Fault Code 991: SCR Thermal Management Active
J1939: SA 3 SPN 5400 FMI 9, 13, 19
Overview
The Transmission Control Module (TCM) receives the vehicle’s Selective Catalytic Reduction (SCR) Thermal Management Active 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 SCR Thermal Management Active 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: SCR Thermal Management Active message not received for 5 seconds.
FMI 13 - Out of Calibration: SCR Thermal Management Active message not available for 5 seconds.
FMI 19: Received Network Data in Error: SCR Thermal Management Active messages invalid for 5 seconds.
Fallback
FMI 9, 13, 19:
- Amber warning lamp on
- Coast Mode and Neutral Coast prohibited
Conditions to Set Fault Code Inactive
FMI 9, 13, 19: SCR Thermal Management Active messages received and valid for 10 seconds.
Possible Causes
FMI 9, 13, 19:
- Vehicle Components
- Vehicle SCR Thermal Management Active 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 991 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 991 is Inactive and there are other Active vehicle or transmission fault codes, troubleshoot all Active fault codes. Go to Step V
If Fault Code 991 FMI 13 is Active, refer to OEM and enable vehicle SCR Thermal Management Active message (SPN 5400). Go to Step V
If Fault Code 991 FMI 13 is Inactive, Go to Step V
If Fault Code 991 FMI 9 or 19 is Active or Inactive, refer to OEM guidelines for repair of the vehicle SCR Thermal Management Active message (SPN 5400). 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 991 sets Active, Go to Step A
If a fault code other than 991 sets Active, troubleshoot per Fault Code Isolation Procedure Index.