879172106 Mercruiser SENSOR

Illustration 1 g00770278
SchematicTest Step 1. Inspect Electrical Connectors and Wiring.
Turn the keyswitch to the OFF/RESET position.
Thoroughly inspect ECM connector J1/P1, machine connector J3/P3, and all other connectors in the wiring harness. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.Expected Result:All connectors, pins, and sockets are completely inserted and coupled. The harness and wiring are free of corrosion, of abrasion, and of pinch points. All connections and grounds are tight and free of corrosion.Results:
OK - Proceed to Test Step 2.
Not OK - Repair: Repair the circuit.Verify that the repair eliminates the problem.STOPTest Step 2. Check for Shorts in the Harness.
Illustration 2 g00678938
ECM connector P1 (ECM side)
Disconnect ECM connector J1/P1 and all of the analog sensors.
Measure the resistance between P1:36 (Analog Sensor +5V) and P1:30 (Analog Sensor Return).
Measure the resistance between P1:36 (Analog Sensor +5V) and engine ground.Expected Result:The resistance is greater than 20,000 Ohms.Results:
OK - Proceed to Test Step 3.
Not OK - There is a short between the ECM and the analog sensors.Repair: Repair the circuit.Verify that the repair eliminates the problem.STOPTest Step 3. Check the Analog Sensor Supply Voltage at the Sensor Connectors.
Reconnect ECM connector J1/P1.
Turn the keyswitch to the ON position.
Measure the voltage across terminal A (+5V Analog) and terminal B (Analog Return) at the harness side of each sensor connector.Expected Result:The analog sensor supply voltage is 5.0 0.5 VDC at each sensor connector.Results:
OK - The supply voltage is reaching the sensors. Proceed to Test Step 4.
Not OK - The supply voltage is not reaching the sensors. Proceed to Test Step 5.Test Step 4. Check the Analog Sensors for Internal Shorts.
Illustration 3 g00678938
J1/P1 breakout
Turn the keyswitch to the OFF/RESET position and install a 7X-1715 Adapter Cable at ECM connector J1/P1.
Disconnect all of the analog sensors.
Turn the keyswitch to the ON position.
Measure the voltage across P1:36 (Analog Sensor +5V) and P1:30 (Analog Sensor Return) at the breakout.
Connect each analog sensor individually, while you monitor the supply voltage across P1:36 (Analog Sensor +5V) and P1:30 (Analog Sensor Return) at the breakout.Expected Result:The analog sensor supply voltage is 5.0 0.5 VDC. The voltage should not drop when the sensors are connected.Results:
OK - None of the analog sensors are internally shorted and there is not a problem with the analog sensor supply circuit.Repair: Refer to Troubleshooting, "Electrical Connectors - Inspect" if the problem is intermittent.STOP
Not OK - The sensor that pulls down the supply voltage appears to be internally shorted.Repair: Temporarily connect a new sensor.Verify that the replacement sensor solves the problem before you permanently install the new sensor.STOPTest Step 5. Check the Analog Sensor Supply Voltage at the ECM.
Illustration 4 g00678938
J1/P1 breakout
Turn the keyswitch to the OFF/RESET position and install a 7X-1715 Adapter Cable at ECM connector J1/P1.
Turn the keyswitch to the ON position.
Measure the voltage across P1:36 (Analog Sensor +5V) and P1:30 (Analog Sensor Return) at the breakout.Expected Result:The supply voltage is 5.0 0.5 VDC.Results:
OK - The ECM is supplying the correct voltage, but there is an open in the harness between the ECM and the analog sensors.Repair: Repair the circuit.Verify that the repair eliminates the problem.STOP
Not OK - The ECM is not supplying the correct voltage.Repair: Verify your results.Replace the ECM. Refer to Troubleshooting, "Replacing the ECM" before replacing the ECM.Verify that the repair eliminates the problem.STOP