C175 Tier 4 Final Engines for Off-Highway Trucks Caterpillar

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

Table 1

J1939 Code and Description	CDL Code and Description	Comments
N/A	296-9 Transmission Control Module : Abnormal Update Rate	The code is logged. The check engine lamp is illuminated. The ECM has lost all communication to the transmission control module over the Cat Data Link.
N/A	296-14 Transmission Control Module : Special Instruction	The code is logged. The check engine lamp is illuminated. The ECM has lost all communication to the transmission control module over the Cat Data Link.
N/A	533-9 Brake Control Module : Abnormal Update Rate	The code is logged. The check engine lamp is illuminated. The ECM has lost all communication to the brake control module over the Cat Data Link.
N/A	533-14 Brake Control Module : Special Instruction	The code is logged. The check engine lamp is illuminated. The ECM has lost all communication to the brake control module over the Cat Data Link.
N/A	1273-9 Chassis Control Module : Abnormal Update Rate	The code is logged. The check engine lamp is illuminated. The ECM has lost all communication to the chassis control module over the Cat Data Link.
N/A	1273-14 Chassis Control Module : Special Instruction	The code is logged. The check engine lamp is illuminated. The ECM has lost all communication to the chassis control module over the Cat Data Link.
N/A	3050-9 Drivetrain Control : Abnormal Update Rate	Troubleshooting, "Data Link - Test"
639-9 J1939 Network #1 : Abnormal Update Rate	247-9 SAE J1939 Data Link : Abnormal Update Rate	Communication has been lost to one of the devices on the datalink. If multiple devices are not communicating, there is likely a problem with the datalink.
639-14 J1939 Network #1 : Special Instruction	247-14 SAE J1939 Data Link : Special Instruction	The affected Electronic Control Module (ECM) is missing expected parameters.
1231-9 J1939 Network #2 : Abnormal Update Rate	2348-9 SAE J1939 Data Link #2 : Abnormal Update Rate	Communication has been lost to one of the devices on the datalink. If multiple devices are not communicating, there is likely a problem with the datalink.
1231-14 J1939 Network #2 : Special Instruction	2348-14 SAE J1939 Data Link #2 : Special Instruction	The affected ECM is missing expected parameters.
1235-9 J1939 Network #3 : Abnormal Update Rate	5856-9 SAE J1939 Data Link #3 : Abnormal Update Rate	Communication has been lost to one of the devices on the datalink. If multiple devices are not communicating, there is likely a problem with the datalink.
1235-14 J1939 Network #3 : Special Instruction	5856-14 SAE J1939 Data Link #3 : Special Instruction	The affected ECM is missing expected parameters.
2853-9 Communications Connection : Abnormal Update Rate	N/A	Communication has been lost to one of the devices on the datalink. If multiple devices are not communicating, there is likely a problem with the datalink.
3360-9 Aftertreatment #1 DEF Controller : Abnormal Update Rate	3820-9 Aftertreatment #1 Diesel Exhaust Fluid Controller : Abnormal Update Rate	The #1 Diesel Exhaust Fluid Control Unit (DCU) triggered a CAN communication diagnostic code and shutdown the SCR system.
3360–14 Aftertreatment #1 DEF Controller : Special Instruction	3820-14 Aftertreatment #1 Diesel Exhaust Fluid Controller : Special Instruction	The #1 DCU triggered a CAN communication diagnostic code and shutdown the SCR system.
4450-9 Aftertreatment #2 DEF Controller : Abnormal Update Rate	4577-9 Aftertreatment #2 DEF Controller #1 : Abnormal Update Rate	The #3 Diesel Exhaust Fluid Control Unit (DCU) triggered a CAN communication diagnostic code and shutdown the SCR system.
4450-14 Aftertreatment #2 DEF Controller : Special Instruction	4577-14 Aftertreatment #2 DEF Controller #1 : Special Instruction	The #3 DCU triggered a CAN communication diagnostic code and shutdown the SCR system.
7538-9 Aftertreatment #1 DEF Controller #2 : Abnormal Update Rate	4797-9 Aftertreatment #1 Diesel Exhaust Fluid Controller #2 : Abnormal Update Rate	The #2 DCU triggered a CAN communication diagnostic code and shutdown the SCR system.
7538-14 Aftertreatment #1 DEF Controller #2 : Special Instruction	4797-14 Aftertreatment #1 Diesel Exhaust Fluid Controller : Special Instruction	The #2 DCU triggered a CAN communication diagnostic code and shutdown the SCR system.

