019-428   Engine Datalinks

General Information

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The engine data link consists of circuitry located in the engine wiring harness. On older engines, the engine data link circuitry supports J1587/J1708 protocol. On newer engines, the engine data link circuitry supports J1939 protocol.

The purpose of the engine data link is to provide an access point for a service tool, such as INSITE™ electronic service tool, to communicate with the engine ECM. A service tool can communicate with the ECM on the engine data link free from data link traffic from other electronic devices that can be present on the OEM data link.

SAE J1939 Backbone Harness Overview:

SAE J1939 has strict guidelines that must be followed for successful communication. Understanding some fundamentals about SAE J1939 will help make sure these guidelines are followed.

The main component of an SAE J1939 system is a backbone harness. The harness can be up to 40 m [131 ft] long. The backbone harness is terminated at each end with 120 ohm resistors.

A maximum of 30 different devices can be attached to the SAE J1939 backbone at once. Each device, such as the data link adapter, is connected to the backbone through a stub which can be up to 1 m [3.2 ft] in length. The stub connector is a 3-pin plug.

 
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The terminating resistor caps (1) must be in place on the OEM backbone harness plugs (2) to maintain proper communication. Each resistor is 120 ohms and is located in a removable cap. This resistance is required when communicating with INSITE™ electronic service tool over the J1939 data link.

 
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Some engine harnesses, such as the QSK19 CM850 engine harness, include a complete SAE J1939 backbone harness. If this is supplied, connection to INSITE™ electronic service tool is accomplished either by a 9-pin data link connector (1), Part Number 3162848, or a 3-pin receptacle (2), Part Number 3162847.

To check for the J1939 backbone, turn the keyswitch to the OFF position. Measure the resistance from the SAE J1939 data link positive (+) pin to the SAE J1939 data link negative (-) pin of the 3-pin Deutsch™ connector.

The multimeter will show 60 ohms when the engine harness has provided a backbone on the data link bus.

 
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If the engine harness does not supply the J1939 backbone harness and the data link connector is a 3-pin receptacle, a mini-backbone harness will have to be added.

 
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Engine Data Link Connectors

The engine data link connector available on the engine harness will depend upon the data link circuitry in the engine harness and the vintage of the engine. Engine data link connectors available on Cummins® engines are summarized in the table below.

Connector Type
Data Link Protocols Supported
2-pin Weather Pack™
J1587/J1708
3-pin Deutsch™
J1939
6-pin Deutsch™
J1587/J1708
9-pin Deutsch™
J1587/J1708, J1939
 
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Each connector type is described in more detail in the following information.

The 9-pin Deutsch™ connector, Part Number 3824018, connector can supply SAE J1587/SAE 1708 and SAE J1939 communications, and battery voltage. The following are pin-outs for the 9-pin connector:

Pin
Signal
A
Ground
B
Unswitched Battery
C
J1939 data link (+)
D
J1939 data link (-)
E
J1939 data link (shield) (not applicable for Marine)
F
J1708 data link (+)
G
J1708 data link (-)
H
Open
J
Open
 
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The 6-pin Deutsch™ connector, Part Number 3824805, is found on some engines. This connector supplies SAE J1587/J1708, as well as the battery voltage. The following are pin-outs for the 6-pin connector:

Pin
Signal
A
J1708 data link (+)
B
J1708 data link (-)
C
Unswitched battery (+)
D
Open
E
Ground
F
Open
 
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NOTE: For CELECT Plus™ engines, do not use the in-cab 6-pin data link connector to calibrate the ECM. Use the data link connector found on the engine.

 
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The 3-pin SAE J1939 Deutsch™ connectors are also found on some Cummins® engine harnesses. Two possible types of 3-pin connectors can be present: A 3-pin plug (1), Part Number 3824288; and a 3-pin receptacle (2), Part Number 3284290. The following are the pin-outs for the 3-pin connector:

Pin
Signal
A
J1939 data link (+)
B
J1939 data link (-)
C
J1939 data link (shield)

The 3-pin connector only supports the SAE J1939 data link.

To meet the SAE J1939 standard, the 3-pin receptacle connector must be within 0.66 m [2.16 ft] of the ECM. Use of the J1939 mini-backbone harness, Part Number 3163096; may be required for proper termination resistance. The mini-backbone harness is required when no backbone is provided on the data link. Gender changer cable, Part Number 3163597, may be required to connect the mini-backbone harness to the engine harness or service tool cable.

