DISTRIBUTION 3929005 - Caterpillar

Table 2
Troubleshooting Test Steps     Values     Results    
1. Inspect the Electrical Connectors and the Wiring
A. Turn the main disconnect switch to the OFF position.
B. Thoroughly inspect the ECM connectors. Inspect all of the connectors that are associated with the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
C. Perform a
45 N (10 lb) pull test on each of the wires in the ECM connectors that are associated with the circuit.
D. Check the allen head screw for each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
E. Check the harness and wiring for abrasion and for pinch points from the actuator back to the ECM.
   
Connectors
   
Results: The harness and connectors appear to be OK.
Proceed to Test Step 2.
Results: The harness and connectors are Not OK.
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 coupled.
Verify that the repair eliminates the problem.
   
2. Check the Operation of the Heating Element for the Suspect Sensor
A. Ensure that the electrical power has been removed from the engine.
B. Turn the engine control to the STOP position.
C. Remove the suspect sensor from the exhaust system.
D. Allow several minutes for the heating element to heat. Use an infrared thermometer to check the temperature at the tip of the oxygen sensor. The heating element tip will heat the tip of the sensor to
600 to 800° C (1100 to 1500° F).
E. Remove electrical power from the engine.
   
600 to 800° C (1100 to 1500° F)    
Results: The heating element is heating the tip of the sensor to
600 to 800° C (1100 to 1500° F).
Proceed to Test Step 7.
Results: The tip of the sensor is not heating to the correct temperature. There is a problem with the heating element. The sensor may not be receiving the correct supply voltage.
Proceed to Test Step 3.    
3. Measure the Voltage from the Buffer at the Sensor Connector
A. Disconnect the sensor connector that is between the tip of the sensor and the sensor buffer.
B. Set the engine control to the STOP position.
C. Use a multimeter to measure the voltage between terminal 1 (12 VDC) and terminal 2 (return) on the connector for the buffer. The connector is between the sensor and the sensor buffer.
D. Remove electrical power from the engine.
   
12 VDC    
Results: 12 V is available at the sensor connector. Supply voltage is available at the oxygen sensor.
Repair: The heating element is not heating the sensor, but the sensor is receiving the correct voltage. There is a problem with the sensor. Replace the sensor.
Verify that the repair eliminates the problem/
Results: 12 V is not available at the terminals of the sensor connector between the sensor and the sensor buffer. The supply voltage is not available at the sensor. There may be a problem with the sensor buffer or there may be a problem with the voltage