PIPE A.-EXH. 8F8353 - Caterpillar

Illustration 1 g02788946
Schematic of the Service Brake Pedal SwitchThis diagnostic code is recorded when the status of the service brake pedal switch is wrong. The switch closes the circuit between the battery and the secondary brake solenoid when the service brake pedal is fully pressed. A diagnostic code is recorded when the ECM detects an open circuit and the switch is near the floor. The possible causes of this diagnostic code are listed below:
The Signal circuit (G731-GY) is open or shorted.
+Battery wire (198-RD) is open.
The switch is not adjusted correctly.
The switch has failed.
The ECM has failed. ECM failure is unlikely. System Response:The diagnostic code causes the backup circuit for the engagement of the brakes from the service brake pedal to malfunction. The service brake will continue to operate correctly. Note: A diagnostic code for the service brake pedal position sensor (CID 0468) can affect the status of CID 0298 FMI 02. Also, check for a problem with the electrical system (CID 0168). Check for any diagnostic codes for the secondary brake solenoid (CID 0722). Clear CID 0168 diagnostic code, CID 0468 diagnostic code, or CID 0722 diagnostic code before you proceed. Note: The status of the service brake pedal switch is updated only when the brake pedal is pressed. In order to determine the status of the switch, turn the key start switch to the ON position while the brake pedal is released. Then, press the brake pedal completely. Use this same procedure in order to clear the diagnostic code after repairs have been made. Test Step 1. CHECK THE BATTERY VOLTAGE FOR THE SWITCH.
Turn the key start switch to the ON position.
Disconnect the machine harness from the connector of the switch.
At the machine harness, measure the voltage between contact 1 and frame ground. Expected Result:The voltage should be greater than 22 VDC.Results:
OK - The voltage is greater than 22 VDC. Proceed to Test Step 2.
NOT OK - The voltage is not greater than 22 VDC.Repair: There is an open circuit or there is a short circuit. Check the fuse for the dump valve. Check for an open circuit or short circuit in wire (198-RD) from the fuse for the dump valve to the switch. Repair the cause of the open circuit or the short circuitSTOPTest Step 2. CHECK THE SIGNAL CIRCUIT FOR A SHORT TO GROUND.
The machine harness remains disconnected from the switch.
Turn the key start switch to the OFF position.
Disconnect the machine harness from the secondary brake solenoid.
Disconnect the machine harness connectors J1 and J2 from the ECM.
At machine harness connector J1 and J2, measure the resistance from contact J2-5 (solenoid signal) to all possible sources of ground.Expected Result:Each resistance should be greater than 5000 ohms. Results:
OK - Each resistance is greater than 5000 ohms. The machine harness is not shorted to ground. Proceed to Test Step 3.
NOT OK - Each resistance is not greater than 5000 ohms. Repair: There is a short in the machine harness. The short is between the signal circuit for