NOTE: If there is 60 ohm resistance measured between pins A and B of the 3-pin connector, a backbone is on the data link.

On an ISB (except in a Dodge Ram™ pickup truck), an ISC, or an ISL engine, the 3-pin receptacle connector is located approximately six inches from the ECM.

On an ISB in a Dodge Ram™ pickup truck, the 3-pin plug connector is located near the fuel pump on the front gear housing.

On an ISM or ISX engine (prior to October 2002) the 3-pin receptacle is an OEM option. If the OEM has supplied a 3-pin receptacle connector, Part Number 3824290, for communications, it will be located in the OEM harness within 0.66 m [2.16 ft] of the ECM.

On an ISM or ISX engine (after October 2002) the 3-pin receptacle is located on the cold side of the engine.

On B Gas PLus, B LPG Plus, and C Gas Plus engines, the 3-pin SAE J1939 Deutsch™ receptacle, Part Number 3284290 is located near the OEM interface connectors. This connector is the OEM connection point for SAE J1939 devices and can also be used for INSITE™ electronic service tool communication. A mini-backbone harness, Part Number 3163096, is required for direct INSITE™ electronic service tool communication.

 
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The 2-pin connector is on many older engines, and only supplies SAE J1587/J1708 support (no battery voltage supply). The following are the pin-outs for the 2-pin connector:

Pin
Signal
A
J1587/J1708 data link (+)
B
J1587/1708 data link (-)
 
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Some engines have a 2-pin service tool power supply Weather Pack™ receptacle located in the engine harness. It can be used to power up any service tool device.

Pin
Signal
A
Unswitched battery (+)
B
Ground (-)
 
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Resistance Check

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 WARNING 

Batteries can emit explosive gases. To reduce the possibility of personal injury, always ventilate the compartment before servicing the batteries. To reduce the possibility of arcing, remove the negative (-) battery cable first and attach the negative (-) battery cable last.
 CAUTION 

For the J1939 engine data link, use test lead, Part Number 3822758, on the ECM connector to avoid damage to the connector pins. Use test lead, Part Number 3824811, for the 9-pin Deutsch™ connector. Use test lead, Part Number 3823993 for the 3-pin Deutsch™ connector pin receptacle or test lead, Part Number 3823994 for the 3-pin Deutsch™ connector.
 CAUTION 

For the J1587/J1708 engine data link, use test lead, Part Number 3622758, on the ECM connector to reduce the possibility of damage to the connector pins. Use test lead 3824800 for the 6-pin Deutsch™ connector. Use test lead 3823995 for the 2-pin Packard™ connector.

Determine the type of engine data link available on the engine, either J1939 or J1587/J1708. Follow the instructions provided to measure the resistance for the type of engine data link identified.

 
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J1939 Engine Data Link

  • Disconnect the batteries.
  • Disconnect the engine harness connector from the ECM. Turn the keyswitch to the OFF position.
 
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Insert a test led into the SAE J1939 data link positive (+) pin of the engine harness ECM connector, and connect it to the multimeter probe. Insert the other test lead into the SAE J1939 data link positive (+) pin of the 3-pin or 9-pin Deutsch™ connector, and connect it to the multimeter.

Measure the resistance. The multimeter must show a closed circuit (10 ohms or less).

If the circuit is not closed, repair or replace the engine harness.

See the Troubleshooting and Repair manual for additional information.

 
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Insert the multimeter lead into the SAE J1939 data link negative (-) of the engine harness ECM connector. Touch the other lead to the SAE J1939 data link negative (-) pin of the 3-pin or 9-pin Deutsch™ connector. Measure the resistance. The multimeter must show a closed circuit (10 ohms or less).

If the circuit is not closed, repair or replace the engine harness.

See the Troubleshooting and Repair manual for additional information.

 
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If the values are correct, the circuit must still be checked for a short circuit to ground and a short circuit from pin-to-pin.

Remove the lead from the SAE J1939 data link negative (-) pin of the engine harness ECM connector and insert it into the SAE J1939 data link (shield) pin. Touch the negative multimeter lead to the SAE J1939 data link (shield) pin of the 3-pin or 9-pin Deutsch™ connector. Measure the resistance.

