This procedure checks the switch circuits that can affect the speed of the engine. The following switches are covered by this procedure:
- Neutral switch
- Service brake pedal position switch 1
- Service brake pedal position switch 2
- Clutch pedal position switch
- Fast idle enable switch
- Cruise control on/off switch
- Cruise control set/resume switch
Note: Refer to Troubleshooting, "Speed Control (PTO) - Test" in order to check the circuits for the Power Take-Off (PTO).
Programming the Inputs
Each input must be programmed to the correct terminal of the P1 connector on the Engine Control Module (ECM) in order for the ECM to respond to the input. Illustration 1 lists the programming options that are available. Use the Caterpillar Electronic Technician (ET) to determine the programming of the inputs.
Refer to Troubleshooting, "Programmable Input Parameters" for additional information about the parameters.
Two different types of input configurations are available:
Hard Wired - The switch is wired directly to an input terminal on the P1 connector. The switch connects the input terminal to the return or to the +Battery.
J1939 Data Link - The switch is wired to a vehicle control module. The vehicle control module transmits the status of the switch to the engine ECM via the J1939 data link.
The following components can cause problems with a switch circuit:
- Electrical connector or wiring
- Switch
- Vehicle control module
- Engine ECM
In most cases, an open circuit in an electrical connector or the wiring is the root cause of the problem. The least likely cause is a problem with a module.
Diagnostics on the Caterpillar Electronic Technician (ET)
Wiggle Test - The wiggle test allows you to monitor the input while you wiggle the wiring. This helps to identify faulty electrical connections.
For additional information regarding the wiggle test, refer to the documentation that accompanies your Cat ET software.
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| Illustration 1 | g01297984 |
Typical example of the switch circuits | |
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| Illustration 2 | g01297986 |
P1 terminals for programming the inputs | |
Test Step 1. Determine the Vehicle's Configuration
Determine the configuration of the wiring for the switch.
Expected Result:
The switch is wired directly to the ECM.
Results:
- Hard wired - Proceed to Test Step 2.
- J1939 Data Link -
Repair: If there are other problems with the J1939 data link, refer to Troubleshooting, "Link - Test".If there are no other problems with the J1939 data link, the problem is with one of the following components:
- Wiring between the switch and the vehicle control module
- Switch
- Fuse or circuit breaker
STOP
- Wiring between the switch and the vehicle control module
Test Step 2. Perform the Wiggle Test
Carefully following this procedure is a good way to identify the root cause of intermittent problems.
- Interview the operator. Determine if there are other electrical problems. If there are other electrical problems, there is a problem with the battery or with the wiring between the battery and the fuse or the circuit breaker.
Check the wiring between the battery and the fuse or the circuit breaker. Continue with this procedure if there is only one indication of an electrical problem.
- Verify that the engine is OFF and that the keyswitch is ON.
- Configure Cat ET for the wiggle test. Select the status group that includes the appropriate parameter. Start the wiggle test.
- Slowly wiggle the wiring harness and the connectors between the P1 connector and the switch. Pay particular attention to the wiring near each connector. Be sure to wiggle all of the wiring between the P1 connector and the switch.
As you wiggle the wiring, observe the harness and the connectors. Look for these problems:
- Loose connectors or damaged connectors
- Damage that is caused by excessive heat
- Damage that is caused by chafing
- Improper routing of wiring harnesses
- Damaged insulation
- Loose connectors or damaged connectors
- Slowly wiggle the wiring between the switch and the fuse or the circuit breaker, if necessary. Pay particular attention to the wiring near each connector.
Expected Result:
The wiring failed the wiggle test.
Results:
- The wiring failed the wiggle test. -
Repair: Repair the wiring, when possible. Replace parts, if necessary. Send the vehicle to the OEM dealer for repair, if necessary. Verify that the problem is resolved.
STOP
- The wiring passed the wiggle test. -
Repair: There may be a problem with the switch. Perform the following procedure:
- Verify that the connectors for the switch are securely fastened. Verify that the wiring to the connector is in good condition. Repair any problems, when possible. Continue with this procedure, if necessary.
- Disconnect the connector for the switch. Carefully inspect the terminals in each connector for proper installation. Repair any problems, when possible. Continue with this procedure, if necessary.
- Measure the resistance across the switch's terminals when the switch is activated and when the switch is not activated.
The resistance must be less than five Ohms when the switch is closed. The resistance must be an open circuit when the switch is open.
Repair any problems, when possible. Replace parts, if necessary. Send the vehicle to the OEM dealer for repair, if necessary. Verify that the problem is resolved.
STOP