FO4326 Force BODY CHANNEL WELCH PLUG

Illustration 1 g00770278
SchematicTest Step 1. Inspect Electrical Connectors and Wiring
Turn the keyswitch to the OFF/RESET position.
Thoroughly inspect ECM connector J1/P1, ECM connector J2/P2, machine connector J3/P3, and all other connectors in the wiring harness. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.Expected Result:All connectors, pins, and sockets are completely inserted and coupled. The harness and wiring are free of corrosion, of abrasion, and of pinch points. All connections and grounds are tight and free of corrosion.Results:
OK - Proceed to Test Step 2.
Not OK - Repair: Repair the circuit.Verify that the repair eliminates the problem.STOPTest Step 2. Check the Sensor Supply Voltage at the Sensor Connector
Disconnect the suspect sensor.
Turn the keyswitch to the ON position.
Use a multimeter to measure the voltage across terminal A (+5V Analog) and terminal B (Analog Return) at the harness side of the suspect sensor connector.
Turn the keyswitch to the OFF/RESET position.Expected Result:The analog sensor supply voltage is 5.0 0.5 VDC.Results:
OK - The supply voltage is reaching the sensor. Proceed to Test Step 3.
Not OK - The supply voltage is not reaching the sensor.Repair: Refer to Troubleshooting, "Analog Sensor Supply Circuit - Test" for the appropriate troubleshooting procedure.STOPTest Step 3. Short the Sensor Signal at the Sensor Connector
Turn the keyswitch to the OFF/RESET position.
Connect Caterpillar Electronic Technician (ET) to the service tool connector.
Disconnect the suspect sensor from the harness.
Turn the keyswitch to the ON position.
Check the active diagnostic codes on Cat ET.
Use a suitable piece of wire to short terminal B (Analog Return) and terminal C (Signal) at the harness side of the suspect sensor connector.
Check the active diagnostic codes on Cat ET.Expected Result:The FMI for the active diagnostic code changes from a "03" (Open/Short to +Battery) to a "04" (Short to Ground) when the terminals are shorted.Results:
OK - The harness appears to be OK. The problem is with the sensor.Repair: Replace the suspect sensor.Verify that the repair eliminates the problem.STOP
Not OK - Proceed to Test Step 4.Test Step 4. Measure the Resistance of the Signal Wire
Illustration 2 g00711975
ECM connector P1
Illustration 3 g00711977
ECM connector P2
Disconnect the suspect sensor and the appropriate ECM connector for that sensor.
Measure the resistance between terminal C (Signal) at the harness side of the suspect sensor connector and the appropriate terminal for the sensor signal at the ECM connector.Expected Result:The resistance through the signal wire is less than 10 Ohms.Results:
OK - Proceed to Test Step 5.
Not OK - There is an open circuit or excessive resistance in the signal circuit of the harness.Repair: Repair the circuit.Verify that the repair eliminates the problem.STOPTest Step 5. Short the Sensor Signal at the ECM
Illustration 4 g00712006
J1/P1 breakout
Illustration 5 g00711977
J2/P2 breakout
Turn the keyswitch to the OFF/RESET position and install 7X-1715 Adapter Cables at ECM connectors J1/P1 and J2/P2.
Remove the suspect signal wire from the appropriate ECM connector.
Turn the keyswitch to the ON position.
Check the active diagnostic codes on Cat ET.
Use a suitable piece of wire to short the terminal for the suspect sensor signal to P1:5 (−Battery) at the breakout.
Check the active diagnostic codes on Cat ET.Expected Result:The FMI for the active diagnostic code changes from a "03" (Open/Short to +Battery) to a "04" (Short to Ground) when the terminals are shorted.Results:
OK - There is a problem in the wiring between the suspect sensor and the ECM.Repair: Repair the circuit.Verify that the repair eliminates the problem.STOP
Not OK - The ECM is not reading the sensor circuit.Repair: Verify your results. Replace the ECM. Refer to Troubleshooting, "Replacing the ECM" before you replace the ECM.Verify that the repair eliminates the problem.STOP