Nissan Sentra B18 (2020-2025) Service Manual: P0643 Sensor Power Supply

Dtc 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

• APP sensor 1

• Crankshaft position sensor

• EGR volume control valve position sensor

• Exhaust camshaft position sensor

• Intake manifold runner control valve position sensor

• Manifold absolute pressure sensor

• Throttle position sensor

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

Sensor power supply 2

• APP sensor 2

• Intake camshaft position sensor

• Engine oil pressure sensor

• Fuel rail pressure sensor

• Mass air flow sensor

• Refrigerant pressure sensor

DTC DETECTION LOGIC

POSSIBLE CAUSE

• Harness or connectors

  • APP sensor 1 circuit is shorted.

  • Crankshaft position sensor circuit is shorted.

  • EGR volume control valve position sensor circuit is shorted.

  • Exhaust camshaft position sensor circuit is shorted.

  • Intake manifold runner control valve position sensor circuit is shorted.

  • Manifold absolute pressure sensor circuit is shorted.

  • TP sensor circuit is shorted.

• Accelerator pedal position sensor

• Crankshaft position sensor

• EGR volume control valve position sensor

• Exhaust camshaft position sensor

• Intake manifold runner control valve position sensor

• Manifold absolute pressure sensor

• Throttle position sensor

FAIL-SAFE

Engine Control System

Idle Start/Stop System

When a DTC is detected, the start/stop indicator lamp blinks slowly and the idle start/stop system operation is prohibited.

When ECM detects error while operating the idle start/stop system, ECM restarts the engine.

Confirmation Procedure

1. 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.

2. PERFORM DTC CONFIRMATION PROCEDURE

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

   2. Check DTC.

   Is DTC detected?

   YES >>

   Proceed to DTC Diagnosis Procedure.

   NO-1 >>

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

   NO-2 >>

   Confirmation after repair: INSPECTION END

Dtc Diagnosis Procedure

1. CHECK ACCELERATOR PEDAL POSITION SENSOR 1 POWER SUPPLY CIRCUIT

   1. Disconnect accelerator pedal position (APP) sensor harness connector.

   2. Turn ignition switch ON.

   3. Check the voltage between APP sensor harness connector and ground.

      +		−	Voltage (Approx.)
      APP sensor
      Connector	Terminal
      E12	4	Ground	5 V

   Is the inspection result normal?

   YES >>

   Proceed to Component Inspection.

   NO >>

   GO TO 2.

2. CHECK SENSOR POWER SUPPLY CIRCUITS

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

   ECM		Sensor
   Connector	Terminal	Name	Connector	Terminal
   F24	21	Crankshaft position sensor	F22*1 F40*2	3
   	28	Exhaust camshaft position sensor	F57	1
   	54	Manifold absolute pressure sensor	F76	1
   F25	83	EGR volume control valve position sensor	F94	3
   		Intake manifold runner control valve position sensor	F29	1
   	95	Throttle position sensor	F7	3
   E16	156	APP sensor 1	E12	4

   *1: Without idle start/stop system

   *2: With idle start/stop system

   Is the inspection result normal?

   YES >>

   GO TO 3.

   NO >>

   Repair or replace malfunctioning part.

3. CHECK COMPONENTS

   Check the following.

   • Crankshaft position sensor Refer to Component Inspection.

   • EGR volume control valve Refer to Component Inspection.

   • Exhaust camshaft position sensor Refer to Component Inspection.

   • Intake manifold runner control valve position sensor Refer to Component Inspection.

   • Manifold absolute pressure sensor Refer to Component Inspection.

   • Throttle position sensor Refer to Component Inspection.

   Is the inspection result normal?

   YES >>

   INSPECTION END

   NO >>

   Repair or replace malfunctioning part.

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