the brake pedal. Check that the pedal signal is updated.

Other information
- To connect the breakout box, see Connecting the breakout box, brake control module (BCM) Connecting the Breakout Box, Brake Control Module (BCM)
- Checking wiring and terminals Checking Wiring And Terminals.









Was the signal updated?

Yes - Fault Found

No - Checking wiring and sensors

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Checking wiring and sensors
Check the wiring between the pedal position sensor:
- terminal #1 and control module terminal #7 (#A7)
- terminal #2 and control module terminal #5 (#A5)
- terminal #3 and control module terminal #3 (#A3).
check for an open-circuit, a short-circuit to ground and a short-circuit to supply voltage.

Hint: Connect an ohmmeter between terminals #2 and #3 on the pedal position sensor connector.
The resistance must be approximately 0.5 kohms with the brake pedal unaffected and approximately 2.5-3 kohms when the brake pedal is depressed.

Connect an ohmmeter between terminals #1 and #3 on the pedal position sensor connector.
The resistance must be approximately 2.5-3 kohms with the brake pedal unaffected and approximately 0.5 kohms with depressed brake pedal.

Replace the pedal position sensor if the resistance is incorrect.

Replace the pedal position sensor if no fault is found.

Other information
- To connect the breakout box, see Connecting the breakout box, brake control module (BCM) Connecting the Breakout Box, Brake Control Module (BCM)
- To replace the pedal position sensor, see Pedal sensor power brake booster, replacing Service and Repair
- For information about signals, see Signal specification, brake control module (BCM) with DSTC (dynamic stability and traction control) Signal Specification
- Checking wiring and terminals Checking Wiring And Terminals










Continue - Verification

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Verification

Hint: After carrying out the repair, check that the fault has been remedied.








- Ignition off
- Reinstall the components, reconnect the connectors etc.
- Ignition on
- Read off the signal from the pedal position sensor.
Depress the brake pedal. Check that the pedal signal is updated.









Was the signal updated?

Yes - Fault Found

No - Fault-tracing information

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Fault-tracing information




Information

Fault-tracing information
The fault should have been detected and remedied. As this is not the case fault-tracing has failed.
Exit fault-tracing for this diagnostic trouble code (DTC) or make another attempt.

Do you want to exit fault-tracing?

Yes - FAULT-TRACING FAILED

No - Attempt New Test

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FAULT-TRACING FAILED - FAULT-TRACING FAILED

Attempt New Test - Checking the connectors

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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 of the stop lamp switch.
Depress and release the brake pedal. The value must change between OFF and ON.





Does the value change?

Yes - VERIFIED

No - VERIFICATION FAILED

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VERIFIED - Fault Found

VERIFICATION FAILED - Fault-tracing information

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Fault-tracing information
Information
FAULT-TRACING FAILED - FAULT-TRACING FAILED

Attempt New Test - Checking diagnostic trouble codes in the central electronic module (CEM) and the engine control module (ECM)

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