Fault Code 162: Brake Secondary Pressure
J1939: SA 3 SPN 118 FMI 9, 13, 18, 19
Overview
The Transmission Control Module (TCM) receives the vehicle’s Brake Secondary Tank Pressure message from a vehicle Electronic Control Unit (ECU) over the Primary Data Link (J1939A). The Brake Secondary Tank Pressure message is used as a secondary vehicle air pressure input by the TCM to ensure adequate air pressure is maintained for transmission operation.
Note: The vehicle air supply comes from a dedicated transmission air tank. The primary and secondary air gauges in the cab of the vehicle may not reflect the pressure of the transmission air supply line. The transmission air tank is often isolated from the rest of the vehicle air system with a Pressure Protection Valve and/or Check Valve.
Detection
The TCM monitors Brake Secondary Tank 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: Brake Secondary Tank Pressure message not received for 10 seconds.
FMI 13 - Out of Calibration: Brake Secondary Tank Pressure message not available for 10 seconds.
FMI 18 - Data Valid but Below Normal (Moderately Severe): Brake Secondary Tank Pressure and Transmission Air Supply Pressure reported greater than 90 psi (6.2 bar) and then fell below 80 psi (5.5 bar) with the vehicle stationary and the transmission in Neutral.
FMI 19 – Received Network Data In Error: Brake Secondary Tank Pressure messages invalid for 10 seconds.
Fallback
FMI 9, 13, 19:
- Amber warning lamp on
- No degraded modes
FMI 18:
- Coast Mode and Neutral Coast prohibited
- Urge to Move and Creep Mode prohibited
- Inertia Brake activation prohibited
- Upshifts prohibited
- Clutch disengagements prohibited
- Non-Neutral modes prohibited
- PTO mode prohibited
Conditions to Set Fault Code Inactive
FMI 9, 13, 19: Brake Secondary Tank Pressure messages received and valid for 10 seconds.
FMI 18: Brake Secondary Tank Pressure above 90 psi.
Possible Causes
FMI 9, 13, 19:
- Vehicle Components
- Brake Secondary Tank 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
FMI 18:
- Vehicle Components
- Air system
Note: Refer to OEM for troubleshooting a failed system.
Additional Tools
- None
Fault Code 162 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 162 is Inactive and there are other Active vehicle or transmission fault codes, troubleshoot all Active fault codes. Go to Step V
If Fault Code 162 FMI 9, 19 is Active or Inactive, Go to Step B
If Fault Code 162 FMI 13 is Active, refer to OEM and enable vehicle Brake Secondary Tank Pressure message (SPN 118). Go to Step V
If Fault Code 162 FMI 13 is Inactive, Go to Step V
If Fault Code 162 FMI 18 is Active or Inactive, Go to Step C
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 “Brake secondary pressure”.
Select all “- 118” SPN sources.
Note: Not all sources will indicate a value.
Monitor 118 - Brake secondary pressure value. Record reading in table.
Monitor vehicle in-dash air pressure gauge. 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 vehicle air system or Brake Secondary Tank Pressure message (SPN 118). 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 air system or Brake Secondary Tank Pressure message (SPN 118). Contact OEM for further diagnostic instructions. Go to Step V
| Parameter/ Source | Range | Reading(s) |
|---|---|---|
| 118 - Brake secondary pressure | Within 0-20 psi of Vehicle air pressure | |
| Vehicle in-dash secondary air pressure gauge | 100-135 psi |
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”.
From “Default Parameter Files” tab, select “Transmission Pressure”.
Monitor 520524 - Line Pressure Feedback value. Record reading in table.
Select “Pressure”.
Select “Brake secondary pressure”.
Select all “- 118" SPN sources.
Note: Not all sources will indicate a value.
Monitor 118 - Brake secondary pressure value. Record reading in table.
Monitor vehicle in-dash air pressure gauge. Record reading in table.
Compare reading(s) in table.
If readings are out of range, refer to OEM guidelines for repair or replacement of vehicle air system. 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 air system. Contact OEM for further diagnostic instructions. Go to Step V
| Parameter/ Source | Range | Reading(s) |
|---|---|---|
| 520524 - Line Pressure Feedback | Within 0–20 psi of Vehicle air pressure | |
| 118 - Brake secondary pressure | Within 0–20 psi of Vehicle air pressure | |
| Vehicle in-dash secondary air pressure gauge | 100–135 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 162 sets Active, Go to Step A
If a fault code other than 162 sets Active, troubleshoot per Fault Code Isolation Procedure Index.