Table 2

Associated Codes
J1939 Code	CDL Code	Troubleshooting Procedure
5965-5	3838-5	Troubleshooting, Solenoid Valve - Test (Aftertreatment)
5965-6	3838-6	Troubleshooting, Solenoid Valve - Test (Aftertreatment)
5966-6	3965-6	Troubleshooting, Solenoid Valve - Test (Aftertreatment)
7602-2	5028-2	Troubleshooting, Diesel Exhaust Fluid Controller Resistor - Test
7602-3	5028-3	Troubleshooting, Diesel Exhaust Fluid Controller Resistor - Test
7602-4	5028-4	Troubleshooting, Diesel Exhaust Fluid Controller Resistor - Test
7603-2	5029-2	Troubleshooting, Diesel Exhaust Fluid Controller Resistor - Test
7603-3	5029-3	Troubleshooting, Diesel Exhaust Fluid Controller Resistor - Test
7603-4	5029-4	Troubleshooting, Diesel Exhaust Fluid Controller Resistor - Test

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

The "System Communication Status" is located under the diagnostics tab in Cat ET. Click the "System Communication Status" option. Once the screen opens up, the information will automatically be loaded from the ECM. If there is an issue with the datalink and the datalink is repaired, the "Load from ECM" button will have to be clicked again to see the updated status. If there are communication issues between multiple modules, each module can be selected individually to determine which components are having communication issues. If the problem is intermittent, the "View History" button can be clicked to see all the communication faults that have previously logged.

Table 3

Cat ET Diagnostic Code Cross Reference to Wiring Schematic
Code Description	Data Link	Devices on Network
J1939 Network #1	Can A	Engine ECM and Machine ECMs
J1939 Network #2	Can B	Engine ECM to Selective Catalyst Reduction Controller Engine ECM to Fuel Control Valve
J1939 Network #3	Can C	Selective Catalyst Reduction Controller to Diesel Exhaust Control Units and NOx sensors

Table 4

Required Tools		Qty
372-5260	Test Kit	1

Illustration 1	g06080139

Illustration 2	g06080804

Table 5

Troubleshooting Test Steps	Values	Results
1. Check for Codes A. Connect Cat® ET to the service tool connector. B. Look for active codes that are associated with the system for the diagnostic code.	Codes	Result: An associated code is active. Repair: Troubleshoot the associated code before continuing with this test. Result: An associated code is not active or logged. Proceed to Test Step 2.
2. Check for Codes A. Connect Cat ET. B. Determine if a code is active or logged.	Codes	Result: A -9 code is active or logged. Proceed to Test Step 6. Result: A -14 code is active or logged. Proceed to Test Step 3.
3. Check the Part Number of the Component A. Locate the part number of the component that was identified by the "System Communication Status". B. Check to see if the part number is correct for the application.	Part Number	Result: The part number is correct for the application. Proceed to Test Step 4. Result: The part number is incorrect for the application. Repair: Replace the component with the correct part number. Refer to Special Instruction, REHS8151 for special handling instructions if replacing a NOx sensor. Proceed to Test Step 16.
4. Check for Incorrect Configuration Parameters A. Connect Cat ET. B. Identify the component that logged the -14 code. C. Use Cat ET to verify that the correct parameters are being used.	Parameters	Result: The parameters are correct. Proceed to Test Step 5. Result: The parameters are not correct. Repair: Input the correct parameters. Refer to Troubleshooting, Configuration Parameters, for additional information. If the problem is not resolved, proceed to Test Step 5.
5. Ensure that the latest Flash File Software is Installed in the ECM A. Connect Cat ET. B. Use Cat ET to verify that the correct flash file is being used.	Flash File	Result: The flash file is correct for the application. Repair: A failed component has been identified. Replace the failed component. Proceed to Test Step 16. Result: The flash file is incorrect for the application. Repair: Reflash the component to the correct flash file. Proceed to Test Step 16.

