3512B Oil Well Servicing Engine (ADEM III) Caterpillar

Use this procedure to troubleshoot the electrical system if a problem is suspected with the exhaust temperature sensors or if any one of the diagnostic codes in Table 1 is active or easily repeated.

System Operation

Use this procedure to troubleshoot any suspect problems with the following sensors:

• Left exhaust temperature sensor

• Right exhaust temperature sensor

A digital supply voltage is routed to terminal A of each sensor connector. The sensor return is routed to terminal B of each sensor connector. The sensor signal is routed to terminal C of each sensor connector. 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	g01213936
Schematic for the pulse width modulated sensors

Illustration 2	g01228528
P1 ECM connector (P1-4) 8 V supply (P1-5) Digital return (P1-11) Left exhaust temperature (P1-12) Right exhaust temperature

Illustration 3	g01159881
Sensor connector (Terminal A) Sensor supply (Terminal B) Sensor return (Terminal C) Signal

Illustration 4	g01228531
Location of the exhaust temperature sensors (typical right side and left side engine views) (1) Right exhaust temperature sensor (2) Left exhaust temperature sensor

Test Step 1. Check for Active Diagnostic Codes

1. Connect Caterpillar Electronic Technician (ET) to the service tool connector.

2. 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.

3. 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 connector terminal.

4. Determine if one of the following diagnostic codes is active for one of the exhaust temperature sensors:

   • -3

   • -4

Expected Result:

No diagnostic codes are active for the exhaust temperature sensors.

Results:

• OK - No diagnostic codes are active. There are no active diagnostic codes, but a problem with the sensor is still suspected. Proceed to Test Step 5.

• Not OK - A -3 diagnostic code is active or the diagnostic code is logged several times. There is an open circuit or a short to the +Battery in one of the sensor circuits. Proceed to Test Step 2.

• Not OK - A -4 diagnostic code is active or the diagnostic code is logged several times. A short to ground has been detected in one of the sensor circuits. Proceed to Test Step 3.

Test Step 2. Create a Short at the Sensor Connector

1. Remove electrical power from the ECM.

2. Disconnect the suspect sensor.

3. Fabricate a jumper wire that is long enough to create a short circuit across two terminals at the sensor connector. Crimp connector pins to each end of the jumper wire.

4. Install the jumper wire between terminal C (signal) and terminal B (digital return) at the sensor connector.

5. Restore electrical power to the ECM.

6. Monitor the diagnostic codes on Cat ET. Check for an active -4 diagnostic code for the suspect sensor.

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

7. Remove electrical power from the ECM.

Expected Result:

A -4 diagnostic code is now active for the suspect sensor.

Results:

• OK - A -3 diagnostic code was active before creating the short at the sensor connector. A -4 diagnostic code became active after creating the short at the sensor connector.

  Repair: The harness and the ECM are OK. There is a problem with the sensor. Replace the sensor. Verify that there are no active diagnostic codes for the sensor. Clear any logged diagnostic codes.

  STOP

• Not OK - A -3 diagnostic code is still active for the suspect sensor. The problem is in the harness between the sensor connector and the ECM. There may be a problem with the ECM. Proceed to Test Step 4.

Test Step 3. Create an Open at the Suspect Sensor Connector

1. Remove electrical power from the ECM.

2. Disconnect the sensor connector of the suspect sensor with the active -4 diagnostic code.

3. Restore electrical power to the ECM.

4. Monitor the diagnostic codes on Cat ET. Check for an active -3 diagnostic code for the suspect sensor.

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

5. Remove electrical power from the ECM.

Expected Result:

A -3 diagnostic code is now active for the suspect sensor.

Results:

• OK - A -4 diagnostic code was active before disconnecting the sensor. A -3 diagnostic code became active after disconnecting the sensor.

  Repair: The harness and the ECM are OK. There is a problem with the sensor. Replace the sensor. Verify that there are no active diagnostic codes for the sensor. Clear any logged diagnostic codes.

  STOP

• Not OK - A -4 diagnostic code is still active for the suspect sensor. The problem is in the harness between the sensor connector and the ECM. There may be a problem with the ECM. Leave the sensor disconnected. Proceed to Test Step 4.

Test Step 4. Check for Proper Operation of the ECM

1. Remove electrical power from the ECM.

2. Check for proper operation of the ECM by creating an open at the ECM connector:

   1. Disconnect the J1/P1 ECM connectors.

   2. Fabricate a jumper wire that is long enough to create a test circuit between the ECM connector and the engine ground stud. Crimp a connector socket to one end of the jumper wire.

   3. Remove the signal wire for the suspect sensor from the P1 ECM connector. Refer to Illustration 1 for the correct terminal locations. Install the jumper wire into this terminal location for the signal wire of the suspect sensor.

   4. Connect the J1/P1 ECM connectors.

   5. Restore electrical power to the ECM.

      Hold the test wire away from any ground source in order to create an open circuit condition.

   6. Monitor the "Active Diagnostic Code" screen on Cat ET. Wait at least 30 seconds for activation of the code.

      An open circuit diagnostic code -3 will be active for the suspect sensor.

