3406E, C-10, C-12, C-15, C-16 and C-18 On-highway Engines Caterpillar


Powertrain Data Link Circuit - Test

Usage:

3406E 1MM
System Operation Description:

Power train Data Links

Power train data links are designed to facilitate communication and control between electronically controlled Anti-Lock Brakes (ABS), traction control systems, transmissions, and engines. Typical control would include a momentary reduction of engine rpm and/or engine torque, that is triggered by a signal from an off-engine control module such as the ABS, the traction control, or the transmission. An off-engine control module is a control module that is not part of the Caterpillar engine control system.

Any combination of the following systems may be installed together on a vehicle:

  • Traction Control

  • Transmission Control

  • ABS

The required components are installed at the OEM when the vehicle is built.

Powertrain data link wiring, off-engine control modules, and wiring are installed by the vehicle OEM. Questions that are related to the hardware configuration, software, and installation should be directed to the vehicle OEM.

The following two power train data links are available:

  • SAE J1922

  • SAE J1939

The J1922 and J1939 refers to the standard for data link communications of the Society of Automotive Engineers Inc.. The ECM has a customer programmable parameter that is called "Powertrain Data Link" which can be programmed to any one of the following options:

  • J1922

  • J1939

  • J1922 and J1939

  • None

Anti-Lock Brake Systems (ABS)

The "Powertrain Data Link" may be used by an anti-lock brake system (ABS) in order to disable the engine retarder when the anti-lock brake control determines that the engine retarder should be disabled. This is usually achieved when the ABS system is active.

Traction Control Systems

Loss of traction is determined by sensors on the vehicle that are mounted near the wheels. These sensors are also used by the ABS system. Typically, a system with traction control includes Anti-Lock brakes.

Transmission Control

The following characteristics are determined by a vehicle speed sensor in the transmission:

  • Transmission shift points

  • Engine rpm

  • Load

The sensors for power train control provide signals to the vehicle control module of the "Powertrain Data Link". The vehicle control module of the "Powertrain Data Link" then communicates with the engine ECM. The engine ECM receives a request from the "Powertrain Data Link". The engine ECM responds by momentarily limiting the following characteristics:

  • Engine rpm

  • Torque

  • Both Engine rpm and Torque

The presence of an active J1922 data link circuit can be determined by observing the "Powertrain Status" screen on the Caterpillar Electronic Technician (Cat ET). The status screen will display "Installed" if the proper software is installed in the ECM, and there is no action that is being requested at that time by any of the control modules on the data link.

If an action is being requested by one of the vehicle control modules, the display will indicate the control that is making the request (Traction Control or Transmission Control) or a combination of the two (Traction Control and Transmission Control). Power train control is also displayed in the upper right hand corner of the display status screen. This space is replaced by the low oil pressure indicator, when a condition of low oil pressure exists.

J1922 Data Link

SAE J1922 is standard with all software.

Note: The J1922 data link wires are a twisted pair. The twisted pair is used to reduce electromagnetic interference. If a section of wiring must be replaced, the new wires should also be a twisted pair. Use care to maintain the polarity of the original wire when the pins and the sockets are being installed into the connectors.

J1939 Data Link

SAE J1939 is standard with all software.

Note: The wiring for the J1939 data link is a shielded twisted pair cable and the wiring is not serviceable. The wiring must be replaced when the wiring is damaged.




Illustration 1g00652190

Schematic for Power train data link




Illustration 2g00714306

ECM pin locations

Test Step 1. Inspect Electrical Connectors and Wiring

  1. Thoroughly inspect the J1/P1 ECM connector, the firewall bulkhead connector, the connectors for the power train control module, and the connector terminals for the SAE J1922 data link or the connector terminals for the J1939 data link. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

  1. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the SAE J1922 data link or the J1939 data link.

    Refer to Illustration 4.

  1. Check the ECM connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).

  1. Check the harness and wiring for abrasion and pinch points from the data link connectors back to the ECM.

Expected Result:

All connectors, pins, and sockets should be completely coupled and/or inserted and the harness and wiring should be free of corrosion, abrasion, or pinch points.