Illustration 3	g03846524

Illustration 4	g03846007

Table 6

6. Use the "System Communication Status" to Determine the Communication Issue A. Connect Cat ET. A. Use Cat ET to verify that Device 1 and Device 2 are present in the "Device's" column (1) within "System Communication Status" screen. B. Verify that Device 1 and Device 2 are present "System Communication Status".	Component Identified	Result: Device 1 and Device 2 are present. Record the devices identified as Device 1 and Device 2 in column 1. Proceed to Test Step 7. Result: Only Device 1 is present. Record the device identified as Device 1 in column 1. Proceed to Test Step 14.
7. Check the Resistance of the Datalink A. Turn the keyswitch to OFF. B. Measure the resistance of the data link between the following Device 2 wiring harness connector terminals: - +Data link and -Data link Note: If Device 2 is the Aftertreatment Diesel Exhaust Fluid Controller (DCU), the 398-5063 Probe must be used to prevent damage to the DCU connector.	60+/-10 Ohms	Result: The resistance is less than 50 Ohms. There are more than 2 terminating resistors installed in the wiring harness or a short circuit has been detected. Repair: Repair or replace damaged components. Proceed to Test Step 17. Result: The resistance is 60 ±10 Ohms. The termination resistors are OK. Proceed to Test Step 8. If the component identified as device 2 is the fuel control valve, proceed to Test Step 16. Result: The resistance is 120 ±10 Ohms. There is a problem with a terminating resistor. Repair: Check the resistance on each terminating resistor. Replace the failed terminating resistor. Proceed to Test Step 17. Result: The resistance is greater than 130 Ohms. There is a problem with both terminating resistors or an open circuit has been detected. Repair: Determine the cause of the problem. Repair or replace damaged components. Proceed to Test Step 17.
8. Check the Power and Ground to Device 2 A. Turn the keyswitch to ON. B. Measure the voltage between the following Device 2 wiring harness connector terminals: - +Battery and -Battery Note: If Device 2 is the DCU, the 398-5063 Probe must be used to prevent damage to the DCU connector.	Battery Voltage	Result: The voltage is equal to battery voltage and Device 2 is the DCU. Proceed to Test Step 9. Result: The voltage is equal to battery voltage and Device 2 is not the DCU. Repair: Replace the component identified as Device 2. Refer to Special Instruction, REHS8151 for special handling instructions if replacing a NOx sensor. Proceed to Test Step 17. Result: The voltage is not equal to battery voltage and device 2 is the DCU. There is an open or short in the wiring circuit. Proceed to Test Step 9.
9. Check the Resistance of the Diesel Exhaust Fluid Control Unit (DCU) Resistor A. Turn the keyswitch to OFF. B. Disconnect the 86-pin connector from the DCU that is logging the code. C. Measure the resistance between pin-38 and pin-39 on the DCU that is logging the code: - For Aftertreatment #1 DCU #1 the resistance should measure 178Ω ± 10Ω. - For Aftertreatment #1 DCU #2 the resistance should measure 604Ω ± 10Ω. - For Aftertreatment #2 DCU #1 the resistance should measure 1540Ω ± 10Ω. - For Aftertreatment #2 DCU #2 the resistance should measure 5230Ω ± 10Ω. Note: The 398-5063 Probe must be used to prevent damage to the DCU connector.	Resistance	Result:The resistance measurement of the DCU resistor at the affected DCU was within specification. Proceed to Test Step 15. Result: The resistance measurement of the DCU resistor at the affected DCU was not within specification. Proceed to Test Step 10.
