Checking Variable Intake System (V-VIS)

CHECKING VARIABLE INTAKE SYSTEM (V-VIS)





Conditions for Fault Tracing:
^ No DTCs present.
^ Fault is permanent.

Fault Sources:
^ Open-circuit in supply or signal lead.
^ Signal lead short-circuited to ground or supply.
^ Contact resistance or oxidation in connector.
^ Faulty vacuum system.

TESTING PROCEDURE





Checking Solenoid Valve
^ Switch ON ignition.
^ Activate Ignition System Diagnostic Test Mode 3.

See: COMPUTERS AND CONTROL SYSTEMS / TESTING AND INSPECTION / OUTPUT DEVICE TEST - DIAGNOSTIC TEST MODE 3 / IGNITION SYSTEM.

Place hand on solenoid valve and check if valve is ticking (i.e. operating).

If valve is ticking:
- Proceed to: Checking Vacuum System, section below.
If valve is not ticking:
- Proceed to: Checking Power Supply.





Checking Power Supply
^ Switch ON ignition.
^ Disconnect solenoid valve.
^ Connect voltmeter between supply connector terminal 2 and ground.

Instrument should indicate battery voltage.

If reading is correct:
- Proceed to: Checking Signal Lead.
If reading is incorrect:
- Check lead between fuse No. 4, terminal 1 and solenoid valve connector terminal 2 for open-circuit.





Checking Signal Lead
^ Switch OFF ignition.
^ Connect test box to Distributor Ignition (DI) System and check ground terminals.
^ Disconnect solenoid valve.
^ Switch ON ignition.
^ Connect voltmeter across #38 (ICM B8) and #20 (ICM A20) on test box.

Instrument should indicate approx. 0 Volts.

If reading is correct:
- Proceed to: Checking Resistance of Signal Lead.
If reading is incorrect:
- Check lead between ICM B8 and solenoid valve connector terminal 1 for short-circuit to ground.





Checking Resistance of Signal Lead
^ Switch OFF ignition.
^ Disconnect Ignition Control Module (ICM).
^ Disconnect solenoid valve.
^ Connect ohmmeter between #38 (ICM B8) on test box and solenoid valve connector terminal 1.

Instrument should indicate approx. 0 Ohms.

If reading is correct:
- Proceed to: Checking Resistance of Signal Lead to Ground.
If reading is incorrect:
- Check lead between ICM B8 and solenoid valve connector terminal 1 for open-circuit.





Checking Resistance of Signal Lead to Ground
^ Switch OFF ignition.
^ Disconnect ICM.
^ Disconnect solenoid valve.
^ Connect ohmmeter between #38 (ICM B8) and #20 (ICM A20) on test box.

Instrument should indicate infinite resistance.

If reading is correct:
- Proceed to: Checking Solenoid Valve.
If reading is incorrect:
- Check lead between ICM B8 and solenoid valve connector terminal 1 for short-circuit to ground.





Checking Solenoid Valve
^ Switch OFF ignition.
^ Reconnect ICM.
^ Reconnect solenoid valve.
^ Switch ON ignition.
^ Activate Ignition System Diagnostic Test Mode 3.

See: COMPUTERS AND CONTROL SYSTEMS / TESTING AND INSPECTION / OUTPUT DEVICE TEST - DIAGNOSTIC TEST MODE 3 / IGNITION SYSTEM.

Place hand on solenoid valve and check if valve is ticking (i.e. operating).

If valve is ticking:
- Fault is due to poor connection in ICM or solenoid valve connector.
- Check connectors for contact resistance and oxidation.
If valve is not ticking:
- Try with new solenoid valve.





Checking Vacuum System
^ START engine and allow to run for approx. 10 seconds.
^ Switch OFF engine.
^ Switch ON ignition.
^ Activate Ignition System Diagnostic Test Mode 3.

See: COMPUTERS AND CONTROL SYSTEMS / TESTING AND INSPECTION / OUTPUT DEVICE TEST - DIAGNOSTIC TEST MODE 3 / IGNITION SYSTEM.

Check that vacuum servo linkage moves 2 - 4 times when solenoid valve ticks (operates).

If linkage moves:
- System is operating correctly.
If linkage does not move:
- Proceed to: Checking Vacuum Servo.





Checking Vacuum Servo
^ Switch OFF ignition.
^ Carefully disconnect black hose from solenoid valve.
^ Connect vacuum pump to black hose.
^ Pump up vacuum (max. 30 kPa / 4.5 psi).

Check if vacuum servo linkage moves and vacuum pump maintains vacuum.

If servo linkage moves and pump maintains vacuum:
- Check vacuum hoses, vacuum tank, solenoid valve hose connections and non-return valve for leakage and/or blockage.
If servo linkage moves but pump loses vacuum:
- Check black hose for leakage.
If hose leaks:
- Try with new hose.
If hose is intact:
- Try with new vacuum servo.
If servo linkage does not move but pump maintains vacuum:
- Check black hose for blockage.
- Clean as required.
If hose is intact:
- Check that vacuum servo linkage is not sticking or seized.
- Clean and lubricate linkage.