Fault Code 156: Brake Pedal Position
J1939: SA 3 SPN 521 FMI 13, 19
Overview
The Transmission Control Module (TCM) receives the vehicle’s Brake Pedal Position 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 Brake Pedal Position messages. If messages are not available or are invalid, the fault is set Active.
Conditions to Set Fault Code Active
FMI 13 - Out of Calibration: Brake Pedal Position message not available for 10 seconds.
FMI 19 – Received Network Data in Error: Brake Pedal Position messages invalid for 10 seconds.
Fallback
FMI 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
Conditions to Set Fault Code Inactive
FMI 13, 19: Brake Pedal Position messages available and valid for 10 seconds.
Possible Causes
FMI 13, 19:
- Vehicle Components
- Brake Pedal Position 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 156 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 156 is Inactive and there are other Active vehicle or transmission fault codes, troubleshoot all Active fault codes. Go to Step V
If Fault Code 156 FMI 9, 19 is Active or Inactive, refer to OEM guidelines for repair of the vehicle Brake Pedal Position message (SPN 521). Go to Step V
If Fault Code 156 FMI 13 is Active, refer to OEM and enable vehicle Brake Pedal Position message (SPN 521). Go to Step V
If Fault Code 156 FMI 13 is Inactive, 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 156 sets Active, Go to Step A
If a fault code other than 156 sets Active, troubleshoot per Fault Code Isolation Procedure Index.