10. Check the Resistance of the DCU Resistor A. Turn the keyswitch to OFF. B. Disconnect the 8-pin connector from the DCU resistor. C. Measure the resistance between the following pins: - For Aftertreatment #1 DCU #1, pin-1 and pin-5, the resistance should measure 178Ω ± 10Ω. - For Aftertreatment #1 DCU #2, pin-2 and pin-6, the resistance should measure 604Ω ± 10Ω. - For Aftertreatment #2 DCU #1, pin-3 and pin-7, the resistance should measure 1540Ω ± 10Ω. - For Aftertreatment #2 DCU #2, pin-4 and pin-8, the resistance should measure 5230Ω ± 10Ω. Note: The 398-5063 Probe must be used to prevent damage to the DCU connector.	Resistance	Result:The resistance measurement of the DCU resistor was within specification. Proceed to Test Step 11. Result: The resistance measurement of the DCU resistor was not within specification. Repair: A failed DCU resistor has been detected. Replace the DCU resistor. Proceed to Test Step 17.
11. Check the Wiring between the DCU Resistor and the Affected DCU for an Open Circuit A. Turn the keyswitch to OFF. B. Disconnect the 86-pin connector from the affected DCU. C. Disconnect the 8-pin connector from the DCU resistor. D. Measure the resistance between the following pins: - For Aftertreatment #1 DCU #,1, pin-38 on the DCU 86-pin connector and pin-1 on the DCU resistor 8-pin connector. - For Aftertreatment #1 DCU #,1, pin-39 on the DCU 86-pin connector and pin-5 on the DCU resistor 8-pin connector. - For Aftertreatment #1 DCU #2, pin-38 on the DCU 86-pin connector and pin-2 on the DCU resistor 8-pin connector. - For Aftertreatment #1 DCU #2, pin-39 on the DCU 86-pin connector and pin-6 on the DCU resistor 8-pin connector. - For Aftertreatment #2 DCU #1, pin-38 on the DCU 86-pin connector and pin-3 on the DCU resistor 8-pin connector. - For Aftertreatment #2 DCU #1, pin-39 on the DCU 86-pin connector and pin-7 on the DCU resistor 8-pin connector. - For Aftertreatment #2 DCU #2, pin-38 on the DCU 86-pin connector and pin-4 on the DCU resistor 8-pin connector. - For Aftertreatment #2 DCU #2, pin-39 on the DCU 86-pin connector and pin-8 on the DCU resistor 8-pin connector. Note: The 398-5063 Probe must be used to prevent damage to the DCU connector.	Resistance	Result: There were less than 10 Ohms of resistance between all the pins on the affected DCU and the DCU resistor. Proceed to Test Step 12. Result: There were more than 12 Ohms of resistance between all the pins on the affected DCU and the DCU resistor. Repair: An open circuit has been detected. Replace the wiring harness. Proceed to Test Step 17.
12. Check the Wiring between the DCU Resistor and the Affected DCU for a Short Circuit A. Turn the keyswitch to OFF. B. Disconnect the 86-pin connector from the affected DCU. C. Disconnect the 8-pin connector from the DCU resistor. D. Measure the resistance between the following pins: - For Aftertreatment #1 DCU #1, pin-1 on the DCU resistor 8-pin connector and a known good ground. - For Aftertreatment #1 DCU #1, pin-5 on the DCU resistor 8-pin connector and a known good ground. - For Aftertreatment #1 DCU #2, pin-2 on the DCU resistor 8-pin connector and a known good ground. - For Aftertreatment #1 DCU #2, pin-6 on the DCU resistor 8-pin connector and a known good ground. - For Aftertreatment #2 DCU #1, pin-3 on the DCU resistor 8-pin connector and a known good ground. - For Aftertreatment #2 DCU #1, pin-7 on the DCU resistor 8-pin connector and a known good ground. - For Aftertreatment #2 DCU #2, pin-4 on the DCU resistor 8-pin connector and a known good ground. - For Aftertreatment #2 DCU #2, pin-8 on the DCU resistor 8-pin connector and a known good ground. Note: The 398-5063 Probe must be used to prevent damage to the DCU connector.	Resistance	Result:There were more than 100 K Ohms of resistance between all the pins on the affected DCU and the DCU resistor. Proceed to Test Step 13. Result:There were less than 100 K Ohms of resistance between all the pins on the affected DCU and the DCU resistor. Repair: A short circuit has been detected. Replace the wiring harness. Proceed to Test Step 17.
