Nissan Sentra Service Manual: P0506 ISC System

Nissan Sentra Service Manual / Engine / Engine control system / Dtc/circuit diagnosis / P0506 ISC System

Description

The ECM controls the engine idle speed to a specified level through the fine adjustment of the air, which is let into the intake manifold, by operating the electric throttle control actuator. The operating of the throttle valve is varied to allow for optimum control of the engine idling speed. The crankshaft position sensor (POS) detects the actual engine speed and sends a signal to the ECM.

The ECM controls the electric throttle control actuator so that the engine speed coincides with the target value memorized in the ECM. The target engine speed is the lowest speed at which the engine can operate steadily.

The optimum value stored in the ECM is determined by taking into consideration various engine conditions, such as during warming up, deceleration, and engine load (air conditioner, power steering and cooling fan operation, etc.).

DTC Logic

DTC DETECTION LOGIC

NOTE:

If DTC P0506 is displayed with other DTC, first perform the trouble diagnosis for the other DTC.

DTC No.	CONSULT screen terms (Trouble diagnosis content)	DTC detecting condition	Possible cause
P0506	ISC SYSTEM (Idle air control system RPM lower than expected)	The idle speed is less than the target idle speed by 100 rpm or more.	Electric throttle control actuator Intake air leak

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.

If the target idle speed is out of the specified value, performEC-140, "Work Procedure", before conducting DTC Confirmation Procedure.

TESTING CONDITION:

Before performing the following procedure, confirm that battery voltage is more than 11 V at idle.
Always perform the test at a temperature above −10В°C (14В°F).

>> GO TO 2.

2.PERFORM DTC CONFIRMATION PROCEDURE

Start engine and warm it up to normal operating temperature.
Turn ignition switch OFF and wait at least 10 seconds.
Start engine and run it for at least 1 minute at idle speed.
Check 1st trip DTC.

Is 1st trip DTC detected? YES >> Proceed to EC-334, "Diagnosis Procedure".

NO >> INSPECTION END

Diagnosis Procedure

1.CHECK INTAKE AIR LEAK

Start engine and let it idle.
Listen for an intake air leak after the mass air flow sensor.

Is intake air leak detected? YES >> Discover air leak location and repair.

NO >> Replace ECM. Refer to EC-485, "Removal and Installation".

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System description
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