G3306B Petroleum Generator Set Engines Caterpillar


CAN Data Link - Test

Usage:

G3306B NR4
Use this procedure to troubleshoot the CAN data link circuit if a problem is suspected. Also use this procedure if one of the diagnostic codes in Table 1 are active or easily repeated.

Table 1
Diagnostic Codes Table    
Description     Conditions which Generate this Code     System Response    
51-9 Engine Throttle Position : Abnormal Update Rate     The Electronic Control Module (ECM) did not receive the required message from the throttle actuator.     The code is logged.
The amber warning lamp is illuminated.
The red stop lamp is illuminated.    
1442-9 Engine Fuel Valve 1 Position : Abnormal Update Rate     The ECM did not receive the required message from the throttle actuator.     The code is logged.
The amber warning lamp is illuminated.
The red stop lamp is illuminated.    
3542-9 Requested Engine Control Mode : Abnormal Update Rate     The parameter for Engine State Control Input Configuration is set to "CAN Input".
The ECM did not receive the required message from the engine control switch.    
The code is logged.
The amber warning lamp is illuminated.
The red stop lamp is illuminated.
The engine is shut down.    



Illustration 1g01930194



Illustration 2g03430433

Locations of the components that are on the CAN data link

(1) Throttle actuator

(2) Fuel actuator

(3) ECM

(4) Display panel




Illustration 3g01940214

Location of the connectors at the ECM (right front engine view)

(5) J1/P1 ECM connectors for the fuel control solenoid

(6) Service tool connector that is on the engine

(7) Connector for the interconnect harness

(8) Termination resistor




Illustration 4g01931773

Terminal locations at the P1 ECM connector that are associated with the CAN data link

(P1-20) CAN data link +

(P1-21) CAN data link −

(P1-22) CAN shield




Illustration 5g01940634

Terminal locations for the CAN data link at the fuel actuator

(Terminal 4) CAN data link +

(Terminal 6) CAN data link −




Illustration 6g01940869

Terminal locations for the CAN data link at the fuel actuator

(Terminal 4) CAN data link +

(Terminal 6) CAN data link −




Illustration 7g01940516

Terminal locations for the CAN data link at the fuel actuator

(Terminal 4) CAN data link +

(Terminal 6) CAN data link −




Illustration 8g01940394

Terminal locations at the connector for the interconnect harness for the CAN data link

(P8-F) CAN data link +

(P8-L) CAN data link −

(P8-V) CAN shield




Illustration 9g01940416

Terminal locations at the connector for the interconnect harness for the CAN data link

(P8-F) CAN data link +

(P8-L) CAN data link −

(P8-V) CAN shield




Illustration 10g01707176

Terminal locations at the connector for the interconnect harness for the CAN data link

(P8-F) CAN data link +

(P8-L) CAN data link −

(P8-V) CAN shield

The CAN data link is used for communication between the following modules: the engine ECM, customer devices, and various display modules. Two 120 Ohm terminating resistors must be installed in the wiring harness in order for the CAN data link to function properly.

Table 2
Troubleshooting Test Steps     Values     Results    

1. Inspect the Electrical Connectors and the Wiring

A. Remove electrical power from the ECM.

B. Thoroughly inspect the electrical connectors for the CAN data link circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the proper procedure for inspecting the connectors and the wiring.
   

Electrical Connections    

Results: The connectors and wiring appear to be OK.

Proceed to Test Step 2.

Result: There is a problem in the connectors and/or wiring.

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 coupled.

Verify that the repair eliminated the problem.    

2. Verify the Proper Installation of the Terminating Resistors

A. Verify that the terminating resistors are installed at the ends of the data link.

B. Disconnect the J1/P1 connector and measure the resistance between P1-20 (CAN data link +) and P1-21 (CAN data link -).    

60 ± 3 Ohms    

Results: The resistance is within the range.

Repair: The termination resistors are OK. The data link appears to be OK. The problem is probably an intermittent problem in a connector or in the harness. If the problem persists, perform this procedure again. If an intermittent problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect" for information that is related to troubleshooting intermittent electrical problems.

Proceed to Test Step 3.

Results: The resistance is approximately 120 Ohms. There is a problem with a termination resistor.

Repair: Determine the cause of the missing termination resistor. Repair the problem, when possible. Replace parts, if necessary.
Verify that the repair eliminated the problem.
   

3. Check for Shorts in the Harness

A. Disconnect the J1/P1 ECM connector at the ECM.

B. Disconnect any control modules from the CAN data link.

C. Disconnect Cat ET from the service tool connector.

D. Measure the resistance from the P1-20 terminal to every terminal on ECM connectors P1 and P2.

E. Measure the resistance from P1-20 to the chassis ground.

F. Measure the resistance from P1-21 to every terminal on ECM connectors P1 and P2.

G. Measure the resistance from P1-21 to the chassis ground.
   

Open Circuit    

Results: Each measurement indicates an open circuit. The wiring for the data link does not have a short circuit.

Proceed to Test Step 4.

Results: The resistance measurements do not indicate an open circuit.

Repair: Repair the connectors or wiring and/or replace the connectors or wiring.

STOP    

4. Check for an Open in the Harness

A. Connect a jumper wire between terminals P1-20 and P1-21.

B. Measure the resistance between terminals 3 (CAN data link +) and 2 (CAN data link - ) at the customer connector.

C. Measure the resistance at the connectors of any other control modules.
   

Short Circuit    

Results: The resistance measurement indicates a short circuit. The CAN data link is OK.

Repair: If the problem is intermittent, refer to Troubleshooting, "Inspecting Electrical Connectors".

STOP

Results: The resistance measurement does not indicate a short circuit. There is an open circuit in the harness of connectors.

Repair: Repair the connectors or wiring and/or replace the connectors or wiring.
   

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