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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. |
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STEP |
CHECK TO BE PERFORMED |
REMEDIAL ACTION IF THE CHECK IS NOT OK |
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1 |
Solenoid valve resistance check Disconnect the wiring from the solenoid. Check that the resistance between the two solenoid terminals is 14 ohm ±10% at 20 °C (FIG. 1) |
Replace the by-pass solenoid valve |
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2 |
Solenoid valve operation check Connect the terminals of the solenoid valve to a 12 volt battery Check 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 |
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3 |
Solenoid valve control signal check Connect the Examiner in voltmeter mode: red probe to pin 1 of the solenoid valve and black probe to pin 2 Set the Examiner basic time at 5 seconds and 20 V f.s. Start the engine Road test the vehicle (respecting the speed limits in force) as follows: On an out of town route with 3rd gear engaged Initiate 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 continuity Restore 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 |
FIG.1: Shut off valve
Shut off solenoid valve control signal