PLATE 1496974 - Caterpillar

Illustration 1 g00770279
SchematicTest Step 1. Inspect Electrical Connectors and Wiring
Turn the keyswitch to the OFF/RESET position.
Thoroughly inspect the J1/P1 ECM connector, J3/P3 machine connector, 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 for Shorts in the Harness from the ECM to the Digital Sensor
Illustration 2 g00938902
P1 ECM connector
Disconnect the J1/P1 ECM connector and the digital sensor.
Measure the resistance between P1:35 (Digital Sensor +8 VDC) and engine ground.
Measure the resistance between P1:35 (Digital Sensor +8 VDC) and P1:29 (Digital Sensor Return).Expected Result:The resistance is greater than 20,000 Ohms for each measurement.Results:
OK - Proceed to Test Step 3.
Not OK - There is a short between the ECM and the sensor.Repair: Repair the circuit.STOPTest Step 3. Check for Open Circuits in the Harness Between the ECM and the Digital Sensor
Illustration 3 g00938902
J1/P1 breakout
Turn the keyswitch to the OFF/RESET position and install a 7X-1715 Adapter Cable (40 Pin Breakout T) at ECM connector J1/P1.
Use a suitable piece of wire to short P1:35 (Digital Sensor +8 VDC) and P1:29 (Digital Return) at the breakout.
Disconnect the digital sensor.
Measure the resistance between terminal A (+8 VDC) and terminal B (Ground) of the connector for the digital sensor.
Remove the wire short from the breakout.Expected Result:The resistance is less than 10 Ohms for each measurement.Results:
OK - Proceed to Test Step 4.
Not OK - There is an open circuit in the wiring harness between the sensor and the ECM.Repair: Repair the circuit.Verify that the repair eliminates the problem.STOPTest Step 4. Check the Digital Sensor Supply Voltage at the Sensor Connector
Disconnect the digital sensor.
Turn the keyswitch to the ON position.
Measure the voltage across terminal A (+8 VDC) and terminal B (Ground) of the connector for the digital sensor.Expected Result:The digital sensor supply voltage is 8.0 0.5 VDC.Results:
OK - The supply voltage is reaching the sensor. Proceed to Test Step 5.
Not OK - The supply voltage is not reaching the sensor. Proceed to Test Step 7.Test Step 5. Check the Digital Sensor for an Internal Short
Illustration 4 g00938902
J1/P1 breakout
Disconnect the digital sensor.
Turn the keyswitch to the ON position.
Reconnect the digital sensor while you observe the voltage across P1:35 (Digital Sensor +8 VDC) and P1:29 (Digital Sensor Return) at the breakout.Expected Result:The supply voltage is 8.0 0.5 VDC. The voltage should not drop when the sensor is connected.Results:
OK - The sensor does not have an internal short.Repair: Refer to Troubleshooting, "Electrical Connectors - Inspect" if the problem is intermittent.STOP
Not OK - The sensor may have an internal short. Proceed to Test Step 6.Test Step 6. Temporarily Install a New Sensor
Illustration 5 g00938902
J1/P1 breakout
Disconnect the suspect sensor and remove the suspect sensor.
Temporarily install a new sensor.
Turn the keyswitch to the ON