48132 Mercruiser HOSE, THERMOSTAT HOUSING TO EXHAUST MANIFOLD (FRONT)

The following background information is related to this procedure:The ECM supplies regulated +5 VDC to the following sensors:
Intake manifold air pressure sensor
Fuel rail pressure sensor
Intake throttle valve position sensor (if equipped)
NRS valve position sensor
Camshaft speed/timing sensorA diagnostic code can be caused by the following conditions:
A short circuit in the harness
A faulty sensor
An open circuit in the harness
Illustration 1 g06097792
Schematic for the 5 VDC supply 1
Illustration 2 g06088268
Schematic for the 5 VDC supply 2
Illustration 3 g03834424
Fuel rail pressure sensor
(1) 5 VDC Supply
(3) Ground
Illustration 4 g03834769
Typical example of an engine pressure sensor
(2) Ground
(3) 5 VDC Supply
Illustration 5 g03826056
Connector for the NRS valve
(2) +5 VDC
(3) Ground
Illustration 6 g03826026
Connector for the intake throttle valve (if equipped)
(3) Ground
(5) +5 VDCComplete the procedure in the order in which the steps are listed.
Table 2
Troubleshooting Test Steps Values Results
1. Determine the Code
A. Connect the electronic service tool to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools", if necessary.
B. Turn the keyswitch to the ON position.
C. Determine if a diagnostic trouble code is present.
Diagnostic Codes
Result: A -3 or -4 code is present.
Note which sensor supply has the active diagnostic code.
Proceed to Test Step 2.
2. Check for a Failed Sensor
A. Connect to the electronic service tool.
B. Turn the keyswitch to the ON position.
C. Disconnect a sensor on the suspect sensor supply circuit.
D. Monitor the electronic service tool while the sensor is disconnected to see if the active code changes to logged.
E. Connect the suspect sensor to the wiring harness
F. Repeat steps C through E for each sensor on the suspect sensor supply.
Failed Sensor
Result: The suspect sensor supply active code changes to logged when a sensor is unplugged.
Repair: Replace the failed sensor.
Verify that the repair resolved the fault.
Result: The suspect sensor supply active code remains active after all sensors on the sensor supply circuit have been checked.
Proceed to Test Step 3.
3. Check the Wiring for an Open Circuit
A. Turn the keyswitch to the OFF position.
B. Disconnect all sensors on the suspect 5 VDC supply circuit.
C. Disconnect the engine interface connector.
D. Disconnect the J1 and J2 connector from the ECM, as applicable.
5 VDC Supply Circuit 1
E. Measure the following resistances:
Pin 1 on the fuel rail pressure sensor harness connector to pin 27 on the sensor side of the engine interface connector.
Pin 3 on the fuel rail pressure sensor harness connector to pin 8 on the sensor side of the engine interface connector.
Pin 27 on the ECM side of the engine interface connector to P2:45.
Pin 8 on the ECM side of the engine interface connector to P2:16.
5 VDC Supply Circuit 2
F. Measure the following resistances:
Pin 3 on the intake throttle valve harness connector to pin 5 on the sensor side of the engine interface connector.
Pin 5 on the intake throttle valve harness connector to pin 14 on the sensor side of the engine interface connector.
Pin 5 on the ECM side of the engine interface connector to P2:12.
Pin 14 on the ECM side of the engine interface connector to P2:24.
Pin 2 on the NRS valve harness connector to pin 12 on the sensor side of the engine interface connector.
Pin 3 on the NRS valve harness connector to pin 5 on the sensor side of the engine interface connector.
Pin 12 on the ECM side of the engine interface connector to P2:22.
Pin 2 on the intake manifold air pressure sensor harness connector to pin 6 on the sensor side of the engine interface connector.
Pin 3 on the intake manifold air pressure sensor harness connector to pin 13 on the sensor side of the engine interface connector.
Pin 6 on the ECM side of the engine interface connector to P2:14.
Pin 13 on the ECM side of the engine interface connector to P2:23.
Pin 2 on the camshaft speed/timing sensor harness connect