Results:

  • OK - Proceed to Test Step 2.

  • Not OK -

    Repair: Perform the following repair:Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.Verify that the repair eliminates the problem.

    STOP

Test Step 2. Check for Active Diagnostic Codes

  1. Connect Cat ET to the data link connector.

  1. Turn the key switch to the ON position.

  1. Monitor the active diagnostic code screen on Cat ET. Check and record active diagnostic codes.

Expected Result:

There is an active diagnostic code for the SAE J1922 data link or the SAE J1939 data link.

Note: The "Powertrain Data Link" parameter is a customer parameter that must not be programmed to J1939, or J1922 and J1939, unless the J1939 data link is being used.

Results:

  • J1939 - Proceed to Test Step 3.

  • J1922 - Proceed to Test Step 5.

  • Not OK - Proceed to Test Step 4.

Test Step 3. Check the Devices on the J1939 Data Link.

  1. Connect Cat ET to the data link connector.

  1. Access the special test "J1939 Receive Communication Status". The special tests are located under the Diagnostic menu.

  1. Cat ET will display the J1939 sources that have transmitted at least one good message that has been successfully received by the ECM. If the ECM has not received any messages from a source, that source will not be displayed. Examples of devices that can use the J1939 data link include the following switches:

    • Switches that are programmed to "Instrument Cluster"

    • Switches that are programmed to "Body Controller"

    • Switches that are programmed to "Cab Controller"

  1. Cat ET will display the J1939 source in the "Description" column. The "Status" column displays the status of the device.

  1. If an expected message is not received from a device, Cat ET will display "Not Receiving".

  1. The status screen on Cat ET can be set to display the status of a device that is not working. The status screen will display "No Comm" if a message is not received from the device.

Expected Result:

Cat ET displays the devices that are used on the vehicle and the ECM is receiving messages from the devices.

Results:

  • Yes - The ECM is receiving messages from the devices that are installed on the vehicle.STOP

  • No - The ECM is not receiving messages from the devices that are installed on the vehicle.

    Repair: The devices that can be programmed to use the J1939 data link can be circuits with two wires or circuits with three wires. Bad connections are the most frequent problem. Repair the suspect component or replace the suspect component. This may include the connectors, the wiring, and/or the device. Ensure that the connectors are free of corrosion.

    STOP

Test Step 4. Check the Power Train Status Screen




Illustration 3g00714416

Table 1
Powertrain Status Group Definition Table    
Heading On Status Screen     Displayed Message     Definition of Message    
Engine Speed         Actual Engine rpm of the engine    
Percent Torque         Current engine torque during operation that is expressed as a percent of peak torque    
Powertrain Status     "Not Installed", "ABS Control", "Traction Control", "Traction and ABS Control", "Trans Control", "Trans and ABS Control", "Trans and Traction Control", "Trans and Traction and ABS"     Communication of the Power Train control module    
TC Status or Transmission Status     "No Communication"     Communication from the vehicle control is not being received by the ECM. One of the following conditions exists: The vehicle does not support this feature. The vehicle control is not currently powered, or the wiring is damaged or disconnected.    
"Not Active" No requests from the Vehicle Power Train ECU (Electronic Control Unit)    
"Speed Command" Engine rpm is being controlled by a Vehicle ECU.    
"Torque Command" Engine torque is being controlled by a Vehicle ECU.    
"Speed and Torque Limit" Engine rpm and torque is being determined by a Vehicle ECU.    
"Torque Limit" The Torque limit is being determined by a Vehicle ECU.    
"Speed Limit" The rpm limit is being determined by a Vehicle ECU.    
TC Speed         The TC Speed is the desired engine rpm setpoint or the engine rpm limit that is being requested by the Vehicle's Traction Control ECU.    
TC Torque         The TC Torque is the desired percent of torque or the desired percent of torque limit that is being requested by the Vehicle's Traction Control ECU.    
Transmission Output Speed         The Transmission Output Speed is the desired engine rpm setpoint or the engine rpm limit that is being requested by the Vehicle's Traction Control ECU.    
Transmission Torque         The Transmission Torque is the desired percent of torque or the percent of torque limit that is being requested by the Vehicle's Traction Control ECU.    
ABS Status     "No Communication"     The ECM is not receiving communication from the vehicle's ABS/Traction Control System. One of the following conditions exists: The vehicle does not support this feature. The vehicle's ABS/Traction Control System is not currently powered. The wiring is damaged or disconnected.    
"Not Active" There are no requests from the ABS/Traction Control ECU.    
"Disable Retarder" This is a request from the ABS/Traction Control ECU to the ECM. The ABS/Traction Control System requests the disabling of the Engine Retarder operation.    

