C11 and C13 Engines for Caterpillar Built Machines Engine Pressure Sensor Open or Short Circuit - Test Caterpillar

System Operation Description:

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

• Fuel pressure sensor

• Engine oil pressure sensor

• Boost pressure sensor

• Atmospheric pressure sensor

This procedure covers the following open circuit diagnostic codes and short circuit diagnostic codes:

• 94-03 Fuel Pressure open/short to +batt

• 94-04 Fuel Pressure short to ground

• 100-03 Engine Oil Pressure open/short to +batt

• 100-04 Engine Oil Pressure short to ground

• 102-03 Boost Pressure Sensor open/short to +batt

• 102-04 Boost Pressure Sensor short to ground

• 274-03 Atmospheric Pressure open/short to +batt

• 274-04 Atmospheric Pressure short to ground

The 5 volt sensor supply provides power to all 5 volt sensors. The Electronic Control Module (ECM) supplies 5.0 ± 0.5 VDC to terminal A of each sensor connector. The sensor common from the ECM connector goes to terminal B of each sensor connector. The sensor supply is output short circuit protected. A short circuit to the battery will not damage the circuit inside the ECM.

Note: The sensors are not protected from overvoltage. A short from the supply line to the +Battery may damage the sensors. If the CID-FMI 262-03 is logged, it is possible that all of the sensors have been damaged. Repair the sensor supply and check for any "ACTIVE" sensor diagnostic codes in order to determine if a sensor has failed.

Pull-up Voltage

The ECM continuously outputs a pull-up voltage on the circuit for the sensor signal wire. The ECM uses this pull-up voltage in order to detect a problem in the signal circuit. When the ECM detects the presence of a voltage that is above a threshold on the signal circuit, the ECM will generate a 03 diagnostic code for the sensor.

If the sensor is disconnected at the sensor connector, the presence of pull-up voltage at the sensor connector indicates that the wires from the sensor connector to the ECM are OK. If the sensor is disconnected at the sensor connector, the absence of pull-up voltage at the sensor connector indicates a problem in the signal wire. If the sensor is disconnected at the sensor connector and the voltage at the sensor connector is different from pull-up voltage, the signal wire is shorted to another wire in the harness.

Illustration 1	g01119633
Schematic

Illustration 2	g01024457
P2 ECM connector (P2-15) Boost pressure sensor (P2-17) Sensor common (P2-28) Engine oil pressure sensor (P2-40) Fuel pressure sensor (P2-57) Atmospheric pressure sensor (P2-72) +5 V Supply

Illustration 3	g01119636
C13 Sensor locations (1) Atmospheric pressure sensor (2) Fuel pressure sensor (3) Engine oil pressure sensor (4) Boost pressure sensor

Illustration 4	g01252438
C15 and C18 Sensor locations (5) Boost pressure sensor (6) Fuel pressure sensor (7) Atmospheric pressure sensor (8) Engine oil pressure sensor

Illustration 5	g01094844
Sensor connector

Test Step 1. Inspect Electrical Connectors and Wiring

1. Turn the keyswitch to the OFF position.

2. Thoroughly inspect the J1/P1 ECM connector and the J2/P2 ECM connector. Thoroughly inspect the connectors for each analog sensor.

   Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

3. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector and the sensor connectors that are associated with the active diagnostic code.

4. Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

5. Check the harness and wiring for abrasions and for pinch points from the sensors back to the ECM.

Expected Result:

All connectors, pins, and sockets are completely coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion, and of pinch points.

Results:

• OK - The harness and wiring are OK. Proceed to Test Step 2.

• Not OK - There is a problem in the connectors and/or wiring.

  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 completely coupled.

  Verify that the repair eliminates the problem.

  STOP

Test Step 2. Check for "Active" or "Logged" Diagnostic Codes

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

2. Restore electrical power to the ECM.

3. 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.

4. 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. The problem may be caused by moisture, corrosion, or wear.

5. Determine if the problem is active and related to one of the following diagnostic codes:

   • -3

   • -4

Expected Result:

A diagnostic code is not active.

Results:

• OK - A diagnostic code is not active.

  Repair: The problem may be intermittent. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - A diagnostic code is active. Proceed to Test Step 3.

Test Step 3. Check the 5 Volt Supply Voltage at the Sensor Connector

1. Do not disconnect the suspect connector.

2. Connect a voltmeter between pin A and pin B on the sensor side of the connector for the suspect sensor.

3. Measure the voltage between pin A and pin B for the suspect sensor(s).

4. Wiggle the harness while you monitor the voltage on the voltmeter. Perform the 45 N (10 lb) pull test on each wire in the circuit. Each terminal and each connector should easily withstand 45 N (10 lb) of tension and each wire should remain in the connector body. This test checks whether the wire was properly crimped in the terminal and whether the terminal was properly inserted into the connector.

