3406E, C12, C15 and C18 Marine Engines Caterpillar


Engine Pressure Sensor Open or Short Circuit - Test

Usage:

C-12 9HP
System Operation Description:

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

  • Engine oil pressure sensor

  • Fuel pressure sensor

  • Marine transmission oil pressure sensor

  • Turbocharger outlet pressure sensor

This procedure covers the following 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 short to +batt

  • 102-04 Boost Pressure Sensor short to ground

  • 127-03 Transmission Oil Pressure open/short to +batt

  • 127-04 Transmission Oil Pressure short to ground

The 5 volt sensor supply provides power to all 5 volt sensors. The Electronic Control Module (ECM) supplies 5.0 ± 0.2 VDC to terminal A of each sensor connector. The sensor return 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 1g00945199

Schematic for the engine pressure sensors

Test Step 1. Inspect the Electrical Connectors and the Wiring

  1. Turn the keyswitch to the OFF position.



    Illustration 2g01150167

    C12 engine pressure sensors (typical example)

    (1) Connector for the marine transmission oil pressure sensor

    (2) Turbocharger outlet pressure sensor

    (3) Fuel pressure sensor

    (4) Engine oil pressure sensor

    (5) J2/P2 ECM connectors




    Illustration 3g01150173

    3406E, C15, and C18 engine pressure sensors (typical example)

    (1) Connector for the marine transmission oil pressure sensor

    (2) Turbocharger outlet pressure sensor

    (3) Fuel pressure sensor

    (4) Engine oil pressure sensor

    (5) J2/P2 ECM connectors

  1. Thoroughly inspect connector (5). Thoroughly inspect the connectors for sensors (1), (2), (3), and (4). Refer to Troubleshooting, "Electrical Connectors - Inspect".



    Illustration 4g01150176

    P2 terminals that are associated with the engine pressure sensors

    (P2-2) +5 VDC

    (P2-3) Return

    (P2-14) Marine transmission oil pressure

    (P2-16) Fuel pressure

    (P2-24) Engine oil pressure

    (P2-40) Turbocharger outlet pressure

    (P2-41) +5 VDC

    (P2-42) Return




    Illustration 5g01123211

    Connectors for the sensors

    (A) Supply

    (B) Return

    (C) Signal

  1. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the engine pressure sensors.

  1. Check the allen head screw on each ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.

  1. Check the harness and wiring for abrasions and for pinch points from each sensor 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 the Voltage on the +5 V Supply Wire

  1. Turn the keyswitch to the OFF position.

  1. Disconnect the harness connectors for the following sensors:

    • Engine oil pressure sensor J201/P201

    • Turbocharger outlet pressure sensor J200/P200

    • Fuel pressure sensor J209/P209

    • Marine transmission oil pressure sensor J212/P212

  1. Turn the keyswitch to the ON position.

  1. Measure the voltage between terminals A (supply) and B (return) at each sensor connector on the engine harness.

  1. Turn the keyswitch to the OFF position.

  1. Connect all of the sensors.

Expected Result:

Each voltage measurement is 5.0 ± 0.2 VDC.

Results:

  • OK - Each voltage measurement is 5.0 ± 0.2 VDC. Proceed to Test Step 3.

  • Not OK - At least one voltage measurement is not 5.0 ± 0.2 VDC.

    Repair: Refer to Troubleshooting, "Analog Sensor Supply Circuit - Test".

    STOP

Test Step 3. Check for Active Diagnostic Codes

  1. Connect the Caterpillar Electronic Technician (ET) to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools".

  1. Turn the keyswitch to the ON position.

  1. Use Cat ET to check for active diagnostic codes. Wait at least 15 seconds so that any codes may become active. Look for an active diagnostic code for an engine pressure sensor.

  1. Determine if the problem is related to a 03 diagnostic code or to a 04 diagnostic code.

Expected Result:

No diagnostic codes are active.

Results:

  • OK - No diagnostic codes are active for the engine pressure sensors.

    Repair: If any of the above codes are logged and the engine is not running properly, refer to Troubleshooting, "Troubleshooting Without a Diagnostic Code".If the engine is running properly at this time, there may be an intermittent problem in a harness that is causing the codes to be logged. Refer to Troubleshooting, "Electrical Connectors - Inspect".

    STOP

  • Active 04 code - An 04 diagnostic code is active. Proceed to Test Step 4.

  • Active 03 code - An 03 diagnostic code is active. Proceed to Test Step 5.

Test Step 4. Disconnect the Suspect Sensor in Order to Create an Open Circuit

  1. Turn the keyswitch to the OFF position.

  1. Disconnect the harness connector of the sensor with the 04 diagnostic code.

  1. Turn the keyswitch to the ON position. Wait at least 15 seconds for activation of the diagnostic codes.

  1. Use Cat ET to check for active diagnostic codes. Check for an active 03 diagnostic code for the disconnected sensor.

  1. Turn the keyswitch to the OFF position.

Expected Result:

A 03 diagnostic code is now active for the disconnected sensor.

