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Check DTC’s in the gearbox for faults that could prevent RELS operation Check wiring (1) from BCS to relay and (2) from relay to Allison ECU Replace the relay between BCS and Allison ECU
What you'll see
No driver-visible symptom recorded.
System reaction
No ICL warning; DTC only. Vehicle will consume more fuel than normal. Higher than normal load on brakes during BSB / AHH
Diagnostic depth
The DTC is set to active if the following is true for more than 10 seconds: - The BCS is requesting Disengage Driveline Request - The vehicle is stationary (indirectly due to Disengage Driveline Req). - The gearbox is warm enough for the function to engage on the gearbox (> 70 Deg C) - The engine status is such that the function can operate on the gearbox (speed between 400 to 700 rpm. Engine torque mode also checked) - The gearbox is in 1st gear - Accelerator pedal is not touched - The input shaft is not stationary (the input shaft rotates during RELS) The DTC is set to inactive if: - The BCS stops requesting Disengage Driveline Request DTC is only detected if the bus is equipped with an Allison gearbox and RELS is enabled The DTC is not set to active in the following cases: - Engine start is active. - Supply voltage is below 19 Volt. - Supply voltage is above 35 Volt.
Malfunction of the relay connecting the BCS and Allison ECUs Malfunction of the gearbox