13. Check the Wiring between the DCU Resistor and the Affected DCU for a Pin to Pin Short Circuit A. Turn the keyswitch to OFF. B. Disconnect the 86-pin connector from the affected DCU. C. Disconnect the 8-pin connector from the DCU resistor. D. Measure the resistance between the following pins on the affected DCU: - Pin-38 on the DCU 86-pin connector and all other pins in the DCU wiring harness connector. - Pin-39 on the DCU 86-pin connector and all other pins in the DCU wiring harness connector. Note: The 398-5063 Probe must be used to prevent damage to the DCU connector.	Resistance	Result:There were more than 100 K Ohms of resistance between all the pins on the affected DCU wiring harness connector. Proceed to Test Step 15. Result:There were less than 100 K Ohms of resistance between all the pins on the affected DCU wiring harness connector. Repair: A short circuit has been detected. Replace the wiring harness. Proceed to Test Step 17.
14. Check the Resistance of the Datalink A. Turn the keyswitch to OFF. B. Measure the resistance of the Device 1 data link between the following Device 1 wiring harness connector terminals: - +Data link and -Data link Note: For the Aftertreatment Diesel Exhaust Fluid Controller (DCU), the 398-5063 Probe must be used to prevent damage to the DCU connector.	Resistance	Result: The resistance is less than 50 Ohms. There are more than 2 terminating resistors installed in the wiring harness or a short circuit has been detected. Repair: Repair or replace damaged components. Proceed to Test Step 17. Result: The resistance is 60 ±10 Ohms. The termination resistors are OK. Check the power, ground, and keyswitch (if applicable) supply to each module on the affected data link. Refer to the appropriate wiring diagram. Note: Keyswitch must be ON when checking the power supply. Repair: Repair the power and ground supply to the modules. Proceed to Test Step 17. Result: The resistance is 120 ±10 Ohms. There is a problem with a terminating resistor. Repair: Check the resistance on each terminating resistor. Replace the failed terminating resistor. Proceed to Test Step 17. Result: The resistance is greater than 130 Ohms. There is a problem with the wiring harness between Device 1 and the splice point into the data link wiring. Refer to the appropriate wiring diagram. Repair: Determine the cause of the problem. Repair or replace damaged components. Verify that the repair eliminated the problem.
15. Check the Keyswitch Circuit to the DCU A. Turn the keyswitch to OFF. B. Disconnect the 53-pin connector from the affected DCU. C. Turn the keyswitch to the ON position. D. Measure the voltage between the following: - Keyswitch power (Pin 52) and a known good ground Note: The 398-5063 Probe must be used to prevent damage to the DCU connector.	Battery Voltage	Result: The voltage is equal to battery voltage. Repair: Replace the DCU. Proceed to Test Step 17. Result: The voltage is not equal to battery voltage. Repair: There is an open circuit or a short circuit in the keyswitch wiring circuit. Repair or replace the wiring circuit. Refer to Troubleshooting, "DEF Control Module Power - Test" for additional information. Proceed to Test Step 17.
16. Check Power and Ground at the Fuel Control Valve (FCV) A. Turn the keyswitch to ON. B. Measure the voltage between the following terminals: - Terminal 1 and Terminal 5 on the fuel control valve wiring harness connector. - Terminal 8 and Terminal 5 on the fuel control valve wiring harness connector.	Battery Voltage	Result: The battery voltage is not equal to battery voltage. Repair: There is a problem with the power supply to the fuel control valve. Repair or replace damaged components. Proceed to Test Step 17. Result: The battery voltage is equal to battery voltage. Repair: Replace the fuel control valve. Proceed to Test Step 17.
17. Use the "System Communication Status" to Determine the Communication Issue A. Connect Cat ET. B. Perform the following diagnostic test: - "System Communication Status" C. Click the "Load from ECM" button to determine if any devices are not communicating.	Component Identified	Result: The "System Communication Status" does not show any communication issues. Return to service.

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).