Results:

  • OK - A 04 diagnostic code was active before you disconnected the sensor. A 03 diagnostic code became active after the sensor was disconnected.

    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 04 diagnostic code was active before you disconnected the sensor. The 04 diagnostic code remained after the sensor was disconnected. There is a problem in the wiring harness or there is a problem with the ECM. Leave the sensor disconnected. Proceed to Test Step 8.

Test Step 5. Check the Pull-up Voltage at the Sensor Connector

  1. Turn the keyswitch to the ON position.

  1. Disconnect the suspect sensor.

  1. Measure the voltage between terminals C (signal) and B (return) at the harness connector for the suspect sensor.

  1. Turn the keyswitch to the OFF position.

Expected Result:

The voltage is 11 ± 2 VDC.

Results:

  • OK - The voltage is 11 ± 2 VDC. The signal wire to the ECM from the sensor connector is OK.

    Repair: The open circuit is in the sensor or the wire between the sensor and the sensor connector. Temporarily connect a new sensor to the engine harness. Do not install the sensor in the engine. Verify that no diagnostic codes are active for the new sensor before you permanently install the sensor.

    STOP

  • Not OK - The voltage is not 11 ± 2 VDC. Proceed to Test Step 6.

Test Step 6. Check the Signal Wire for a Short Circuit

  1. Turn the keyswitch to the OFF position.

  1. Disconnect the J1/P1 and J2/P2 ECM connectors.

  1. Ensure that the harness connector for the suspect sensor is disconnected.

  1. Identify the terminal for the signal wire on the ECM connector that is appropriate for the suspect sensor. Measure the resistance between the appropriate terminal and the remaining terminals on both ECM connectors.

  1. Measure the resistance between the appropriate terminal and the engine ground.

  1. Connect the J1/P1 and J2/P2 ECM connectors. Connect the connectors for the suspect sensor.

Expected Result:

Each resistance measurement indicates an open circuit.

Results:

  • OK - Each resistance measurement indicates an open circuit. Proceed to Test Step 7.

  • Not OK - At least one resistance measurement does not indicate an open circuit. There is a problem in the wiring for the sensor. There may be a problem with a connector.

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

    STOP

Test Step 7. Create a Short at the Suspect Sensor Connector

  1. Turn the keyswitch to the OFF position.

  1. Fabricate a jumper wire that will be long enough to jumper terminals B (return) and C (signal) on the harness connector for the suspect sensor.

  1. Turn the keyswitch to the ON position.

    Note: Monitor Cat ET for diagnostic codes before installing the jumper wire and after installing the jumper wire.

  1. Use Cat ET to check for active diagnostic codes. Wait at least 15 seconds so that any codes may become active. Look for a 04 diagnostic code.

  1. Remove the jumper wire.

  1. Turn the keyswitch to the OFF position.

Expected Result:

A 04 diagnostic code was active when the jumper wire was installed. A 03 diagnostic code became active when the jumper wire was removed.

Results:

  • OK - A 04 diagnostic code was active when the jumper wire was installed. A 03 diagnostic code became active when the jumper wire was removed.

    Repair: The engine harness and the ECM are OK. 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 new sensor, permanently install the new sensor. Clear any logged diagnostic codes.Verify that the problem is resolved.

    STOP

  • Not OK - A 04 diagnostic code was active when the jumper wire was installed. The 04 code remained when the jumper wire was removed. The problem is in the wiring harness or the ECM. 8

Test Step 8. Check the Operation of the ECM

  1. Turn the keyswitch to the OFF position.

  1. Check the operation of the ECM by creating an open circuit at the ECM connector:

    1. Disconnect the appropriate ECM connector.

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

    1. Connect the ECM connector.

    1. Turn the keyswitch to the ON position.

    1. Monitor the "Active Diagnostic Code" screen on Cat ET. Wait at least 15 seconds so that any codes may become active.

      A 03 diagnostic code should be active for the suspect sensor.

    1. Turn the keyswitch to the OFF position.

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

    1. Disconnect the appropriate ECM connector.

    1. Crimp a terminal onto a jumper wire that is long enough to connect from the ECM connector to engine ground. Install the terminal of the jumper wire into the appropriate terminal location of the ECM connector for the suspect sensor. Ground the other end of the jumper wire.

    1. Connect the ECM connector.

  1. Turn the keyswitch to the ON position.

  1. Monitor the "Active Diagnostic Code" screen on Cat ET. Wait at least 15 seconds so that any codes may become active.

    A short circuit diagnostic code (04) should be active when the wire jumper is installed.

  1. Turn the keyswitch to the OFF position.

  1. Remove the jumper wire. Return the wiring to the original configuration.

Expected Result:

A 03 diagnostic code is active when the sensor signal wire is removed from the ECM connector. A 04 diagnostic code is active when the signal wire is connected to ground.

Results:

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

    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 03 diagnostic code is not active when the sensor signal wire is disconnected. The 04 diagnostic code is not active when the wire jumper is installed.

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

    STOP

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