Nissan Murano: Dtc/circuit Diagnosis / P0643 Sensor Power Supply

DTC Description

DESCRIPTION

ECM supplies a voltage of 5 V to some of the sensors systematically divided into 2 groups, respectively. Accordingly, when a short circuit develops in a sensor power source, a malfunction may occur simultaneously in the sensors belonging to the same group as the short-circuited sensor.

Sensor power supply 1

• Accelerator pedal position (APP) sensor 1

• Crankshaft position (CKP) sensor (POS)

• Exhaust valve timing (EVT) control position sensor

• Mass air flow (MAF) sensor

• Throttle position (TP) sensor

NOTE:

If sensor power supply 1 circuit is malfunctioning, DTC P0643 is displayed.

Sensor power supply 2

• Accelerator pedal position (APP) sensor 2

• Camshaft position (CMP) sensor (PHASE)

• Engine oil pressure (EOP) sensor

• Refrigerant pressure sensor

DTC DETECTION LOGIC

ECM detects a voltage of power source for sensor is excessively low or high

POSSIBLE CAUSE

• Sensor power supply 1 circuit

  • Accelerator pedal position (APP) sensor 1

  • Crankshaft position (CKP) sensor (POS)

  • Exhaust valve timing (EVT) control position sensor

  • Mass air flow (MAF) sensor

  • Throttle position (TP) sensor

FAIL-SAFE

PRECONDITIONING

If DTC Confirmation Procedure has been previously conducted, always perform the following procedure before conducting the next test.

1. Turn ignition switch OFF and wait at least 10 seconds.

2. Turn ignition switch ON.

3. Turn ignition switch OFF and wait at least 10 seconds.

TESTING CONDITION:

Before performing the following procedure, confirm that battery voltage is more than 8 V at idle.

GO TO 2.

PERFORM DTC CONFIRMATION PROCEDURE

1. Start the engine and let it idle for 1 second.

2. Check DTC.

Is DTC detected?

Proceed to Diagnosis Procedure.

To check malfunction symptom before repair: Refer to Intermittent Incident.

Confirmation after repair: INSPECTION END

CHECK SENSOR POWER SUPPLY 1

1. Ignition switch OFF.

2. Disconnect ECM harness connector.

3. Ignition switch ON.

4. Check the voltage between ECM harness connector and ground.

   +		−	Voltage (Approx.)
   ECM
   Connector	Terminal
   E32	146	Ground	5 V
   F78	28
   F79	98

Is the inspection result normal?

Inspection End.

GO TO 2.

CHECK SENSOR POWER SUPPLY 1 CIRCUIT

1. Ignition switch OFF.

2. Disconnect following sensor harness connector.

3. Check harness for short to power and to ground, between the following terminals.

Is the inspection result normal?

GO TO 3.

Repair or replace error-detected parts.

CHECK COMPONENTS

Check the following.

• Accelerator pedal position (APP) sensor 1 (Refer to Component Inspection.)

• Crankshaft position (CKP) sensor (POS) (Refer to Component Inspection.)

• Exhaust valve timing (EVT) control position sensor [Refer to Component Inspection (Exhaust Valve Timing Control Position Sensor).]

• Mass air flow (MAF) sensor (Refer to Component Inspection.)

• Throttle position (TP) sensor (Refer to Component Inspection.)

Is the inspection result normal?

Inspection End.

Replace malfunctioning component.