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

Dtc Description

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

Note:

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

DTC

CONSULT screen terms

(Trouble diagnosis content)

DTC detection condition

P0643

SENSOR POWER/CIRC

(Sensor reference voltage “A” circuit high)

Diagnosis condition

Engine running at idle

Signal (terminal)

Sensor power supply 1 signal

Threshold

ECM detects that the voltage of sensor power supply 1 is excessively low or high

Diagnosis delay time

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

Engine operating condition in fail-safe mode

Fail safe mode

Nissan Sentra Vehicle behavior

Device fix mode

  • This mode fixes the electric IVT motor and the EVT control solenoid valve in the reference position.

  • The intake manifold runner control valve motor is turned OFF (intake manifold runner control valve opens).

Others

ECM stops the electric throttle control actuator control, throttle valve is maintained at a fixed opening (approx. 5 degrees) by the return spring.

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

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

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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