UltraShift PLUS
TRTS0940 EN-US
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July 2024 - A

Fault Code 36: J1939 Engine Message

J1587: MID 130 SID 231 FMI 14

J1939: SA 3 SPN 639 FMI 14

Overview

The J1939 Data Link is a Controller Area Network (CAN) communication bus. The UltraShift PLUS transmission uses the J1939 Data Link to communicate with other ECUs (ABS, Engine, Body Controller, etc.). The Transmission Electronic Control Unit (TECU) sends and receives messages from other ECUs on the data link to determine when to initiate a shift, hold shifts, command engine torque to make shifts, as well as other functions. Proper operation of the J1939 Data Link is critical for shift performance. Fault Code 36 indicates the TECU can communicate with other ECUs on the J1939 Data Link but has lost communication with the Engine ECU.

Detection

TECU has either lost communication or received erratic signals from the Engine ECU over the J1939 Data Link and the TECU has not detected any low or weak battery system fault codes.

Conditions to Set Fault Code Active

FMI 14 – Special Instructions: TECU has either lost communication or has received erratic signals from the Engine ECU over the J1939 Data Link for 5 seconds or longer.

Fallback

FMI 14

  • “F” flashes in gear display.
  • Service light flashes (if equipped).
  • If vehicle is configured for the J1939 Start Enable feature the engine does not crank.
  • If fault occurs during power up, the transmission requires the driver to manually synchronize shifts with the throttle.
  • If fault occurs while driving, transmission remains in its current gear until the vehicle stops. Transmission then requires the driver to manually synchronize shifts with the throttle.

Conditions to Set Fault Code Inactive

FMI 14: TECU receives messages across the data link for at least 10 seconds.

Possible Causes

FMI 14

  • J1939 Data Link
    • Wiring shorted to ground, shorted to power or open
    • Excessive electrical noise
    • Missing or additional terminating resistors
  • Engine ECU
    • Internal failure
  • Vehicle Harness
    • Wiring shorted to ground, shorted to power or open
  • Engine Harness
    • Wiring shorted to ground, shorted to power or open

Component Identification

_Graphics/LineArt/TRTS0940_FC35-36_ID1.png

1. 38-Way Vehicle Harness Connector

2. Transmission Electronic Control Unit (TECU)

3. 9-Way Diagnostic Connector (in cab)

_Graphics/LineArt/TRTS0940_FC35_Wiring.png

1. Transmission Electronic Control Unit (TECU)

2. 38-Way Vehicle Harness Connector

3. 9-Way Diagnostic Connector (Black) - OEM Specific CD (in cab)

4. 9-way Diagnostic Connector (Green) - OEM Specific CD (in cab)

5. 9-way Diagnostic Connector (Green) - OEM Specific FG (in cab)

_Graphics/LineArt/Wiring-Key-EPS.png

Fault Code 36 Troubleshooting

A
Purpose:Check for Active or Inactive fault codes.

  1. Record the transmission fault codes, FMIs, occurrences, and timestamps from the Service Activity Report created during the Diagnostic Procedure.

    Note: Fault Code 36 indicates an issue with communication over the J1939 data link between the Engine ECU and the Transmission TECU. All wiring and pin outs for connectors are OEM proprietary. Refer to OEM guidelines for proper documentation.

B
Purpose:Use Product Diagnostic (PD) Mode to locate intermittent failures.

  1. Set parking brake and chock wheels.

  2. Place transmission in PD Mode. See more about Product Diagnostic (PD) Mode.

    Note: Transmission does not enter PD Mode when there are Active fault codes.

    _Common/_Graphics/PD_GearDisplay.png

  3. Wiggle J1939 Data Link wiring and Vehicle Harness wiring throughout the vehicle. Look for signs of pinched or chafed wiring. Verify all connections are clean and tight.

  4. Exit PD Mode by powering down.

    Note: Allow 2–3 minutes for the TECU to perform a complete power-down sequence before proceeding.

