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Home >> Volvo >> 2005 >> XC90 AWD L5-2.5L Turbo VIN 59 B5254T2 >> Repair and Diagnosis >> Transmission and Drivetrain >> Differential Assembly >> Differential Lock >> Testing and Inspection >> Symptom Related Diagnostic Procedures >> Checking the Four Wheel Drive

Checking the Four Wheel Drive






Checking the four wheel drive

Function test

Caution! The test must be carried out on a raised vehicle so that all four wheels are free to turn, with attachment a long way out on the link arms, so as not to damage the drive shafts.

Warning! Ensure that the vehicle is safely raised. Check that no objects are caught in the tire treads.

Note! If the vehicle has STC or DSTC, the function must be de-activated. Depress the STC/DSTC button on the centre console and hold it down for more than 2 seconds. The LED on the button should switch off. If the vehicle has TRACS, this function must also be deactivated. This is done by removing the fuse for the ABS unit from the engine compartment electrical centre. Note that this will cause trouble codes to be set in the Brake Control Module (BCM). These codes must be erased before the vehicle is returned to the customer.

- Ignition off
- Raise the vehicle so that all the driving wheels are hanging free.
- Push down the brake pedal.
- Move the gear selector lever to the P position.
- Start the engine and release the hand brake.
- Move the gear selector lever to the D position.
- Release the brake pedal whilst the engine is idling. If at least one wheel on each axle rotates, verify that both the AOC clutch and its feed pump are active. Make a note of any malfunction. If the front wheels rotate at normal speed but the rear wheels do not rotate this means that the AOC clutch is not functioning correctly. Make a note of any malfunction.
- Push down the accelerator pedal and hold a speed of about 60-80 km/h. Check that all the wheels rotate at the same speed.
- Release the accelerator pedal.
- Position the gear selector lever in the N position immediately after releasing the accelerator pedal.
- Pull on the hand brake whilst the wheels are still rotating and a speed of 60-80 km/h is indicated. Check that the rear wheels stop immediately and that the front wheels continue to rotate. If this is so, then the rapid opening function of the control valve is operating correctly. Make a note of any malfunction. If all the wheels stop rapidly when the hand brake is applied then the valve control is not working correctly. This may be due to a fault in the AOC clutch. Make a note of any malfunction.
- Release the hand brake and depress the brake pedal. All the wheels should stop.
- Position the gear selector lever in the D position.
- Release the brake pedal.

Continue - Function test

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Function test

Caution! The test must be carried out on a raised vehicle so that all four wheels are free to turn, with attachment a long way out on the link arms, so as not to damage the drive shafts.

Warning! Ensure that the vehicle is safely raised. Check that no objects are caught in the tire treads.

Note! The STC/DSTC function is deactivated.

- Ignition off
- Raise the vehicle so that all the driving wheels are hanging free.
- Push down the brake pedal.
- Move the gear selector lever to the P position.
- Start the engine with the hand brake applied. The control lamp in the combination instrument panel should illuminate.
- Move the gear selector lever to the D position.
- Release the brake pedal whilst the engine is idling. If the front wheels rotate slowly and the rear wheels are stationary the AOC clutch is OK. If the front wheels rotate at normal speed whilst the back wheels are stationary then, if the oil level is correct and no fault was found in the previous test, the Differential Electronic Module (DEM) must be replaced.

Other information:
- Differential electronic module (DEM), replacement Service and Repair
- Test driving Active on Demand Coupling, manual transmission, M66 AWD Test Driving Active On Demand Coupling, Manual Transmission
- Test driving Active on Demand Coupling, automatic transmission, TF-80SC AWD, AW50/51 AWD Test Driving Active On Demand Coupling, Automatic Transmission

Was the function OK?

Yes - Function test

No - FAULT FOUND

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Function test

Caution! The test must be carried out on a raised vehicle so that all four wheels are free to turn, with attachment a long way out on the link arms, so as not to damage the drive shafts.

Warning! Ensure that the vehicle is safely raised. Check that no objects are caught in the tire treads.

Note! The STC/DSTC function is deactivated.

- Ignition off
- Raise the vehicle so that all the driving wheels are hanging free.
- Move the gear selector lever to the N position.
- Start the engine with the hand brake applied.
- Let the engine idle whilst attempting to rotate by hand both the front wheels.

Note! The base function of the AOC clutch and the function of its feed pump are verified by checking whether the braking effect on the rear wheels also brakes the front wheels.

- Unplug the 2-pin connector between the Differential Electronic Module (DEM) and the feed pump.
- The gradual sinking of the base pressure is apparent as the base torque diminishes and eventually ceases.
- Plug in the connector between the Differential Electronic Module (DEM) and the feed pump.
- The increase in the base pressure in the clutch is made apparent by the braking of the front wheels via the AOC clutch.
- Unplug the 8 pin connector between the Differential Electronic Module (DEM) and the cable from the vehicle.

Note! When the power supply to the Differential Electronic Module (DEM) is removed the regulator valve will open rapidly. This is verified by the immediate cessation of the base torque.

- Plug in the connector to the Differential Electronic Module (DEM)
- Note that the feed pump to the AOC clutch starts. It can be heard that the pump runs at a higher speed when starting.
- Switch of the engine and leave the ignition on.
- Leave the hand brake on and the gear selector lever in the N position.
- The AOC clutch feed pump should not rotate under these conditions.
When the base pressure function of the AOC clutch and the function of the feed pump have been verified and the tests are OK, replace the AOC clutch.
When the base pressure function of the AOC clutch and the function of the feed pump have been verified and the tests are not OK, replace the Differential Electronic Module (DEM).

Other information
- Active on Demand Coupling (AOC), replacing Service and Repair
- Differential electronic module (DEM), replacement Service and Repair
- Test driving Active on Demand Coupling, manual transmission, M66 AWD Test Driving Active On Demand Coupling, Manual Transmission
- Test driving Active on Demand Coupling, automatic transmission, TF-80SC AWD, AW50/51 AWD Test Driving Active On Demand Coupling, Automatic Transmission

Was a fault detected?

Yes - FAULT FOUND

No - No Fault Found

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