1. Fault Overview
When the MSB Fault Light remains constantly illuminated when the ignition is turned ON, and;
LED Displays the ‘P’ and ‘H’ LEDs flashing, alongside a beep every 30 seconds from the LED module’s buzzer.
OR
When the LCD screen logs a Tonal Alarm (horn) fault,
The fault conditions will be one of below:
Conditions for setting fault
- Disconnected/faulty tonal alarm
- Open/short circuit in wiring harness
- Internal MSB ECU fault.
After completing diagnosis and rectifying any faults, a full system test must then be performed and documented on the Systems Confirmation Test – MAX-SAFE Anti-Rollaway Brake System test sheet prior to returning the vehicle to service.
2. Diagnostic Procedure
Do not allow the warning alarm system to activate when performing this test.
STEP 1: Clear the fault by isolating the vehicle power supply at the batteries for at least 1 second. Reactivate the power supply to the vehicle.
Fault re-occurs on reactivating power supply: Continue to STEP 2 (Testing for an open circuit).
Fault does not occur upon reactivating power supply: Continue to STEP 5 (Testing for a short circuit).
STEP 2: Disconnect the tonal alarm. Bridge the 2 tonal alarm wires together. Isolate the vehicle’s power supply for a minimum of 1 second, and then re-connect the power supply.
Fault re-occurs on reactivating power supply: Continue to STEP 3.
Fault does not occur upon reactivating power supply: Replace tonal alarm.
Verify repair with Full System Test.
STEP 3: Locate MSB ECU. Disconnect the 12-way Deutsch Connector (black). Using a multi-meter, measure resistance between Pin 12 (orange/white) and Pin 1 (orange/white) of tonal alarm connector (H-Horn).
Verify GND circuit on pin 2 of tonal alarm connector.
Within specifications: Continue to STEP 4.
Not within specifications: Repair wiring harness/connections as required.
Verify repair with Full System Test.
STEP 4: Replace tonal alarm. Perform a Full System Test.
If the fault still appears: The ECU has failed. This scenario is unlikely: repeat all testing again to ensure that it is the ECU that has failed. If all testing has been repeated and testing still indicates that the ECU has failed, replace the ECU.
Verify repair with Full System Test.
STEP 5: (Testing for a short circuit)
After isolating and reactivating vehicle power supply, identify that ‘P’ & ‘H’ LEDs are not flashing, or that the LCD screen is not displaying a fault. Operate the system, and activate the tonal alarm circuit, by setting the door to OPEN and the park brake to OFF, then set the door to OFF. Ensure that the tonal alarm sounds whilst the door is OPEN, and the park brake OFF. Perform this cycle test until the system faults or until 10 cycles have been completed.
Fault does not occur upon reactivating power supply: Perform a Full System Test.
Fault re-occurs when Alarm circuit activated: Continue to STEP 6.
STEP 6: Locate MSB ECU. Disconnect the 12-way Deutsch Connector (black). Using a multi-meter, measure resistance between Pin 12 (orange/white) and Pin 1 (orange/white) of tonal alarm connector.
Verify GND circuit on pin 2 of tonal alarm connector (H-Horn).
Checking for shorted wiring to ground.
Within specifications: Continue to STEP 7.
Not within specifications: Repair wiring harness/connections as required.
Verify repair with Full System Test.
STEP 7: Replace tonal alarm. Perform a Full System Test.
If the fault still appears: The ECU has failed. This scenario is unlikely: repeat all testing again to ensure that it is the ECU that has failed. If all testing has been repeated and testing still indicates that the ECU has failed, replace the ECU.
Verify repair with Full System Test.
4. Full System Test
Undertake a full system test of the MAX-SAFE Brake System and document the results on the test sheet found within the document Systems Confirmation Test – MAX-SAFE Anti-Rollaway Brake System prior to returning the vehicle to service.
Should the testing outlined within the Systems Confirmation Test fail for any reason, the system must be thoroughly inspected, diagnosed and repaired, as per the relevant Diagnostic Process document, prior to the vehicle being returned to service.
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