Expected Result:

The supply voltage is 5.0 ± 0.5 VDC.

Results:

• OK - The voltage is 5.0 ± 0.5 VDC. An active -3 diagnostic code is present. Proceed to Test Step 4.

• OK - The voltage is 5.0 ± 0.5 VDC. An active -4 diagnostic code is present. Proceed to Test Step 6.

• Not OK - The voltage is not 5.0 ± 0.5 VDC. Proceed to Test Step 8.

Test Step 4. Check for a Short to the +Battery at the Sensor Connector

1. Measure the voltage on the harness side of the sensor connector between pin B and pin C for the suspect sensor(s).

Expected Result:

The voltage is less than battery voltage.

Results:

• OK - The voltage is less than battery voltage. Proceed to Test Step 5.

• Not OK - The voltage is equal to battery voltage.

  Repair: There is a short in the harness to the +Battery. Repair the wiring.

  STOP

Test Step 5. Create a Short at the Sensor Connector

1. Remove electrical power from the ECM.

2. Disconnect the suspect sensor.

3. Use a wire jumper in order to create a short between terminal C (signal) and terminal B (sensor return) at the sensor connector.

4. Restore electrical power to the ECM.

5. 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.

6. Remove electrical power from the ECM.

Expected Result:

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

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. The harness and the ECM are OK. There may be a problem with the sensor.

  Repair: Temporarily connect a new sensor to the harness, but do not install the new sensor in the engine. Verify that there are no active diagnostic codes for the sensor. If there are no active diagnostic codes for the sensor, permanently install the new sensor. Clear any logged diagnostic codes.

  STOP

• Not OK - A -3 diagnostic code is still active for the suspect sensor(s). The problem may be in the harness or with the ECM. Proceed to Test Step 7.

Test Step 6. Create an Open at the Suspect Sensor Connector

1. Remove electrical power from the ECM.

2. Disconnect the sensor connector of the suspect sensor(s) 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(s).

Results:

• OK - A -4 diagnostic code was active before disconnecting the sensor. A -3 diagnostic code became active after disconnecting the sensor. The harness and the ECM are OK. There may be a problem with the sensor.

  Repair: Temporarily connect a new sensor to the harness, but do not install the new sensor in the engine. Verify that there are no active diagnostic codes for the sensor. If there are no active diagnostic codes for the sensor, permanently install the new sensor. Clear any logged diagnostic codes.

  STOP

• Not OK - A -4 diagnostic code is still active for the suspect sensor. Leave the sensor disconnected. The problem may be in the harness or with the ECM. Proceed to Test Step 7.

Test Step 7. Test the Operation of the ECM

1. Fabricate jumper wires that can be used to replace the signal wire in the ECM connector for the suspect sensor. Crimp a connector socket to one end of the jumper wire.

2. Disconnect the appropriate ECM connector for the suspect sensor.

3. Remove the signal wire for the suspect sensor from the ECM connector.

4. Install the jumper wire into the terminal location for the suspect sensor at the ECM connector.

5. Connect the ECM connector.

6. Check the operation of the ECM by creating an open at the ECM:

   1. Hold the loose end of the jumper wire away from any components in order to create an open circuit condition.

   2. Remove electrical power from the ECM.

   3. Monitor the active diagnostic code screen on Cat ET. Check for a -3 diagnostic code for the suspect sensor.

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

7. Check the operation of the ECM by creating a short circuit at the ECM:

   1. Short the jumper wire for the suspect sensor to engine ground in order to create a short circuit condition.

   2. Turn the ECS to the STOP position.

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

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

8. Remove all jumper wires. Return the wiring to the original configuration.

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 8. Check the Supply Voltage at the ECM

1. Remove electrical power from the ECM.

2. Remove the supply wire from the appropriate ECM connector. Install a wire jumper(s) into the socket(s) for the sensor supply.

3. Restore electrical power to the ECM.

4. Measure the voltage between the wire jumper(s) and engine ground.

5. Remove electrical power from the ECM.

6. Remove the wire jumpers and replace all wires.

Expected Result:

The supply voltage is 5.0 ± 0.5 VDC.

Results:

• OK - The supply voltage is 5.0 ± 0.5 VDC. The supply voltage at the ECM is correct. There is a problem in the wiring between the ECM and the sensor connector. Check the supply wire and the return wire for an open circuit.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring.

  STOP

• Not OK - The supply voltage is not 5.0 ± 0.5 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