3126B Petroleum Engine 5 Volt Engine Pressure Sensor Supply Circuit - Test Caterpillar


5 Volt Engine Pressure Sensor Supply Circuit - Test
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System Operation Description:

The Electronic Control Module (ECM) creates a regulated voltage of 5.0 ± 0.2 VDC that is supplied to terminal A of the harness connectors for these sensors:

  • Injection actuation pressure sensor

  • Boost pressure sensor

  • Atmospheric pressure sensor

  • Fuel pressure sensor

  • Engine oil pressure sensor

  • Auxiliary pressure sensor

This procedure covers the following diagnostic codes:

  • 262-03 5 Volt Sensor DC Power Supply short to +batt

  • 262-04 5 Volt Sensor DC Power Supply short to ground

A +5 V diagnostic code is probably caused by a short circuit to ground or a short circuit to another voltage source in the harness. The next likely cause is a problem with a sensor. The least likely cause is a problem with the ECM.




Illustration 1g01128578

Schematic for the 5 volt supply

Test Step 1. Inspect the Electrical Connectors and the Wiring

  1. Turn the keyswitch to the OFF position.



    Illustration 2g01128582

    Left side view

    (1) Injection actuation pressure sensor

    (2) Boost pressure sensor

    (3) Atmospheric pressure sensor

    (4) Fuel pressure sensor

    (5) Engine oil pressure sensor

    (6) J2/P2 ECM connector

    (7) J1/P1 ECM connector

  1. Thoroughly inspect connectors (6) and (7). Thoroughly inspect the connectors for each pressure sensor. Refer to Troubleshooting, "Electrical Connectors - Inspect".



    Illustration 3g01128590

    P2 terminals that are associated with the 5 volt supply for the pressure sensors

    (P2-2) +5 VDC

    (P2-3) Return




    Illustration 4g01128693

    P1 terminals that are associated with the 5 volt supply for the pressure sensors

    (P1-2) +5 VDC

    (P1-3) Return




    Illustration 5g01128703

    J61/P61 terminals that are associated with the 5 volt supply for the pressure sensors

    (14) +5 VDC

    (15) Return




    Illustration 6g01123211

    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 pressure sensor supply.

  1. Check the torque of the allen head screw on the ECM connectors and the customer connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.

  1. Check the harness and the wiring for abrasion and for pinch points from each sensor back to the ECM.

Expected Result:

All of the 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 harness and connectors appear to be OK. Proceed to Test Step 2.

  • Not OK - The connectors and/or wiring are not OK.

    Repair: Repair the wiring and/or the connectors. Replace parts, if necessary. 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 Diagnostic Codes

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

  1. Turn the keyswitch to the ON position.

  1. Observe the "Active Diagnostic" screen on Cat ET. Wait at least 15 seconds so that any codes may become active. Look for these codes:

    • 262-03

    • 262-04

Expected Result:

One of the above codes is active.

Results:

  • Active 262-03 code - An 262-03 diagnostic code is active. Proceed to Test Step 3.

  • Active 262-04 code - An 262-04 diagnostic code is active. Proceed to Test Step 4.

  • No active codes - None of the above codes are active.

    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

Test Step 3. 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:

    • Injection actuation pressure sensor

    • Boost pressure sensor

    • Atmospheric pressure sensor

    • Fuel pressure sensor

    • Engine oil pressure sensor

    • Auxiliary pressure sensor

  1. Turn the keyswitch to the ON position.

    Note: Be sure to wiggle the harness during the following measurements in order to reveal an intermittent condition.

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

Expected Result:

Each voltage measurement is 5.0 ± 0.2 VDC.

Results:

  • OK - Each voltage measurement is 5.0 ± 0.2 VDC. The sensors are receiving the correct voltage.

    Repair: Connect all of the sensor connectors. Clear all diagnostic codes. Check for active diagnostic codes. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".