The multimeter must show a closed circuit (10 ohms or less). If more than 10 ohms are measured in any of these steps, there could be a open circuit in the SAE J1939 data link (shield) pin, the SAE J1939 data link negative (-) pin, or the SAE J1939 data link positive (+) pin, or the polarity is not correct.

 
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J1587/J1708 Engine Data Link

Turn the keyswitch to the OFF position. Disconnect the engine harness from the ECM.

Insert a test lead into the SAE J1587 data link positive (+) pin of the engine harness ECM connector and connect it to a multimeter probe. Insert the other test lead into the SAE J1587 data link positive (+) pin of the 2-pin or 6-pin connector and connect it to the other multimeter probe. Measure the resistance. The multimeter must show a closed circuit (10 ohms or less).

If the circuit is not closed, repair or replace the engine harness.

See the Troubleshooting and Repair manual for additional information.

 
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Remove the test lead from the SAE J1587 data link positive (+) pin and insert it into the SAE J1587 data link negative (-) pin of the ECM connector. Remove the other test lead from the SAE J1587 data link positive (+) pin and insert it into the SAE J1587 data link negative (-) pin of the 2-pin or 6-pin connector. Measure the resistance. The multimeter must show a closed circuit (10 ohms or less).

If the circuit is not closed, repair or replace the engine harness.

See the Troubleshooting and Repair manual for additional information.

 
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Remove the test lead from the SAE J1587 data link negative (-) pin and insert it into the battery negative (-) pin of the 6-pin Deutsch™ connector. Remove the test lead from the SAE J1587 data link negative (-) pin of the engine connector and disconnect it from the multimeter probe. Touch the multimeter probe to the engine block ground. Measure the resistance. The multimeter should show a closed circuit (10 ohms or less).

If the circuit is not closed, repair or replace the engine harness.

See the Troubleshooting and Repair manual for additional information.

 
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 WARNING 

Batteries can emit explosive gases. To reduce the possibility of personal injury, always ventilate the compartment before servicing the batteries. To reduce the possibility of arcing, remove the negative (-) battery cable first and attach the negative (-) battery cable last.
 CAUTION 

Use test lead, Part Number 3824811, for the 6-pin Deutsch™ connector.

Disconnect the batteries.

Measure the resistance from the positive (+) battery terminal to battery positive (+) of the 6-pin Deutsch™ connector. The multimeter must show a closed circuit (10 ohms or less).

If the circuit is not closed repair or replace the engine harness.

See the Troubleshooting and Repair manual for additional information.

If the values are correct, the circuit must still be checked for a short circuit to ground and a short circuit from pin-to-pin.

 
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Check for Short Circuit to Ground

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 CAUTION 

For the J1939 engine data link, use test lead, Part Number 3822758, on the ECM connector to avoid damage to the connector pins.
 CAUTION 

For the J1587/J1708 engine data link, use test lead, Part Number 3822758, on the ECM connector to avoid damage to the connector pins.

Determine the type of engine data link available on the engine, either J1939 or J1587/J1708. Follow the instructions provided for short circuit to ground check for the type of engine data link identified.

J1939 Engine Data Link

Disconnect the engine harness connector from the ECM. Insert a test lead into SAE J1939 data link positive (+) pin of the engine harness ECM connector and connect it to a multimeter probe. Touch the other multimeter probe to engine block ground.

Measure the resistance. The multimeter must show an open circuit (100k ohms or more).

If the circuit is not open, repair or replace the engine harness.

See the Troubleshooting and Repair manual for additional information.

 
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Remove the test lead from the SAE J1939 data link positive (+) pin and insert it into the SAE J1939 data link negative (-) pin of the ECM connector. Measure the resistance from the SAE J1939 data link negative (-) pin of the engine harness ECM connector to the engine block ground. The multimeter must show an open circuit (100k ohms or more).

If the circuit is not open, repair or replace the engine harness.

See the Troubleshooting and Repair manual for additional information.

If less than 100k ohms is measured in any of the previous steps, there is a short to circuit to ground. Repair or replace the engine harness.

See the Troubleshooting and Repair manual for additional information.

 
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J1587/J1708 Engine Data Link

Disconnect the engine harness connector from the ECM.

Insert a test lead into the SAE J1587 data link positive (+) pin of the engine harness ECM connector and connect it to a multimeter probe. Touch the other multimeter probe to the engine block ground. Measure the resistance. The multimeter must show an open circuit (100k ohms or more).

