42481 Mercury CHECK VALVE (NOT USED W/SQUARE FUEL PUMP)

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Schematic for the engine pressure sensors
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(1) Turbocharger outlet pressure sensor (2) Atmospheric pressure sensor (3) Engine oil pressure sensor (4) J2/P2 ECM connector (5) J1/P1 ECM connector
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Air cleaner assembly (typical example) (6) Turbocharger inlet pressure sensorTest Step 1. Inspect the Electrical Connectors and the Wiring
Remove electrical power from the ECM.
Thoroughly inspect connectors (2) and (3). Also, thoroughly inspect the connectors for each pressure sensor. Refer to Troubleshooting, "Electrical Connectors - Inspect".
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P2terminal locations (P2-2) +5 V Sensor supply (P2-3) Sensor return (P2-14) Atmospheric pressure sensor (P2-24) Engine oil pressure sensor (P2-40) Turbocharger outlet pressure sensor
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P1 terminal locations (P1-2) +5 V Sensor supply (P1-3) Sensor return (P1-15) Turbocharger inlet pressure sensor
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Sensor connector (Terminal A) +5 V sensor supply (Terminal B) Sensor return (Terminal C) Signal
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connectors and on each of the wires in the pressure sensor connectors.
Check the allen head screw for each ECM connector and the customer connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and wiring for abrasion and for pinch points from the pressure 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 appear to be 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.STOPTest Step 2. Check the Supply Voltage at the Sensor Connector
Remove electrical power from the ECM.
Disconnect the harness connectors for the following sensors:
Engine oil pressure sensor
Turbocharger outlet pressure sensor
Atmospheric pressure sensor
Turbocharger inlet pressure sensor
Restore electrical power to the ECM.Note: The original diagnostic code may not stay active. An open circuit diagnostic code for the sensor supply may become active when all of the sensors are disconnected. Ignore the active codes at this time and continue with this test step.Note: Be sure to wiggle the harness during the following measurements in order to reveal an intermittent condition.
Measure the voltage between terminals A and B at each sensor connector on the engine harness.
Remove electrical power from the ECM.
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. The voltage is correct at the sensor connectors. Proceed to Test Step 3.
Not OK - At least one voltage measurement is not 5.0 0.2 VDC.Repair: Refer to Troubleshooting, "5 Volt Engine Pressure Sensor Supply Circuit - Test".STOPTest Step 3. Check for Active Diagnostic Codes
Connect Caterpillar Electronic Technician (ET) to the service tool connector.
Restore electrical power to the ECM.
Monitor the active diagnostic code screen on Cat ET. Look for an active diagnostic code for an engine pressure sensor.Note: Wait at least 30 seconds so that any codes may become active.
Determine if the problem is related to an open circuit diagnostic code (03) or a short circuit diagnostic code (04).Expected Result:No diagnostic codes are active.Results:
OK - No diagnostic codes are active for the engine pressure sensors.Repair: The original problem seems to be resolved. The problem may have been related to a faulty connection in the harness. Carefully reinspect the connectors and wiring. If an intermittent electrical problem is suspected, refer to Troubleshooting, "Electrical Connectors - Inspect".STOP
Not OK - A 03 diagnostic code is active at this time. The ECM is detecting an open circuit co