Nissan Sentra Service Manual: P0643 Sensor power supply

Nissan Sentra Service Manual / Engine / Engine control system / Dtc/circuit diagnosis / P0643 Sensor power supply

Description

ECM supplies a voltage of 5.0 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 shorted-circuit sensor.

Sensor power supply 1

Battery current sensor
Crankshaft position (CKP) sensor (POS)
Throttle position (TP) sensor
Accelerator pedal position (APP) sensor 1

NOTE:

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

Sensor power supply 2

Camshaft position (CMP) sensor (PHASE)
Mass air flow (MAF) sensor
Engine oil pressure (EOP) sensor
Exhaust valve timing (EVT) control position sensor
Accelerator pedal position (APP) sensor 2
Intake manifold runner control valve position sensor

DTC Logic

DTC DETECTION LOGIC

DTC No.	CONSULT screen terms (Trouble diagnosis content)	DTC detecting condition	Possible cause
P0643	SENSOR POWER/CIRC (Sensor reference voltage ″A″ circuit high)	ECM detects that the voltage of sensor power supply 1 is excessively low or high.	Harness or connectors (Battery current sensor circuit is shorted.) (CKP sensor circuit is shorted.) (TP sensor circuit is shorted.) (Refrigerant pressure sensor circuit is shorted.) (APP sensor 1 circuit is shorted.) Battery current sensor CKP sensor TP sensor Refrigerant pressure sensor APP sensor

DTC CONFIRMATION PROCEDURE

1.PRECONDITIONING

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

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

TESTING CONDITION:

Before performing the following procedure, confirm that battery voltage is more than 10 V at idle.

>> GO TO 2.

2.PERFORM DTC CONFIRMATION PROCEDUR

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

Is DTC detected? YES >> Refer to EC-354, "Diagnosis Procedure".

NO >> INSPECTION END

Diagnosis Procedure

1.CHECK ACCELERATOR PEDAL POSITION SENSOR 1 POWER SUPPLY CIRCUIT

Disconnect accelerator pedal position (APP) sensor harness connector.
Turn ignition switch ON.
Check the voltage between APP sensor harness connector and ground.

Is the inspection result normal?

Is the inspection result normal? YES >> GO TO 4.

NO >> GO TO 2.

2.CHECK SENSOR POWER SUPPLY CIRCUITS

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

Is the inspection result normal?

Is the inspection result normal? YES >> GO TO 3.

NO >> Repair short to ground or short to power in harness or connectors.

3.CHECK COMPONENTS

Check the following.

Is the inspection result normal?

Is the inspection result normal? YES >> GO TO 4.

NO >> Repair or replace malfunctioning component.

4.CHECK APP SENSOR

Check APP sensor. Refer to EC-433, "Component Inspection (APP Sensor)".

Is the inspection result normal? YES >> Check intermittent incident. Refer to GI-39, "Intermittent Incident".

NO >> Replace accelerator pedal assembly. Refer to ACC-3, "Removal and Installation".

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