Checking Intermittent Four-Wheel Drive

Checking intermittent four-wheel drive

Checking intermittent four-wheel drive

Note! Before troubleshooting of four-wheel drive is performed, the components included in the power transmission shall be checked with regards to mechanical damages.

A working pressure is needed to enable torque transmission to the rear axle. This pressure is built up by the feed pump. The feed pump works in intervals to build up a max. pressure. Then the working pressure is adjusted via a pressure control valve. When the feed pump is not active, the pressure is maintained in the system via an accumulator.
If the clutch has an internal leak or a damaged accumulator then the system will, when the pump is not active, lose the pressure that is needed for the torque to be transmitted. Then the four-wheel drive works intermittently, that is, it works when the feed pump works and does not work when the pump is turned off.
This may be difficult to detect by test-driving. To obtain a meaningful test of this, the following test-driving case can be performed at the same time as "power supply pump motor" is read out in the parameter list under vehicle communication. This is to check that four-wheel drive is available even when the feed pump is not active.
- Test-driving on rollers.
- Start and driving uphill on "slippery" ground.

Note! This failure is not solved by replacing Differential electronic module (DEM), it is solved by replacing clutch four-wheel drive.

Other information:
- Clutch four-wheel drive, B6304T4, TF-80SC AWD Clutch Four-Wheel Drive

Continue - DONE

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