Use this procedure to troubleshoot any suspect problems with the auxiliary temperature sensor.
Use this procedure to troubleshoot the 1836-08 Auxiliary Temperatue Sensor signal abnormal.
The auxiliary temperature sensor receives a regulated voltage supply of 8.0 ± 0.4 VDC from the Electronic Control Module (ECM).
Note: Refer to the diagnostic functional test Troubleshooting, "Digital Sensor Supply Circuit - Test" if the ECM has detected a problem with the digital sensor supply voltage.
The ECM performs an automatic calibration of this sensor whenever the ECM is powered and the engine has been off for at least five seconds.
Verify that the auxiliary temperature sensor has been installed. Verify that the auxiliary temperature sensor has been programmed to "Installed" on the configuration screen of the Caterpillar Electronic Technician (ET). If the auxiliary temperature is not programmed, Cat ET will display "Not Installed" on the status screen.
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| Illustration 1 | g01080717 |
Schematic for auxiliary temperature sensor | |
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The connection of any electrical equipment and the disconnection of any electrical equipment may cause an explosion hazard which may result in injury or death. Do not connect any electrical equipment or disconnect any electrical equipment in an explosive atmosphere. |
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Note: The circuit for the auxiliary temperature sensor utilizes a resistor assembly that is wired in parallel across the signal wire and the return wire. The resistor is used to condition the pulse width modulated signal for the ECM. If the resistor is not present in the circuit then diagnostic codes for the sensor will become active. The resistor is installed in the harness between the customer connector and the sensor connector.
Test Step 1. Verify that the Auxiliary Temperature Sensor is Installed
- Locate the auxiliary temperature sensor on the installation. Verify that a auxiliary temperature sensor is installed.
Expected Result:
The auxiliary temperature sensor is installed.
Results:
- OK - The auxiliary temperature sensor is installed. Proceed to Test Step 2.
- Not OK - The auxiliary temperature sensor is not installed.
Repair: Change the parameter for the auxiliary temperature sensor to "Not Installed". Verify that the repair eliminates the problem.
STOP
Test Step 2. Inspect the Electrical Connectors and the Wiring
- Turn the keyswitch to the OFF position.
- Thoroughly inspect connectors (1) and (2). Also inspect the connector for the auxiliary temperature sensor. Refer to Troubleshooting, "Electrical Connectors - Inspect".
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| Illustration 2 | g01146374 |
Left side engine view (typical example) (1) J1/P1 ECM connectors | |
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| Illustration 3 | g01146383 |
Left side engine view (typical example) (2) P61 customer connector | |
- Perform a 45 N (10 lb) pull test on each of the wires that is associated with the auxiliary temperature sensor circuit.
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| Illustration 4 | g01102095 |
ECM P1 connector (P1-4) +8 V Supply (P1-5) Return (P1-68) Auxiliary temperature sensor signal | |
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| Illustration 5 | g01102110 |
J61 and P61 connectors (8) +8 V supply (9) Return (11) Auxiliary temperature sensor signal | |
- Check the torque of the allen head screws for the ECM connectors and the customer connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Expected Result:
All connectors, pins, and sockets are completely coupled and/or inserted, and the harness and wiring are free of corrosion, of abrasion, and of pinch points.
Results:
- OK - The connectors and wiring are OK. Proceed to Test Step 3.
- Not OK - There is a problem in the connectors and/or wiring.
Repair: Repair the wiring and connectors or replace the wiring or the connectors. Ensure that all of the connector seals are in place. Verify that the repair eliminates the problem.Verify that the repair eliminates the problem.
STOP
Test Step 3. Check the Sensor Supply Voltage at the Sensor Connector
- Disconnect the auxiliary temperature sensor.
- Turn the keyswitch to the ON position.
- Use a multimeter to measure the voltage between terminal A (+8 V digital supply) and terminal B (sensor return) at the harness connector for the auxiliary temperature sensor.
- Turn the keyswitch to the OFF position.
Expected Result:
The digital sensor supply voltage between terminal A (+8 V digital supply) and terminal B (sensor return) is 8.0 ± 0.4 VDC.
Results:
- OK - The supply voltage is reaching the sensor. Proceed to Test Step 4.
- Not OK - The digital sensor supply voltage is not reaching the sensor.
Repair: Refer to the diagnostic functional test Troubleshooting, "Digital Sensor Supply Circuit - Test" for the appropriate troubleshooting procedure.
STOP
Test Step 4. Check for Active Diagnostic Codes
- Connect the Cat ET to the service tool connector.
- Turn the keyswitch to the ON position.
- Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes.
Note: Wait at least 15 seconds in order for the diagnostic codes to become active.
Expected Result:
No diagnostic codes are active.
Results:
- OK - No diagnostic codes are active.
