198003718 - 1064BH CHECK ON OPERATION OF SUPERCHARGING AIR BY-PASS SOLENOID VALVE (SHUT OFF)

This is a normally closed solenoid valve and it is opened by a voltage signal from the engine management control unit during the release stage of the accelerator to discharge the counter-pressure that is created between the closed throttle (when the accelerator is released) and the pressure of the turbine when moving, preventing the turbine from stalling, whilst it is closed during the re-acceleration stage or when the engine is idling.

STEP	CHECK TO BE PERFORMED	REMEDIAL ACTION IF THE CHECK IS NOT OK
1	Solenoid valve resistance checkDisconnect the wiring for the solenoid valve. Check that the resistance between the two terminals of the solenoid valve is 14 ohm ±10% at 20 °C (FIG.1).	Replace the by-pass solenoid valve    Op. 1048B58 TURBOCHARGER AIR BY-PASS VALVE - R.R.
2	Solenoid valve operation checkConnect the terminals of the solenoid valve to a 12 volt batteryCheck that the solenoid valve opens and there are no impediments to the flow of air between ducts 1 and 2(internal passage open)	Replace the by-pass solenoid valve    Op. 1048B58 TURBOCHARGER AIR BY-PASS VALVE - R.R.
3	Solenoid valve control signal checkConnect the Examiner in voltmeter mode: red probe to pin 1 of the solenoid valve and black probe to pin 2Set the Examiner basic time at 5 seconds and 20 V f.s.Start the engineRoad test the vehicle (sticking to the speed limits in force) as follows:On an out of town route with 3rd gear engagedInitiate the acquistion by pressing start on the diagnostic equipment and fully depress the accelerator pedal until the engine speed is 4500 rpm.Once this speed is reached completely release the accelerator pedal.Display the resulting graph (acquired during the release of the accelerator pedal) corresponding to the throttle closed stage.	Restore wiring continuityRestore the correct supply by replacing the 15 A fuse F11 after having identified the cause of the malfunction.Replace the engine management control unit if the signal is interrupted at the control unit output    Op. 1056B82 INJECTION/IGNITION SYSTEM E.C.U. (ONE) - R + R

FIG.1: Shut off valveShut off solenoid valve control signal