    STOP

  • Not OK - At least one voltage measurement is not 5.0 ± 0.2 VDC. There is a problem with the wiring or with the ECM. Proceed to Test Step 5.

Test Step 4. Disconnect the +5 V Pressure Sensors and Check for Active Diagnostic Codes

  1. Disconnect the following sensors one at a time. Wait for 15 seconds after you disconnect each sensor. Check for the active 262-04 diagnostic code again.

    • Injection actuation pressure sensor

    • Boost pressure sensor

    • Atmospheric pressure sensor

    • Fuel pressure sensor

    • Engine oil pressure sensor

    • Auxiliary pressure sensor

Expected Result:

The 262-04 diagnostic code deactivates when a particular sensor is disconnected.

Results:

  • OK - The 262-04 diagnostic code deactivates when a particular sensor is disconnected.

    Repair: Connect the suspect sensor. If the code returns, replace the sensor.Connect all of the connectors. Verify that the problem is resolved.

    STOP

  • Not OK - The 262-04 diagnostic code remains after all of the sensors are disconnected. Leave the sensors disconnected. Proceed to Test Step 5.

Test Step 5. Check the +5 V Supply Wire for a Short

  1. Turn the keyswitch to the OFF position.

  1. Disconnect the J2/P2 ECM connector. Disconnect the J1/P1 ECM connector.

  1. Verify that all of the pressure sensors are disconnected.

    Note: Wiggle the harness during the following measurements in order to reveal an intermittent condition.

  1. Measure the resistance between terminal P2-2 (+5 V Supply) and all of the other terminals on the P2 connector.

  1. Measure the resistance between terminal P2-2 and the engine ground.

  1. Measure the resistance between terminal P1-2 (+5 V Supply) and all of the remaining terminals on the P1 connector.

  1. Measure the resistance between terminal P1-2 and the engine ground.

Expected Result:

Each resistance measurement indicates an open circuit.

Results:

  • OK - Each resistance measurement indicates an open circuit. Proceed to Test Step 6.

  • Not OK - At least one of the resistance measurements does not indicate an open circuit. A +5 V supply wire has a short circuit. There may be a problem with a connector.

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

    STOP

Test Step 6. Check the +5 V Supply and the Sensor Common for an Open Circuit

  1. Install a wire jumper between terminals P2-2 (+5 V Supply) and P2-3 (Sensor Common).

  1. Install a wire jumper between terminals P1-2 (+5 V Supply) and P1-3 (Sensor Common).

    Note: Wiggle the harness during the following measurements in order to reveal any intermittent short condition.

  1. Measure the resistance between terminals A and B at the harness connector for each pressure sensor.

Expected Result:

Each resistance measurement is less than ten Ohms.

Results:

  • OK - Each measurement is less than ten Ohms. There is no open circuit. Proceed to Test Step 7.

  • Not OK - At least one resistance measurement is greater than ten Ohms. The +5 V supply wire or the return wire has an open circuit. There may be a problem in a connector.

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

    STOP

Test Step 7. Check the +5 V Supply at the ECM

  1. Remove terminal 2 (+5 V Supply) from the P2 connector. Install a wire jumper with socket terminals on both ends into P2-2.

  1. Connect ECM connectors J2/P2.

  1. Remove terminal 2 (+5 V Supply) from the P1 connector. Install a wire jumper with socket terminals on both ends into P1-2.

  1. Connect ECM connectors J1/P1.

  1. Turn the keyswitch to the ON position.

  1. Measure the voltage between the wire jumper in P1-2 and the engine ground.

  1. Measure the voltage between the wire jumper in P2-2 and the engine ground.

  1. Turn the keyswitch to the OFF position.

  1. Restore both wires to the original configuration.

Expected Result:

Both voltage measurements are 5.0 ± 0.2 VDC.

Results:

  • OK - Both voltage measurements are 5.0 ± 0.2 VDC. The ECM is OK.

    Repair: Clear all diagnostic codes. Check for active diagnostic codes. If the problem is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".

    STOP

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

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

    STOP

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