Fault Code 166: Secondary Accelerator Pedal Position
J1939: SA 3 SPN 29 FMI 9, 13, 19
Overview
The Transmission Control Module (TCM) receives the vehicle's Accelerator Pedal Position 1 message from a vehicle Electronic Control Unit (ECU) over the Primary Data Link (J1939A). The Accelerator Pedal Position 1 message provides the TCM with the driver's demand to launch and accelerate the vehicle.
The TCM also receives the Accelerator Pedal Position 1 message over the Secondary Data Link (J1939B). The Secondary Data Link is used in the event that the Primary Data Link is inoperative and allows the transmission to operate in a degraded mode.
The Primary Data Link (J1939A) is connected to the TCM at the 20-Way TCM Vehicle Harness Connector. The Secondary Data Link (J1939B) is connected to the TCM at the 20-Way TCM Body Harness Connector.
Detection
The TCM monitors Accelerator Pedal Position 1 messages on the Secondary Data Link (J1939B). If messages are not received or are invalid, the fault is set Active.
Conditions to Set Fault Code Active
FMI 9 - Abnormal Update Rate: Accelerator Pedal Position 1 message not received for 5 seconds.
FMI 13 - Out of Calibration: Accelerator Pedal Position 1 message not available for 5 seconds.
FMI 19 - Received Network Data in Error: Accelerator Pedal Position 1 messages invalid for 5 seconds.
Fallback
FMI 9, 13, 19:
- Amber warning lamp on
- If Fault Code 115, 171, or 185 are Active and the transmission is in gear:
- Coast Mode and Neutral Coast prohibited
- Urge to Move and Creep Mode prohibited
- Inertia Brake activation prohibited
- Upshifts prohibited
- Clutch engagements prohibited
- Non-Neutral modes prohibited
- PTO mode prohibited
- Hill Start Aid prohibited
- If Fault Code 115, 171, or 185 are Active and the transmission is not in gear:
- 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
- Hill Start Aid prohibited
Conditions to Set Fault Code Inactive
FMI 9, 13, 19: Accelerator Pedal Position 1 messages received and valid for 10 seconds.
Possible Causes
FMI 9, 13, 19:
- Vehicle Components
- Accelerator Pedal Position 1 message not enabled on Secondary Data Link (J1939B)
- Other vehicle ECU(s) faulted
- Vehicle Harness - Secondary Data Link (J1939B)
- 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 166 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 166 is Inactive and there are other Active vehicle or transmission fault codes, troubleshoot all Active fault codes. Go to Step V
If Fault Code 166 FMI 9, 19 is Active or Inactive, Go to Step B
If Fault Code 166 FMI 13 is Active, refer to OEM and enable vehicle Accelerator Pedal Position 1 message (SPN 29). Go to Step V
If Fault Code 166 FMI 13 is Inactive, Go to Step V
Key on with engine off.
Connect ServiceRanger.
Go To “Data Monitor”.
Select “Position”.
Select “Percent accelerator pedal position 2”.
Select all “- 29” SPN sources.
Note: Not all sources will indicate a value.
Monitor 29 - Percent accelerator pedal position 2 value. Record reading in table.
Depress and hold the accelerator pedal.
Monitor 29 - Percent accelerator pedal position 2 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 Accelerator Pedal Position 1 message (SPN 29) on Secondary Data Link (J1939B). 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 Accelerator Pedal Position 1 message (SPN 29) on Secondary Data Link (J1939B). Contact OEM for further diagnostic instructions. Go to Step V
| Accelerator Pedal State | Parameter | Range | Reading(s) |
|---|---|---|---|
| Released | 29 - Percent accelerator pedal position 2 | 0% | |
| Depressed | 29 - Percent accelerator pedal position 2 | Greater than 0% |
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 165 sets Active, Go to Step A
If a fault code other than 165 sets Active, troubleshoot per Fault Code Isolation Procedure Index