Fault Code 163: Demanded Brake Application Pressure
J1939: SA 3 SPN 8484 FMI 9, 13, 19
Overview
The Transmission Control Module (TCM) receives the vehicle’s Demanded Brake Application Pressure message from a vehicle Electronic Control Unit (ECU) over the Primary Data Link (J1939A). This information is used to determine transmission operation.
Detection
The TCM monitors Demanded Brake Application Pressure messages. If messages are not received or are invalid, the fault is set Active.
Conditions to Set Fault Code Active
FMI 9 - Abnormal Update Rate: Demanded Brake Application Pressure message not received for 10 seconds.
FMI 13 - Out of Calibration: Demanded Brake Application Pressure message not available for 10 seconds.
FMI 19 – Received Network Data In Error: Demanded Brake Application Secondary Pressure messages invalid for 10 seconds.
Fallback
FMI 9, 13, 19:
- If Fault Code 156, 161 and 163 are all Active:
- Amber warning lamp on
- Urge to Move and Creep Mode prohibited
- Hill Start Aid prohibited
- Transmission may not allow a shift out of Neutral
Note: Vehicle may have additional fallback modes. Refer to OEM.
Conditions to Set Fault Code Inactive
FMI 9, 13, 19: Demanded Brake Application Pressure messages received and valid for 10 seconds.
Possible Causes
FMI 9, 13, 19:
- Vehicle Components
- Demanded Brake Application Pressure message not enabled
- Other vehicle ECU(s) faulted
- Vehicle Harness - Primary Data Link (J1939A)
- Wiring shorted to power, shorted to ground or open
- Terminals bent, spread, corroded, or loose
Note: Refer to OEM for troubleshooting a failed system.
Additional Tools
- None
Fault Code 163 Troubleshooting
Set vehicle parking brake and chock wheels.
Record transmission fault codes, FMIs, occurrences, and timestamps from 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 9, 19 is Active or Inactive, Go to Step B
If Fault Code 163 FMI 13 is Active, refer to OEM and enable vehicle Demanded Brake Application Pressure message (SPN 8484). Go to Step V
If Fault Code 163 FMI 13 is Inactive, Go to Step V
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 “- 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 of the vehicle Demanded Brake Application Pressure message (SPN 8484). Go to Step V
If readings are in range and no fault was found, the intermittent nature of the fault makes it likely that the problem is in the vehicle Demanded Brake Application Pressure message (SPN 8484). 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 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 vehicle operates properly, test complete.
If Fault Code 163 sets Active, Go to Step A
If a fault code other than 163 sets Active, troubleshoot per Fault Code Isolation Procedure Index.