Low Range Gear Monitor

Low Range Gear Monitor

Description
In common with other off-road vehicles, Land Rovers are equipped with a 2-speed transfer box. This provides a high range for use in normal driving conditions and a low range for use in extreme off-road conditions.

During off-road driving conditions, the vehicle may be operated for extended periods at very low engine speeds and high loads. The vehicle may be required to wade through water of varying depth and temperature. There are often sudden shocks to the drive train due to large rocks and similar objects.

In general, off-road operation can be far more varied and less predictable than normal, on-road driving.

Since OBD is primarily designed for passenger cars and passenger car usage patterns, Land Rover have made the engagement of high range an enablement criteria for the following OBD monitors in order to ensure reliable functioning of the OBD system:
^ Purge System
^ Catalyst Monitoring
^ Thermostat Monitoring
^ Idle Speed Control Diagnostics
^ Oxygen Sensor Diagnostics
^ Misfire Detection
^ Fuel System Diagnostics
^ Fuel Tank Level Sensor

The low range gear monitor checks that the actual transfer gear ratio transmitted by the transfer box is consistent with the vehicle speed expected for the current gear ratio. If the vehicle speed is not consistent with that expected for the current transfer low range for a predefined time then a failure is registered.





If the above table does not include details of the following enabling conditions: - IAT, ECT, vehicle speed range, and time after engine start-up then the state of these parameters has no influence upon the execution of the monitor.