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| Illustration 1 | g02703098 |
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Connections of the Cab Air Temperature Control switch | |
This diagnostic code is associated with the Cab Air Temperature Control switch. The FMI 04 diagnostic code means that the Brake ECM has determined that the voltage the signal circuit for the sensor is above normal.
Conditions that can cause this diagnostic code to be activated are listed below:
- The switch for the AC has failed.
- The AC switch is shorted to the +battery circuit
- The ECM has failed. An ECM failure is unlikely.
Before performing this procedure, inspect the harness connectors that are involved in the circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean, secure and in good condition. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure.
Note: Ensure that CID 2659 FMI 04 is active before performing this procedure.
Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear the diagnostic codes when problem has been corrected.
Note: Use a digital multimeter for the measurements in this procedure.
System Response:
- Air conditioning may not work properly.
- The Auto Temperature Control feature will not work properly.
Test Step 1. CHECK THE STATUS OF THE DIAGNOSTIC CODE
- Inspect the harness connectors. Clean the contacts for the harness connectors. Check all wires for damage from chafing, corrosion, or excessive heat.
- Perform a
45 N (10 lb) pull test on each of the wires that are associated with the sensor circuit. - Reconnect all harness connectors. Make sure that the connectors are fully seated and the clips for each connector are fastened.
- Turn the disconnect switch and the key start switch to the ON position.
- Operate the machine.
- Determine if the CID 2659 FMI 04 diagnostic code is active.
Expected Result:
The CID 2659 FMI 04 diagnostic code is active.
Results:
- YES - The CID 2659 FMI 04 diagnostic code is active. The diagnostic code has not been corrected. Proceed to Test Step 2.
- NO - The CID 2659 FMI 04 diagnostic code is not active. The diagnostic code does not exist at this time. The initial diagnostic code was probably caused by a poor connection or a short at one of the connectors that was disconnected and reconnected. Resume normal operation.
STOP
Test Step 2. CHECK THE SWITCH OPERATION
- Turn the disconnect switch and the key start switch to the OFF position.
- Disconnect the switch from the machine harness.
- Connect one lead of the multimeter to Contact 1 C540-GY(Grey)of the switch.
- Connect the other lead of the multimeter to Contact 2 299-BK(Black)of the switch.
- Operate the switch while checking for continuity from Contact 1 to Contact 2 of the switch.
- Move the multimeter lead from Contact 1 to Contact 3.
- Operate the switch while checking for continuity from Contact 3 to Contact 2 of the switch.
Expected Result:
Continuity exists from Contact 1 to Contact 2 only when the switch is in the ON position. Continuity does NOT exist from Contact 2 to Contact 3 only when the switch is in the ON position.
Results:
- OK - Continuity exists from Contact 1 to Contact 2 only when the switch is in the ON position. Continuity does NOT exist from Contact 2 to Contact 3 only when the switch is in the ON position. Proceed to Test Step 3.
- NOT OK - The switch does not operate properly. The switch has failed.
Repair: Replace the switch.
STOP
Test Step 3. CHECK FOR A SHORT TO GROUND
- The key start switch and the disconnect switch remain in the OFF position.
- The connector for the switch remains disconnected from the machine harness.
- Disconnect the machine harness connectors J1 and J2 from the ECM.
- At the J2 harness connector for the ECM, measure the resistance from Contact J2-61 C540-GY(Grey)frame ground.
- At the J2 harness connector for the ECM, measure the resistance from Contact J2-60 C539-YL(Yellow)to frame ground.
Expected Result:
Each resistance measurement is greater than 5000 ohms.
Results:
- YES - Each resistance measurement is greater than 5000 ohms. The circuit is not shorted to ground. The ECM may have failed.
Repair: An ECM failure is unlikely. Exit this procedure and perform this procedure again. Prior to replacing an ECM, always contact the Technical Communicator for your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the ECM requires replacement, see Troubleshooting, "Electronic Control Module (ECM) - Replace".
STOP
- NO - A resistance measurement is less than 5000 ohms. There is a short to ground in the machine harness.
Repair: The switch circuit C540-GY(Grey)or C539-YL(Yellow)is shorted to a ground source. Refer to the complete Electrical System Schematic of the machine. Examine all connections in the circuit for a short to ground. Check for locations of contact of the machine harness with the machine frame. Repair the machine harness or replace the machine harness.
STOP