  1. Connect Cat ET to the data link connector.

  1. While the vehicle is being driven by someone else, monitor Cat ET. Use the following procedure:

    1. Access the status screen on Cat ET. Select the "Powertrain Status" screen. The "Powertrain Status" screen relates to the J1922 data link and J1939 data link.

    1. While the vehicle is being operated, monitor the "Powertrain Status" screen.

      Refer to Table 1 for an explanation of the headings that are displayed in the "Powertrain Status" screen on Cat ET.

      Note: Transmission shifts and/or a momentary loss of traction should trigger the appropriate action by the ECM when the correct sensors, controls and wiring are installed on the vehicle.

Expected Result:

The status screen indicates that the ECM is responding to a power train control.

Note: Some power train control modules have test modes that are available by activating diagnostic switches. Ensure that the Caterpillar ECM is not reacting to a test by the power train control module if the problem is related to power train control operation and you believe that the system should not be active.

Results:

  • OK - If the response is abnormal, send the vehicle to the OEM dealer for repairs.STOP

  • Not OK -

    Repair: Perform the following diagnostic procedure:Troubleshooting, "Troubleshooting without a Diagnostic Code"

    STOP

Test Step 5. Disconnect the Data Link Lines from the ECM Connector




Illustration 4g00652192

Terminal locations for ECM

  1. Turn the key switch to the OFF position.

  1. Remove the wires from J1/P1:14 (J1922 Data Link Negative) and J1/P1:1 (J1922 Data Link Positive). This may require disconnection of J1/P1 from the ECM.

  1. Reconnect vehicle harness connector P1 to the ECM when the wires are disconnected.

  1. Turn the key switch to the ON position.

  1. Monitor the active diagnostic code screen on Cat ET. Check and record active diagnostic codes.

Expected Result:

The following diagnostic code is active:

  • 249-11 J1922 Data Link Fault (58)

Note: If the J1922 data link is not being used for the vehicle's power train control, program the "Powertrain Data Link" parameter to "None". After the "Powertrain Data Link" parameter is programmed to "None", the following active diagnostic code should be repaired:

  • 249-11 J1922 Data Link Fault (58)

Results:

  • OK -

    Repair: Perform the following diagnostic procedure:

    1. Use the following procedure if the vehicle is not using the J1922 data link for power train control:

      1. Leave the pins for the data link disconnected from the ECM.

      1. Fill the unused cavities of connector P1 with Deutsch plugs.

      1. Program the parameter for the "Powertrain Data Link" to "None".

    1. Use the following procedure if the vehicle is using the J1922 data link for power train control:

      1. Temporarily connect a test ECM.

      1. Repeat the Test Step.

      1. If the problem is resolved with the test ECM, reconnect the suspect ECM.

      1. If the problem returns with the suspect ECM, replace the ECM.

    STOP

  • Not OK - The ECM is OK.

    Repair: Perform the following diagnostic procedure:

    1. Use the following procedure if the vehicle is not using the J1922 data link for power train control:

      1. Leave the pins of the data link disconnected from the ECM.

      1. Fill the unused cavities of connector P1 with Deutsch plugs.

      1. Program the parameter for the "Powertrain Data Link" to "OFF".

      1. Verify that the repair eliminates the problem.

    1. Use the following procedure if the vehicle is using the J1922 data link for power train control:

      1. Send the vehicle to the OEM dealer for repair.

      1. Verify that the repair eliminates the problem.

    STOP

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