Use this procedure in order to troubleshoot the Engine Control Switch (ECS) or use this procedure if the diagnostic code in Table 1 is active or easily repeated.
| Diagnostic Codes Table | ||
|---|---|---|
| Description | Conditions which Generate this Code | System Response |
| 336-2 Engine Control Switch erratic, intermittent, or incorrect | The two inputs from the ECS are in the opposite state. | The code is logged. |
The 336-2 diagnostic code is generated when the two start/run/stop inputs to the Engine Control Module (ECM) are not complementary. The status for the Engine Control Switch will display "Abnormal/Incorrect Data" while the fault is active.
The Electronic Modular Control Panel 3 (EMCP 3) controls the starting and stopping of the engine. The engine parameters for the total number of crank cycles and the engine cooldown must be programmed to zero (0).
The following inputs for the engine control are located on the panel for the EMCP 3: "RUN", "AUTO" and "STOP". These switches control a primary input and a secondary input to the ECM. The primary input to the ECM is over the J1939 data link. The secondary input is a set of relay contacts in the EMCP 3 that are normally open to digital return. If the primary input is lost the ECM will look to the secondary input. The engine parameter for the secondary input must be set to the enabled state in order for the secondary input to be recognized. When the "RUN" switch is pushed on the panel for the EMCP 3 the start/run/stop inputs 1 and 2 to the ECM are pulled low.
If the signals to the start/run/stop input of the ECM are in opposite states, the ECM determines that one of the signals is faulty. When this happens the ECM will keep the last good input. When the diagnostic code activates and the switch is in the "STOP" position, the engine will not start. When the diagnostic activates and the switch is in the "RUN" position, the engine will continue to run.
Note: For the troubleshooting of applications that are equipped with an EMCP 3, refer to Systems Operation, Troubleshooting, Testing and Adjusting, RENR7902.
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| Illustration 1 | g01205508 |
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Schematic for the ECS with EMCP 3 | |
Test Step 1. Check for Connector Damage.
- Set the EMCP 3 to the STOP position.
- Turn the battery disconnect switch to the OFF position.
- Thoroughly inspect the ECM connectors J1/P1 and J2/P2. Inspect all of the other connectors. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.
- Perform a
45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit. - Check the allen head screw on each ECM connector for the proper torque. Refer to Troubleshooting, "Inspecting Electrical Connectors" for the correct torque values.
- Check the harness and the wiring for abrasion and for pinch points.
Expected Result:
All connectors, pins, and sockets are completely coupled and/or inserted, and the harness and wiring are free of corrosion, of abrasion and of pinch points.
Results:
- OK - The connectors and wiring are okay. Proceed to Test Step 2.
- Not OK - The connectors and/or wiring are not okay.
Repair: Repair the connectors and/or wiring or replace the connectors and/or wiring.
STOP
Test Step 2. Check for a CID-FMI.
- Connect the Caterpillar Electronic Technician (ET).
- Turn the battery disconnect switch to the ON position.
- Set the EMCP 3 to the STOP position.
- Observe the logged diagnostic codes on Cat ET.
- Observe the status screen on Cat ET.
Expected Result:
Cat ET indicates a CID-FMI 336-2.
Results:
- OK - Cat ET indicates a CID-FMI 336-2. Proceed to Test Step 3.
- Not OK - Cat ET does not indicate a CID-FMI 336-2.
Repair: The problem may be intermittent. If the problem is intermittent, perform the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".
STOP
Test Step 3. Check the Wiring for an Open Condition
- Turn the EMCP 3 to the STOP position.
- Turn the battery disconnect switch to the OFF position.
- Disconnect the J1/P1 ECM connector.
- Check for continuity between P1-22 start/run/stop 2 and P1-21 start/run/stop 1 with a resistance measurement.
Expected Result:
A short circuit condition exists.
Results:
- OK - A short circuit condition exists. Proceed to Test Step 4.
- Not OK - A short circuit condition does not exist between P1-22 and P1-21.
Repair: There is an open circuit between P1-22 and P1-21. Repair the wires or replace the wires between P1-22 and P1-21. Verify that the problem has been resolved.
STOP
Test Step 4. Check ECM For Proper Operation
- Remove the wire F716 from P1-21. Install a jumper wire with a socket terminal into PA-21.
- Remove the wire F716 from P1-22. Install a jumper wire with a socket terminal into P1-22.
- Remove the wire E998 from P2-66. Install a jumper wire with a socket terminal into P2-66.
- Connect the three jumper wires together.
- Turn the battery disconnect switch to the ON position.
Expected Result:
The status for the Engine Control Switch is Run. The active 336-2 is gone.
Results:
- OK - The status for the Engine Control Switch is Run. The active 336-2 is gone.
Repair: There may be an intermittent problem. If the problem is intermittent, perform the diagnostic functional testTroubleshooting, "Inspecting Electrical Connectors".
STOP
- Not OK - The status for the Engine Control Switch is "Abnormal/Incorrect Data". The 336-2 code is active.
Repair: Replace the ECM. Refer to the diagnostic procedure Troubleshooting, "Replacing the ECM".
STOP