3. Check for proper operation of the ECM by creating a short at the ECM connector:

   1. Connect the loose end of the signal wire for the suspect sensor to the engine ground stud.

   2. Monitor the "Active Diagnostic Code" screen on Cat ET. Wait at least 30 seconds for activation of the code.

      A -4 diagnostic code will be active when the jumper wire is shorted to engine ground.

   3. Remove the jumper wire. Reconnect all wires and connectors.

Expected Result:

A -3 diagnostic code is active when the sensor signal wire is removed from the ECM connector. A -4 diagnostic code is active when the signal wire is connected to engine ground.

Results:

• OK - The ECM is operating properly. The problem is in the wiring between the ECM and the connector for the sensor.

  Repair: If the code is active for more than one sensor, the problem is most likely in the return wire for the sensor. Repair the return wire for the sensor or replace the harness.

  If the code is only active for one sensor, the problem is most likely in the signal wire for the sensor. Repair the signal wire for the sensor.

  STOP

• Not OK - One of the following conditions exists: The -3 diagnostic code is not active when the sensor signal wire is disconnected. The -4 diagnostic code is not active when the wire jumper is shorted to ground.

  Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM". Verify that the problem is resolved.

  STOP

Test Step 5. Check the Digital Supply Voltage at the Sensor Connector

1. Disconnect the suspect sensor at the sensor connector:

2. Measure the voltage on the harness side of the sensor connector between pin A and pin B of the suspect sensor.

Expected Result:

The supply voltage is 8.0 ± 0.4 VDC.

Results:

• OK - The supply voltage is 8.0 ± 0.4 VDC. Proceed to Test Step 7.

• Not OK - The supply voltage is not 8.0 ± 0.4 VDC. Proceed to Test Step 6.

Test Step 6. Check the Digital Supply Voltage at the ECM

1. Remove electrical power from the ECM.

2. Disconnect the J1/P1 ECM connectors.

3. Fabricate a jumper wire that is long enough to create a test circuit between the ECM connector and the engine ground stud. Crimp a connector socket to one end of the jumper wire.

4. Remove the supply wire from terminal location P1-4 (+8 V supply). Install the jumper wire into this terminal location.

5. Connect the J1/P1 ECM connectors.

6. Restore electrical power to the ECM.

7. Measure the voltage between the jumper that is in terminal location P1-4 and the engine ground stud.

8. Remove electrical power from the ECM.

Expected Result:

The supply voltage is 8.0 ± 0.4 VDC.

Results:

• OK - The supply voltage is 8.0 ± 0.4 VDC. The supply voltage at the ECM is correct. There is a problem in the wiring harness between the ECM and the sensor connector.

  Repair: Repair the wiring harness and/or the connectors. Replace parts, if necessary. Verify that the original problem is resolved.

  STOP

• Not OK - The supply voltage is not 8.0 ± 0.4 VDC. The voltage at the ECM is not correct.

  Repair: Replace the ECM. Refer to Troubleshooting, "Replacing the ECM". Verify that the problem is resolved.

  STOP

Test Step 7. Check the Sensor's Duty Cycle at the Sensor Connector

1. Remove electrical power from the ECM.

2. On the sensor side of the sensor connector, remove the suspect sensor's signal wire (pin C) from the sensor connector.

3. Reconnect the suspect sensor connector.

4. Restore electrical power to the ECM.

5. Measure the duty cycle between the sensor's signal wire and pin B of the sensor connector.

   Note: Set the multimeter to "VDC". Press the "Hz" button twice so that the % symbol is displayed.

6. Remove electrical power from the ECM.

7. Replace the sensor's signal wire and reconnect the sensor.

Expected Result:

The duty cycle is between 10 to 90 percent.

Results:

• OK - The duty cycle is correct. Proceed to Test Step 8.

• Not OK - The duty cycle is incorrect.

  Repair: Replace the sensor. Verify that no diagnostic codes are active for the suspect sensor before permanently installing the sensor.

  STOP

Test Step 8. Check the Sensor's Duty Cycle at the ECM

1. Remove electrical power from the ECM.

2. Remove the suspect signal wire for the sensor from ECM connector P1. Refer to Illustration 1 for the correct terminal locations at the ECM connector.

3. Restore electrical power to the ECM.

4. Measure the duty cycle between the sensor's signal wire and the sensor's return wire.

   Note: Set the multimeter to "VDC". Press the "Hz" button twice so that the % symbol is displayed.

5. Remove electrical power from the ECM.

   Restore the wiring to the original configuration.

Expected Result:

The duty cycle is between 10 to 90 percent.

Results:

• OK - The duty cycle is correct.

  Repair: Replace the ECM. Refer to the diagnostic procedure Troubleshooting, "Replacing the ECM".

  STOP

• Not OK - The duty cycle is not correct.

  Repair: There is a problem in the wiring between the ECM and the connector for the sensor. Repair the connectors and/or wiring between the ECM and the connector for the sensor.

  STOP