0335756 JOHNSON PLATE, Rear

Table 1
J1939 Codes and Description Comments
1656-2
Engine Automatic Start Enable Switch : Erratic, Intermittent, or Incorrect The two inputs from the Engine Control Switch (ECS) are in the opposite state.
The code is logged.
Illustration 1 g06494419
For the complete circuit details, refer to the full schematic.
Table 2
Troubleshooting Test Steps Values Results
1. Inspect the Electrical Connectors and the Wiring
A. Turn the main disconnect switch to the OFF position.
B. Thoroughly inspect the connectors. Refer to Troubleshooting, "Electrical Connectors-Inspect" for additional information.
C. Perform a 45 N (10 lb) pull test on the connector wires.
D. Check the harness for abrasions and pinch points.
Connectors and Wiring
Result: The connectors and wiring appear to be OK.
Proceed to Test Step 2.
Result: There is a problem with the connectors and/or wiring.
Repair: Repair or replace the connectors or wiring. Ensure that all the seals are properly in place and ensure that the connectors are coupled.
If the problem is not resolved, proceed to Test Step 2.
2. Check the Status of the Switch Position
A. Connect the Cat® Electronic Technician (Cat ET) Service Tool to the service tool connector.
B. Use Cat ET to monitor the status of the following switch:
- Start/Run/Stop switch
C. Turn the Start/Run/Stop switch to the following positions:
- STOP position
- START position
- STOP position
Switch Status
Result: The parameter for the switch is not correct in either the STOP or the START positions.
Proceed to Test Step 3.
Result: The status for the switch is correct in both the START and STOP positions. A code for the switch is not active.
Repair: The switch appears to be operating correctly. There may be an intermittent problem in the wiring harness or connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for additional information.
If the problem is not resolved, proceed to Test Step 3.
3. Check the Wiring for an Open Circuit
A. Turn the main disconnect switch to the OFF position.
B. Disconnect the wiring harness from the Electronic Control Module (ECM) and Engine Interface Connector (EIC).
C. Measure the resistance between the following ECM and EIC connector terminals:
- ECM connector L-C1 terminal 40 and EIC connector C-C2 terminal 46.
- ECM connector L-C1 terminal 54 and EIC connector C-C2 terminal 47.
Open Circuit
Result: Both measurements were less than 10 ohms between the connector terminals.
Proceed to Test Step 4.
Result: One or more of the measurements were greater than 10 ohms between the connector terminals.
Repair: An open circuit has been detected. Repair or replace the wiring harness.
If the problem is not resolved, proceed to Test Step 4.
4. Check the Wiring for a Short Circuit to Engine Ground
A. Turn the main disconnect switch to the OFF position.
B. Disconnect the wiring harness from the ECM and EIC.
C. Measure the resistance between the following ECM and EIC connector terminals:
- The affected Engine Control Switch (ECS) signal wire pin and Engine ground
Short Circuit
Result: Both measurements were greater than 100 K ohms between a throttle actuator connector terminal and engine ground.
Proceed to Test Step 5.
Result: One or more of the measurements were less than 100 K ohms between a throttle actuator connector terminal and engine ground.
Repair: There is a short circuit in the wiring harness. Repair or replace the wiring harness.
If the problem is not resolved, proceed to Test Step 5.
5. Check the Wiring Harness for a Pin to Pin Short Circuit
A. Turn the main disconnect switch to the OFF position.
B. Disconnect the wiring harness from the ECM.
C. Measure the resistance between the following ECM connector terminals:
- The affected ECS signal wire pin and all other pins in the ECM connector.
Short Circuit
Result: One or more of the measurements were less than 100 K ohms between a connector terminals and any other terminal in the ECM connector.
Repair: There is a short circuit in the wiring harness. Repair or replace the wiring harness.
Result: All measurements were greater than 100 K ohms between the affected ECS signal wire pin and all other pins in the ECM connector.
Repair: The problem is located outside the Caterpillar system wiring circuit. Refer to Customer system schematics or instruction for additional information.
Verify that the repair eliminated the problem.
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).