G3500H Generator Set Engine Caterpillar

Data Link - Test

Usage:

Use this procedure to troubleshoot a problem with the data link. Also, use this procedure if one of following diagnostic codes is active or easily repeated.

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Table 1
J1939 Code and Description	Comments
51-9 Engine Throttle Position : Abnormal Update Rate	The ECM is not communicating properly with the throttle actuator over the CAN data link. The code is logged.
173-9 Engine Exhaust Gas Temperature : Abnormal Update Rate	The ECM is not communicating properly with the ISM over the Global CAN data link. The code is logged.
898-9 Engine Requested Speed/Speed Limit : Abnormal Update Rate	The "Desired Speed Input Configuration" must be set to "CAN" for the code to be set. The ECM is not communicating properly with the Operator Control Panel (OCP) over the CAN data link. The code is logged.
1442-9 Engine Fuel Valve #1 Position : Abnormal Update Rate	The ECM is not communicating properly with the fuel metering valve. The code is logged.
2241-9 Source Address 241 : Abnormal Update Rate⁽¹⁾	The ECM is not communicating properly with the ISM over the Local CAN data link. The code is logged.
2452-9 Generator Total Real Power : Abnormal Update Rate	The ECM is not receiving generator power sensor information from the EMCP. The code is logged.
3216-9 Aftertreatment #1 NOx : Abnormal Update Rate	The ECM is not communicating properly with the NOx sensor. The code is logged.
3542-9 Requested Engine Control Mode : Abnormal Update Rate	The "Engine State Control Input Configuration" must be set to "CAN" for the code to be set. The ECM is not communicating properly with the EMCP over the CAN data link. The code is logged.
3470-9 Engine Turbocharger Compressor Control : Abnormal Update Rate	The ECM is not communicating properly with the compressor bypass actuator over the CAN data link. The code is logged.

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⁽¹⁾	Integrated Sensing Module (ISM) data link

If Cat^® Electronic Technician (ET) will not communicate with the ECM, refer to Troubleshooting, "Electronic Service Tool Does Not Communicate" before you begin this procedure. The procedure will verify that electrical power is being supplied to the ECM and to the service tool connector.

The data links are used to communicate information between the engine ECM and other control modules that are a part of the application. Cat ET also communicates with the ECM via the data links.

The service tool connector contains connections for electrical power and for the data links.

Cat ET may display the following error message:

"The version of the ECM is not recognized and the integrity of the changed parameters and displayed data is not guaranteed."

This message indicates one of the following conditions:

The flash file in the ECM is newer than the version of Cat ET.
The latest version of Cat ET has not been installed.

-9 Detected Problems

Loss of device battery power or ground
Loss of device keyswitch power supply
An invalid configuration parameter
Software incompatibility between two or more ECM's on the network
Hardware incompatibility between CAN-based system components
Damaged CAN data link wiring
Missing or damage terminating resistors

NOx Sensor Power Supply Enablement Conditions

A Cat ET service test, for overriding the power supply may be available for diagnostic testing purposes. If an override is unavailable, starting and running the engine in accordance with the sensor buffer power-on requirements will be necessary.

The buffer is powered by the ECM after the following conditions are verified:

No diagnostic codes related to the NO_X sensor are active
Engine speed above 500 rpm
Engine accumulated run time duration up to 3 minutes to remove moisture from sensor.
The calculated power on delay time has expired.

An active diagnostic code is probably caused by a problem with a connector or harness for the CAN data link or the power supply. The next likely cause is a problem with the NO_X sensor group. The least likely cause is a problem with the ECM.

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Table 2
Component	Electrical Checkout
NOx Sensor	ET Service Test Override Parameter for the NOx sensor power supply

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Illustration 1	g06123547
For the complete circuit details, refer to the full schematic.

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Illustration 2	g06123566
For the complete circuit details, refer to the full schematic.

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Table 3
Troubleshooting Test Steps	Values	Results
1. Check for Codes A. Connect Cat^® Electronic Technician (ET) to the service tool connector. B. Determine if a code is active or logged.	Codes	Result: A -9 code is active or logged. Proceed to Test Step 2.
2. Check for Battery Voltage at the Affected Component A. Turn the power to the ON position. B. Measure the voltage between the following terminals on the wiring harness connector for the affected component: - Battery (+) and Battery (-) - Keyswitch Power (+) and Battery (-) NOx sensor specific information: If available, activate the Cat ET service override for the NOx sensor power supply. If unavailable, start the engine and run in accordance with NOx sensor power supply enablement conditions listed in the beginning of this procedure.	Battery Voltage	Result: Both of the following are true: - Battery voltage was measured between Battery (+) and Battery (-) - Battery voltage was measured between Keyswitch Power (+) and Battery (-) Proceed to Test Step 3. Result: Either of the following are true: - Battery voltage was not measured between Battery (+) and Battery (-) - Battery voltage was not measured between Keyswitch Power (+) and Battery (-) There is an open or a short in the wiring harness. There may be a problem with the keyswitch relay, or relay coil battery (+) or battery (-). Repair: Repair or replace the wiring harness or keyswitch relay. Proceed to Test Step 4.
3. Check the Termination Resistors for the J1939 Data Link A. Turn the main disconnect switch to the OFF position. B. At the affected component, measure the resistance between the following CAN data link terminals: - CAN (+) and CAN (-)	60 ± 10 Ohms	Result: The resistance is less than 50 Ohms. There are more than 2 termination resistors installed in the wiring harness or a short circuit has been detected. Repair: Repair or replace damaged components. Proceed to Test Step 4. Result: The resistance is 60 ± 10 Ohms. The termination resistors are OK. Proceed to Test Step 4. Result: The resistance is approximately 120 ± 10 Ohms. There is a problem with a termination resistor or a termination resistor is missing. Repair: Check the resistance on each terminating resistor. Replace the failed termination resistor. Proceed to Test Step 4. Result: The resistance is greater than 130 ohms. There is a problem with the wiring harness between the ECM and the next connection point in the data link wiring. Repair: Repair or replace the wiring harness. Proceed to Test Step 4.
4. Check for Active CAN Communication A. Connect Cat ET. B. Use Cat ET to monitor the following: - Codes	Codes	Result: A code is not active. Return to service. Result: A -9 diagnostic is still active and communication problems continue. There may be a problem with one of the communicating devices. If multiple devices show an active-9 diagnostic, and the wiring is correct, you may have a problem with the ECM. If only one device is showing an active -9 diagnostic, that specific device may have a problem. Contact your dealer TC for further assistance.

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).