PISTON GP 4933287 - Caterpillar

Use this procedure if a problem is suspected with the circuit for customer installed automatic start switch. Also use this procedure if the diagnostic code in Table 1 is active or easily repeated.
Table 1
Diagnostic Codes Table
J1939 Code and Description Conditions which Generate this Code System Response
1656-2 Automatic Start Enable Switch : Erratic, Intermittent, or Incorrect The Electronic Control Module (ECM) detects a parity error in the circuit for the customer installed switch. The Engine State Control Input Configuration parameter must be set to "Hardwired Input" for this code to become active. The code is logged..
The red stop lamp is illuminated.
The engine is shut down.
The ECM is latched. For this application, the customer may install an engine control switch that can be used for automatic engine starting and stopping from a remote location. In order for the switch inputs to be read by the ECM, the Engine State Control Input Configuration parameter must be set to "Hardwired Input". Two switch inputs at the ECM are used to detect the following circuit signals:
Table 2
Customer Installed Automatic Start Switch States
ECM Function P1-40 P1-54
Engine Auto Start Grounded Grounded
1656-2 Active Open Grounded
1656-2 Active Grounded Open
Engine Auto Stop Open Open The most likely problem with the automatic start function is probably caused by a problem with the customer installed switch. The next likely cause is a problem in the harness or in a connector. The least likely cause is a problem with the ECM.
Illustration 1 g02725898
Schematic for the automatic start circuit
Test Step 1. Inspect the Electrical Connectors and the Wiring
Remove the electrical power from the engine.
Thoroughly inspect the condition of the J1/P1 ECM connectors and the engine interface connectors. Also, thoroughly inspect the customer installed wiring from the engine interface connector to the customer installed switch. Refer to Testing and Adjusting, "Electrical Connectors - Inspect" for the correct procedure.
Check the torque of the fasteners for each of the ECM connectors and of the engine interface connector. Refer to Testing and Adjusting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness inside the ECM control panel and the wiring for abrasion and for pinch points from the ECM to the engine interface connector. Expected Result:All connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points.Results:
OK - The connectors, wiring, and the circuit breaker appear to be OK. Proceed to Test Step 2.
Not OK - The connectors, wiring, or the circuit breaker are not OK.Repair: Repair the problem. Replace parts, if necessary. Verify that the repair has eliminated the original problem.STOPTest Step 2. Install a Jumper at the Engine Interface Connector and Check the Engine State Control
Remove the electrical power from the engine.
Use a wire removal tool to remove the wires from terminal locations 46 and 47 at the engine interface connector.
Connect the Caterpillar Electronic Technician (ET) to the service tool connector.
Restore the electrical power to the engine.
Observe the status of the Engine Operating State status parameter. The Engine Operating State of the engine will