The Transmission Control Module (TCM) receives the vehicle’s Demanded Brake Application Pressure signal message over the Primary Data Link. This information is used to determine transmission operation.
The TCM monitors the Demanded Brake Application Pressure signal message. If a failure is detected the fault is set Active.
FMI 9 - Abnormal Update Rate: Demanded Brake Application Pressure signal not received for 10 seconds.
FMI 13 - Out of Calibration: Demanded Brake Application Pressure message not available for 5 seconds.
FMI 19: Demanded Brake Application Pressure message invalid for 5 seconds.
FMI 9, 13, 19:
FMI 9, 13, 19: Demanded Brake Application Pressure signal received and valid for 10 seconds.
FMI 9, 13, 19:
Set vehicle parking brake and chock wheels.
Record the transmission fault codes, FMIs, occurrences, and timestamps from the Service Activity Report created during the Diagnostic Procedure.
If Fault Code 163 is Inactive and there are other Active vehicle or transmission fault codes, troubleshoot all Active fault codes. Go to Step V
If Fault Code 163 FMI 13 is Active, refer to OEM and enable vehicle Demanded Brake Application Pressure SPN 8484. Go to Step V
If Fault Code 163 FMI 13 is Inactive, Go to Step V
If Fault Code 163 FMI 9 or 19 is Active or Inactive, Go to Step B
Key on with engine running.
Allow air pressure to build to governor cut off.
Key off.
Key on with engine off.
Connect ServiceRanger.
Go To “Data Monitor”.
Select “Pressure”.
Select “Demanded brake application pressure”.
Select all of the “- 8484” SPN sources.
Note: Not all sources will indicate a value.
Monitor 8484 - Demanded brake application pressure value. Record reading in table.
Depress and hold service brake.
Monitor 8484 - Demanded brake application pressure value. Record reading in table.
Compare reading(s) in table.
If readings are out of range, refer to OEM guidelines for repair or replacement of the Demanded brake application pressure signal message. Go to Step V
If readings are in range, no fault was found. The intermittent nature of the fault makes it likely that the problem is in the Demanded brake application pressure signal message. Contact OEM for further diagnostic instructions. Go to Step V
Service Brake State | Parameter | Range | Reading(s) |
---|---|---|---|
Released | 8484 - Demanded Brake Application Pressure | 0 PSI | |
Depressed | 8484 - Demanded Brake Application Pressure | Greater Than 0 PSI |
Key off.
Reconnect all connectors and verify that all components are properly installed.
Key on with engine off.
Connect ServiceRanger.
Go to “Fault Codes”.
Select “Clear All Faults”.
Operate vehicle and attempt to reset the fault code or duplicate the previous complaint.
Check for fault codes using ServiceRanger.
If no fault codes set and the vehicle operates properly, test complete.
If Fault Code 163 sets Active during operation, Go to Step A
If a fault code other than 163 sets Active, troubleshoot per Fault Code Isolation Procedure Index.