Repair: The problem may have been related to a faulty connection in the harness. Carefully reinspect the connectors and wiring. Refer to Troubleshooting, "Electrical Connectors - Inspect".
STOP
- Not OK - A 1836-08 diagnostic code is active. Proceed to Test Step 5.
Test Step 5. Check for a Short in the Signal Wire
- Disconnect the following connectors.
- P142/J142 (auxiliary temperature sensor)
- J1/P1 (ECM connectors)
- J2/P2 (ECM connectors)
- P142/J142 (auxiliary temperature sensor)
- Measure the resistance between the suspect sensor's signal wire and every terminal on the P1 and P2 connectors.
Wiggle the harness during each measurement in order to locate any opens or shorts in the harness.
- Measure the resistance between the sensor's signal wire and the engine ground stud.
Expected Result:
Each check of the resistance indicates an open circuit.
Results:
- OK - Each check of the resistance indicates an open circuit. The signal wire is not shorted to another wire that is in the harness. Leave the connectors disconnected. Proceed to Test Step 6.
- Not OK - At least one resistance measurement did not indicate an open circuit. There is a short from the signal wire to another wire in the harness.
Repair: Repair the connectors or wiring. If necessary, replace the connectors or the wiring. Verify that the repair eliminates the problem.
STOP
Test Step 6. Check for an Open in the Signal Wire
- Measure the resistance between P1-68 (auxiliary temperature sensor signal ) and terminal "P142-C" on the harness connector for the auxiliary temperature sensor.
Wiggle the harness during the measurement in order to locate any opens or shorts in the harness.
Expected Result:
The resistance is less than five Ohms.
Results:
- OK - The resistance is less than five Ohms. There is not an open in the signal wire. Proceed to Test Step 7.
- Not OK - The resistance is more than five Ohms. There is an open circuit or excessive resistance in the signal wire.
Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Verify that the repair eliminates the problem.
STOP
Test Step 7. Check the Resistance of the Harness
- Install a jumper wire between terminals P142-B (auxiliary temperature sensor return) and P142-C (auxiliary temperature sensor signal).
- Measure the resistance between terminals P1-68 (auxiliary temperature sensor signal) and P1-5 (auxiliary temperature sensor return) at the ECM connector.
The correct resistance for the circuit is 1700 Ohms to 1900 Ohms.
Expected Result:
The resistance measurement for the circuit is within specifications.
Results:
- OK - The resistance measurement is within specifications. Remove the jumper wire. Connect the J1/P1 and the J2/P2 ECM Connectors. Proceed to Test Step 8.
- Not OK - The resistance measurement is not within specifications.
Repair: Locate the resistor in the sensor harness. Replace the resistor. Ensure that the wire splice that is used for the installation of the wiring for the resistor is providing a good connection. Verify that the repair eliminates the problem.
STOP
Test Step 8. Check the Digital Sensor's Signal Frequency and the Duty Cycle at the Sensor Connector
- Turn the keyswitch to the OFF position.
- Install a breakout T between J142 and P142 at the sensor connector.
- Reconnect the suspect sensor.
- Turn the keyswitch to the ON position.
- Measure the frequency and the duty cycle between terminal C (sensor signal) and terminal B (sensor return) of the breakout T.
Wiggle the harness during the measurement in order to locate any opens or shorts in the harness.
- Turn the keyswitch to the OFF position.
- Remove the breakout T. Reconnect the sensor.
Expected Result:
The frequency reading is 500 ± 200 Hz. The duty cycle is between 10 percent to 89 percent.
Results:
- OK - The frequency and the duty cycle are correct. Proceed to Test Step 9.
- Not OK - The frequency and the duty cycle are not correct.
Repair: Replace the sensor. Verify that the problem is resolved.
STOP
Test Step 9. Check the Digital Sensor's Signal Frequency and the Duty Cycle at the ECM
- Turn the keyswitch to the OFF position.
- Install a breakout T at the ECM between connectors J1 and P1.
- Turn the keyswitch to the ON position.
- Measure the frequency and the duty cycle between terminal P1-5 (sensor return) and terminal P1-68 (Auxiliary temperature sensor signal) of the breakout T.
Wiggle the harness during the measurement in order to locate any opens or shorts in the harness.
- Turn the keyswitch to the OFF position.
- Remove the breakout T. Connect P1 to J1.
Expected Result:
The frequency reading is 500 ± 200 Hz. The duty cycle is between 10 percent to 89 percent.
Results:
- OK - The frequency and the duty cycle are correct.
Repair: Verify that the diagnostic code is still active. If the diagnostic code is still active and the wire for the signal is OK, replace the ECM. Refer to Troubleshooting, "Replacing the ECM".Verify that the repair eliminates the problem.
STOP
- Not OK - The frequency and the duty cycle are not correct. The problem is in the J1/P1 ECM connectors.
Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Verify that the repair eliminates the original problem.
STOP