TUBE AS 3279079 - Caterpillar

System OperationUse this procedure to troubleshoot any suspect problems with the following sensors:
Left exhaust temperature sensor
Right exhaust temperature sensorThe PWM sensors provide a signal to the engine's ECM for certain engine operating conditions. The sensors receive a 8.0 0.4 VDC regulated voltage from the ECM.The sensor's wires are routed from the ECM to the sensor connectors. The following list gives the terminal locations for the sensor connector.
Terminal A 8 V supply
Terminal B sensor return
Terminal C sensor signalThe ECM performs an automatic calibration of these sensors whenever the ECM is powered and the engine has been off for at least five seconds.The ECM provides short circuit protection for the internal power supply. A short circuit to the battery will not damage the internal power supply.
Illustration 1 g01208743
Sensor locations
(1) Left exhaust temperature sensor
(2) Right exhaust temperature sensor
Illustration 2 g01205563
Typical schematic
Illustration 3 g01205567
P1 ECM connector
(P1-4) 8 V supply
(P1-11) Left exhaust temperature
(P1-12) Right exhaust temperature
(P1-60) Digital return
Illustration 4 g01205569
P2 ECM connector
(P2-55) Digital return
Illustration 5 g01094844
Sensor connector
(Pin A) Sensor supply
(Pin B) Sensor return
(Pin C) Signal Test Step 1. Check for an "Active" or "Logged" Diagnostic Code
Connect Caterpillar Electronic Technician (ET) to the service tool connector.
Monitor the diagnostic codes on Cat ET. Check and record any diagnostic codes. Note: Wait at least 30 seconds in order for the diagnostic codes to become active.
Determine if a diagnostic code has occurred several times. Note: A diagnostic code that is logged several times is an indication of an intermittent problem. Most intermittent problems are the result of a bad connection between a socket and a pin in a connector or a bad connection between a wire and a terminal.
Determine if a 08 diagnostic code is active or if a 08 diagnostic code has been logged. Expected Result:No diagnostic code is active for the exhaust temperature sensors.Results:
OK - No diagnostic codes are active.Repair: If the problem is intermittent, refer to Troubleshooting, "Inspecting Electrical Connectors" for the correct procedures for inspecting electrical connectors.STOP
Not OK - A diagnostic code is active or the diagnostic code is logged several times. Proceed to Test Step 2.Test Step 2. Perform the "Wiggle Test" on Cat ET
Select the "Wiggle Test" from the diagnostic tests on Cat ET.
Choose the appropriate group of parameters to monitor.
Press the "Start" button. Wiggle the wiring harness for the suspect sensor in order to reproduce an intermittent problem. If an intermittent problem is detected, the status will be highlighted and an audible beep will be heard.Expected Result:No intermittent problems were detected during the "Wiggle Test".Results:
OK - No intermittent problems were found. The harness and connectors appear to be OK. Proceed to Test Step 3 and continue to troubleshoot the active diagnostic code.
Not OK - At least one intermittent problem was indicated.Repair: Repair the harness or the connector. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors". Verify that the repair eliminates the problem.STOPTest Step 3. Check the Digital Supply Voltage at the Sensor Connector
Disconnect the suspect sensor(s) at the sensor connector:
Measure the voltage on the ECM side of the sensor connector between pin