Engine - Variable Intake System Troubleshooting Tips

TA02 1901

October 30, 2002

ATTENTION:
Service Manager
Service Advisor
Technician

Troubleshooting Freelander VIS Motor Faults

Variable Intake System (VIS) motor troubleshooting requires an understanding of the logic employed by the Engine Management System to set fault codes. The Technical HelpLine continues to field questions relating to VIS motors that a logical troubleshooting process should resolve.

^ It is important to understand that VIS motor P-codes do not set a MIL illumination. Any MIL event will be due to the presence of other P-codes/faults.

^ VIS motor P-codes can be stored by the ECU for many occurrence of non-response from the VIS motors - even a one-time event. The presence of a VIS P-code does not necessarily mean that the VIS motor is permanently disabled. The motor has internal self-protection circuitry that is able to re-set automatically from a single event.

^ The presence of oil in the intake manifold/VIS motor is not a contributory factor to motor malfunction and should not be a reason for motor replacement. The motors have been tested with extreme levels of oil contamination and continue to function as intended.

When diagnosing VIS motor fault codes make sure the following steps are followed:

^ Note all VIS motor related P-codes.

^ Resolve the causes for other non-VIS motor P-code faults.

^ Clear all codes.

^ Drive the vehicle.
(Follow Discovery Series II cycle "B" or Freelander Cycle "B" when published.)

^ Once the drive cycle is completed, check for stored VIS motor P-codes.

If no VIS fault code has been flagged, the originally observed code can be considered as "historic" and the vehicle can be released.

If a VIS fault is logged, but is undetected by the driver AND differs from the faults originally detected, then the code should be cleared and the vehicle released.

If the same VIS fault is logged in the drive as the code recorded above, the VIS fault must be considered "current" and the motor replaced before release to the customer.

If a vehicle is brought in without a Check Engine light illuminated, but where the customer complains of noticeable change to the engine performance AND the presence of a VIS P-code is verified, the VIS motor should also be changed.

NOTE:
When troubleshooting VIS motor P-codes it is essential to determine if the fault is "current" or "historic". Historic VIS faults will have "self-healed", but those determined to be "current" faults will require component replacement.