  • If Fault Code 35 or Fault Code 36 became Active while wiggling the J1939 Data Link or the Vehicle Harness, refer to OEM guidelines for repair or replacement of J1939 Data Link. Go to Step V

  • If no fault codes became Active, Go to Step C

C
Purpose:Verify TECU location on the vehicle J1939 Data Link.

  1. Key off.

  2. Refer to the OEM and identify the TECU location on the vehicle J1939 Data Link at the 9-Way Diagnostic Connector.

  • If Black 9-Way Diagnostic Connector, Go to Step D

  • If Green 9-Way Diagnostic Connector on Pin C and Pin D, Go to Step D

  • If Green 9-Way Diagnostic Connector on Pin F and Pin G, refer to OEM guidelines for diagnosing a communication issue between the Engine ECU and TECU.

D
Purpose:Verify proper resistance exists on the J1939 Data Link.

  1. Key off.

    Note: Allow 2–3 minutes for the TECU to perform a complete power-down sequence before proceeding.

  2. Measure resistance between 9-Way Diagnostic Connector Pin C and Pin D. Record reading(s) in table.

    _Graphics/LineArt/TRTS0940_FC36_DiagPinCandD-Ohms.png

  3. Compare reading(s) in table.

  • If readings are in range, Go to Step E

  • If readings are out of range, refer to OEM guidelines for repair or replacement of terminating resistors, ECUs or J1939 data link wiring. Go to Step V

PinsRangeReading(s)
C to D50–70 ohms
E
Purpose:Verify connection across J1939 Positive Pin (+) between Engine ECU and TECU.

  1. Key off.

    Note: Allow 2–3 minutes for the TECU to perform a complete power-down sequence before proceeding.

  2. Disconnect 38-Way Vehicle Harness Connector from TECU. Inspect connector for loose terminals, corrosion, and bent or spread pins.

  3. Disconnect Engine ECU Harness Connector from the Engine ECU. Inspect connector for loose terminals, corrosion, and bent or spread pins.

  4. Measure resistance between 38-Way Vehicle Harness Connector Pin 3 and J1939 Positive Pin (+) on Engine ECU Connector. Record reading(s) in table.

    _Graphics/LineArt/TRTS0940_FC36_OEMECUtoVPin3.png

    Note: Refer to OEM guidelines for location of Engine ECU J1939 Positive Pin (+).

  5. Compare reading(s) in table.

  • If readings are in range, Go to Step F

  • If readings are out of range, refer to OEM guidelines for repair or replacement of J1939 Data Link. Go to Step V

PinsRangeReading(s)
3 to Engine J1939 Positive (+)0.0–0.3 ohms
F
Purpose:Verify connection across J1939 Negative Pin (-) between Engine ECU and TECU.

  1. Key off.

  2. Measure resistance between 38-Way Vehicle Harness Connector Pin 2 and J1939 Negative Pin (-) on Engine ECU Connector. Record reading(s) in table.

    _Graphics/LineArt/TRTS0940_FC36_OEMECUtoVPin2.png

    Note: Refer to OEM guidelines for location of Engine ECU J1939 Negative Pin (-).

  3. Compare reading(s) in table.

  • If readings are out of range, refer to OEM guidelines for repair or replacement of J1939 Data Link. Go to Step V

  • If readings are in range, an intermittent wiring issue exists within the J1939 Data Link, refer to OEM guidelines for repair or replacement of J1939 Data Link. Go to Step V

PinsRangeReading(s)
2 to Engine J1939 Negative (-)0.0–0.3 ohms
V
Purpose:Verify repair.

  1. Key off.

  2. Reconnect all connectors and verify that all components are properly installed.

  3. Key on with engine off.

  4. Clear fault codes using ServiceRanger.

  5. Drive vehicle and attempt to reset the code or duplicate the previous complaint.

  6. Check for fault codes using ServiceRanger.