If the circuit is not open, repair or replace the engine harness.

See the Troubleshooting and Repair manual for additional information.

 
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Remove the test lead from the SAE J1587 data link positive (+) pin and insert it into the SAE J1587 data link negative (-) pin of the engine harness ECM connector. Touch the other multimeter probe to the engine block ground. Measure the resistance from the SAE J1587 data link negative (-) pin of the engine harness ECM connector to the engine block ground. The multimeter must show an open circuit (100k ohms or more).

If the circuit is not open, repair or replace the engine harness.

See the Troubleshooting and Repair manual for additional information.

 
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Check for Short Circuit from Pin to Pin

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 CAUTION 

For the J1939 engine data link, use test lead, Part Number 3822758, on the ECM connector to avoid damage to the connector pins.
 CAUTION 

For the J1587/J1708 engine data link, use test lead, Part Number 3822758, on the ECM connector to avoid damage to the connector pins.

J1939 Engine Data Link

Disconnect the engine harness connector from the ECM.

Insert a test lead into the SAE J1939 data link positive (+) pin of the engine harness ECM connector and connect it to the multimeter probe. Insert the other test lead into another pin in the connector of the engine harness ECM connector and connect it to the other multimeter probe.

Measure the resistance from the SAE J1939 data link positive (+) pin to the first pin in the connector. The multimeter must show an open circuit (100k ohms or more).

If the circuit is not open, repair or replace the engine harness.

See the Troubleshooting and Repair manual for additional information.

 
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Remove the lead from the first pin in the connector and measure the resistance from the SAE J1939 data link positive (+) pin of the engine harness ECM connector to all other pins in the connector, one at a time. The multimeter must show an open circuit (100k ohms or more) at all pins.

If the circuit is not open, repair or replace the engine harness.

See the Troubleshooting and Repair manual for additional information.

 
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Remove the test lead from the J1939 data link positive (+) pin and insert it into the J1939 data link (shield) pin of the engine harness ECM connector. Insert the other test lead into another pin in the connector. Measure the resistance.

The multimeter must show an open circuit (100k ohms or more).

If the circuit is not open, repair or replace the engine harness.

See the Troubleshooting and Repair manual for additional information.

Measure the resistance from the SAE J1939 data link (shield) pin to all other pins in the connector, one at a time. The multimeter must show an open circuit (100k ohms or more).

If the circuit is not open, repair or replace the engine harness.

See the Troubleshooting and Repair manual for additional information.

 
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Remove the test lead from the SAE J1939 data link (shield) pin and insert it into the SAE J1939 data link negative (-) pin of the engine harness ECM connector. Insert the other test lead into another pin in the connector. Measure the resistance.

The multimeter must show an open circuit (100k ohms or more).

If the circuit is not open, repair or replace the engine harness.

See the Troubleshooting and Repair manual for additional information.

Measure the resistance from the SAE J1939 data link negative (-) pin of the engine harness connector to all other pins in the connector, one at a time. The multimeter must show an open circuit (100k ohms or more).

If the circuit is not open, repair or replace the engine harness.

See the Troubleshooting and Repair manual for additional information.

 
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J1587/J1708 Engine Data Link

Disconnect the engine harness connector from the ECM.

Insert a test lead into the SAE J1587 data link positive (+) pin of the engine harness ECM connector and connect it to the multimeter probe. Insert the other test lead into another multimeter probe. Measure the resistance. The multimeter must show an open circuit (100k ohms or more).

If the circuit is not open, repair or replace the engine harness.

See the Troubleshooting and Repair manual for additional information.

 
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Remove the lead from the first pin in the connector and test all other pins in the connector. Measure the resistance from the SAE J1587 data link positive (+) pin of the engine harness ECM connector to all other pins in the connector, one at a time. The multimeter must show an open circuit (100k ohms or more).

Remove the test lead from the SAE J1587 data link positive (+) pin of the engine harness ECM connector and insert it into the SAE J1587 data link negative (-) pin.

Measure the resistance from the SAE J1587 data link negative (-) pin to all other pins in the connector. The multimeter must show an open circuit (100k ohms or more) at all pins.

If the circuit is not open, repair or replace the engine harness.

See the Troubleshooting and Repair manual for additional information.

 
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Last Modified:  08-Jul-2010

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