Fault Code 988: Rock Free Mode Message
J1939: SA 3 SPN 12949 FMI 9, 13, 19
Overview
The Endurant HD Pro transmission incorporates a Rock Free Mode feature that allows the driver to perform a vehicle “rocking” maneuver by depressing and releasing the vehicle accelerator pedal. This maneuver is useful in situations where the vehicle’s wheels are stuck in terrain depressions that are preventing vehicle progress. When Rock Free Mode is required the Transmission Control Module (TCM) receives a request (Input) for Rock Free Mode operation, determines if operating conditions are suitable, implements the change, and supplies a signal (Output) notification. Reference Endurant HD Driver Instructions TRDR0955 for Rock Free Mode operation.
The TCM can be configured to activate Rock Free Mode with messages over the vehicle Primary Data Link J1939A or from a switch circuit hardwired directly to the TCM. The TCM is equipped to receive 4 switch inputs and control 3 relay outputs that can be configured in an Input/Output (I/O) Package to support various vocational features.
If the TCM is configured to "J1939 Message" Rock Free Mode operation messages are exchanged between the TCM and a OEM vehicle ECU. If the TCM is configured to " TCM Hardwired Switch", Rock Free Mode operation is controlled by Input and Output signals from a hardwired switch circuit.
The Rock Free Mode circuit is connected to the TCM in the 20-Way TCM Body Harness Connector. The Rock Free Mode circuit is installed by the OEM or body builder. The Rock Free Mode circuit is installed by the OEM or body builder. Reference Input / Output Calibration in the Appendix for recommended Rock Free Mode circuit wiring diagrams.
Detection
The TCM monitors Rock Free Mode 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: Rock Free Mode messages not received for 5 seconds.
FMI 13 – Out of Calibration: Rock Free Mode message not available for 5 seconds.
FMI 19 – Received Network Data in Error: Rock Free Mode messages invalid for 5 seconds.
Fallback
FMI 9, 13, 19:
- Amber warning lamp on
- No degraded modes
- Rock Free Mode will not function
Conditions to Set Fault Code Inactive
FMI 9, 13, 19: Rock Free Mode messages received and valid for 10 seconds.
Possible Causes
FMI 9, 13, 19:
- Vehicle Components - Vehicle ECU(s)
- Rock Free Mode message not enabled
- Other vehicle ECU(s) faulted
- Vehicle Harness - Primary Data Link (J1939A)
- Shorted to power, shorted to ground or open circuit
- Terminals bent, spread, corroded, or loose
Fault Code 988 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 988 is Inactive and there are other Active vehicle or transmission fault codes, troubleshoot all Active fault codes. Go to Step V
If Fault Code 988 FMI 9 or 19 is Active or Inactive, refer to OEM guidelines for repair of the vehicle Rock Free Mode message (SPN 12949). Go to Step V
If Fault Code 988 FMI 13 is Active, refer to OEM and enable Rock Free Mode message (SPN 12949). Go to Step V
If Fault Code 988 FMI 13 is Inactive, Rock Free Mode is properly configured. Go to Step V.
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 988 sets Active, Go to Step A
If a fault code other than 988 sets Active, troubleshoot per the Fault Code Isolation Procedure Index.