System Operation Description:
Use this procedure under the following situation:
Use this procedure to determine if the “Service Brake Pedal Position (Switch 2)” is preventing normal operation of the cruise control, the idle set speed or the PTO.
“Service Brake Pedal Position (Switch 2)”
The “Service Brake Pedal Position (Switch 2)” is required when the “Transmission Style” parameter is programmed to Automatic Option 2 or Automatic Option 3. This switch has an identical function as “Service Brake Pedal Position (Switch 1)”. This switch is used only when a redundant system is required. Unlike the “Service Brake Pedal Position (Switch 1)”, this switch connects to + Battery. This provides a fully redundant system. A logged fault will be present if the status of the two brake switches do not agree. This switch is used to exit cruise control, Cab Switch PTO mode or idle. The switch may also be used to override the idle shutdown timer during the last 90 seconds. This capability is determined by the following customer parameter:
• “Allow Idle Shutdown Override”
Refer to Troubleshooting, “Service Brake Pedal Position (Switch 1) Circuit – Test” for more details on the operation of the brake pedal position switches.
A. Thoroughly inspect ECM vehicle harness connector J1/P1 and the firewall bulkhead connector.
Refer to Troubleshooting, “ Electrical Connectors – Inspect” for details.
B. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the switches.
Refer to Illustration 173.
C. Check the ECM connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).
D. Check the harness and wiring for abrasion and pinch points from the sensor to the ECM.
Expected Result:
All connectors, pins, and sockets should be completely coupled and/or inserted and the harness and wiring should be free of corrosion, abrasion, or pinch points.
Results:
• OK – Proceed to Test Step 2.
• Not OK
Repair: Perform the following repair:
Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.
Verify that the repair eliminates the problem.
STOP.
Test Step 2. Check the Switch Status on ET
A. Access the status screen on the Caterpillar Electronic Technician (ET).
B. Turn the ignition key switch to the ON position.
C. Start the engine or ensure that the air system is charged if the vehicle is equipped with air brakes.
D. Depress the Service Brake while the status of both brake switches is being observed on ET.
E. Release the service brake while the status of both brake switches is being observed on ET.
Note: If the Service Brake Pedal Position (Switch 2) status indicates “Not Installed”, check the programming of the “Transmission Style” parameter. The “Transmission Style” must be programmed to Automatic Option 2 or Automatic Option 3 if a second switch is used.
Expected Result:
The switch status changes per the information in table 154
Results:
• OK – The switch is operating normally.
Repair: Perform the following diagnostic
procedure:
Troubleshooting, “Service Brake Pedal Position (Switch 1) Circuit – Test”.
STOP.
• Not OK – The ECM is not reading the switch status change. Proceed to Test Step 3.
Test Step 3. Check the Switch Circuit of the ECM
A. Turn the ignition key switch to the OFF position.
B. Fabricate a jumper wire 100 mm (4 inch) long.
Crimp a Deutsch pin to both ends of the wire.
C. Disconnect vehicle harness connector P1 from the ECM.
D. Connect a 70-Termial Breakout T to ECM connector J1 and connect P1 to the breakout T.
E. Install the jumper wire into terminal 52 (un switched +Battery) of the breakout T. Connect the other end of the jumper wire to (terminal 64) which is the Service Brake Pedal Position (Switch 2) of the breakout T.
F. Turn the ignition key switch to the ON position.
G. Connect ET to the cab data link connector.
H. Access the status screen on ET.
I. While the status of the Service Brake Pedal Position (Switch 2) is being monitored on the status screen, slowly remove the jumper from terminal 52 and slowly insert the jumper from terminal 52.
Expected Result:
The switch status changes per the information in table 155
Results:
• OK – The ECM is functioning properly. Proceed to Test Step 4.
• Not OK – The ECM is not functioning properly.
Repair: Perform the following repair:
1. Temporarily connect a test ECM.
2. Remove all jumpers and replace all connectors.
3. Recheck the system for active diagnostic codes.
4. Repeat the Test Step.
5. If the problem is resolved with the test ECM, reconnect the suspect ECM.
6. If the problem returns with the suspect ECM, replace the ECM.
7. Verify that the repair eliminates the problem.
STOP.
Test Step 4. Insert a Jumper at the Service Brake Pedal Position (Switch 2)
A. Turn the ignition key switch to the OFF position.
B. Ensure that ECM vehicle harness connector J1/P1 is connected.
C. Find the switch in the vehicle.
D. Disconnect the wires from the switch terminals.
E. Turn the ignition key switch to the ON position.
F. Connect ET to the cab data link connector.
G. Access the status screen on ET.
H. While the switch status is being monitored on the status screen slowly connect the suspect switch wires and slowly disconnect the suspect switch wires.
Expected Result:
Refer to table 156.
Results:
• OK
Repair: Perform the following repair:
Replace the faulty switch. Verify that the repair eliminates the problem.
STOP.
• Not OK – There is a problem in the harness between the switch and the ECM. Proceed to Test Step 5.
Test Step 5. Insert a Jumper at the Bulkhead Connector
A. Turn the ignition key switch to the OFF position.
B. Fabricate a jumper wire 100 mm (4 inch) long.
Crimp a Deutsch pin to both ends of the wires.
C. Find the switch terminal in the engine side of the bulkhead connector for the vehicle harness. Also, find a convenient location for + Battery voltage.
D. Insert the jumper wire between the two terminals in the engine side of the bulkhead connector.
E. Turn the ignition key switch to the ON position.
F. Connect ET to the cab data link connector.
G. Access the status screen on ET.
H. While the switch status is being monitored on the status screen alternately remove the jumper wire from the + Battery connection, and alternately install the jumper wire at the + Battery connection.
Expected Result:
Refer to table 157.
Results:
• OK – The problem is in the vehicle wiring between the bulkhead connector and the switch.
Repair: Perform the following repair:
Inspect the vehicle wiring and repair the vehicle wiring, as required. If the problem still exists with the wiring, send the vehicle to the OEM dealer.
STOP.
• Not OK – The problem is in the vehicle wiring between the bulkhead connector and the ECM.
Repair: Perform the following repair:
Inspect the vehicle wiring and repair the vehicle wiring, as required. If the problem still exists with the wiring, send the vehicle to the OEM dealer.
STOP.