A problem Volvo owners experience is an error message on dashboard stating AWD Disabled - Service Required. This problem is often due to issues with the Differential Electronic Module (DEM) or a blown fuse or defective Volvo AOC pump. This problem affects models with AWD including Volvo XC90 XC70 V70 S60 S80 S40.
What makes Volvo different from most all-wheel-drive systems is that all four wheels are not permanently driven. Volvo AWD system is engaged by the Differential Electronic Module (DEM) located under the vehicle when needed.
Under regular driving circumstances, only the front wheels are driven. When wheel slippage is detected, the computer control unit redirects torque to the rear wheels to compensate for the loss of traction at the front.
- AWD Light On
- AWD Disabled - Service Required Warning
- No communication with DEM module
- Related Fault Codes
- DEM0005 Control Valve Internal Fault
- DEM0006 Haldex Pump Bad / Feed pump faulty signal
- DEM0007 Pressure Sensor Defective
AWD Disabled Service Required message on the dashboard is the first thing you notice. In some cases, this message comes on in conjunction with DTSC or anti-skid system warnings.
As the system is not permanently on, it is possible at that you don’t notice that the system hasn't been working for a long time.
Common problems with Volvo AWD system include:
Volvo DEM module is installed under the vehicle by the differential and is prone to corrosion and water damage. Mounted in the rear axle they are exposed to elements. This can lead to the casing and electric board corrosion, which usually causes malfunction.
Common symptoms include no communication with module when you read Diagnostic Trouble Codes (DTC) codes. Once you loose communication with the DEM module the AWD message will come on.
Codes: P0960, P0961, P0962 or P0606.
Another possible failure is a defective Volvo AOC pump. This can be caused by age and wear, but it can also be a result of a blocked oil filter. In addition to pump renewal, make sure you replace Volvo AOC filter and oil. The reason for Volvo AWD system pump failure is lack of service. Volvo official maintenance routines do not state any service intervals regarding this item, calling them a “fitted for life” or “non-serviceable item”.
Code: P1889 - oil pressure pump performance.
Intermittent ‘AWD Malfunction’ warning on the dashboard, combined with AWD sporadically not working is usually caused by blocked filters. In real life, filters can get clogged as early as 50,000 miles due to clutch material clogging the filter. This causes pump failure. The problem may start with the pump fuse that keeps blowing. Replacing oil and filter every 30k miles or 3 years is recommended to avoid this problem.
Problems with the electrical system, either a flat battery or an overcharging alternator, can also trigger an AWD related codes, such as P0562 or P0562. Simply deleting them solves the problem in most cases.
Damaged wires or corroded terminals can cause no communication Differential Electronic Module as well.
Troubleshooting Volvo AWD Problems
- Clean Connections - Check and clean all electrical connections at the rear differential, DEM, pump, pressure-sensor.
- Fuse - Check the fuse for AWD / DEM typically a 7.5A labeled as fuse 17 or 23 in the Rear Electronic Module (REM).
- Replace Volvo Haldex Oil and Filter.
- If the DEM module is defective it will be repaired or replaced. As with any other problem, there are several solutions. See options in the next section.
- If none of the tips above work, scanning the AWD system for codes is the next recommended step. Be aware that not all aftermarket Volvo diagnostic scanners communicate with the Haldex AWD ECU.
Volvo DEM Failure / Possible Repairs
If you have a defective DEM module, you will need to replace or repair it.
Here are some options.
- Repair existing DEM Module - You can get your DEM module remanufactured by a specialist. Haldex system has a wide range of applications, and as this problems are fairly common, there are a number of specialists that offer this service. Not only that the remanufactured DEM module offers a considerably lower price than a new one , it also does not need to be reprogrammed. The only real drawback is that the remanufacturing process takes 4-10 days. Remove your DEM module and ship it to a specialist that offers Volvo DEM Repair Service.
- Dealer Repair - Installing a new DEM module is an obvious and easiest solution. New module needs to be programmed, and this is best done by a dealer. As one might imagine, this is by far the most expensive option. At a Volvo dealership, DEM module replacement costs $1000+.
- Used DEM Module - Acquiring a working used DEM module might seem as a cheaper option, but they can be hard to find. And, as with any used part, you might end up with a part that will fail soon.
Understand Volvo Haldex AWD system
If you are looking to underestand Volvo Haldex AWD problems it is important to point out that there are several generations of Haldex AWD system.
- Generation 1, from 1998 - this system utilizes an electronically controlled hydraulic-mechanical All-Wheel-Drive concept, which attempts to engage the rear wheels when the front wheels start to slip.
- Generation 2, from 2001 - is an electronically controlled permanent 4x4 system with an automatic power distribution between the front and rear wheels. This depends on the road conditions, but normally 95% of the power goes to the front wheels. It was used in Volvo XC70 and XC90.
- Generation 3, from 2006 - this system is aimed at providing a more immediate off-road response. As electronics can pre-tension the clutch and activate all wheel drive before a wheel slip occurs, it provides enhanced capabilities It is installed in most Volvo cars from those ages.
- Generation 4, from 2008 - is similar in function to generation 3, with some changes regarding the pump type.
- Volvo Haldex AWD Differential Electronic Module, Pump and Filter Removal Procedure by XeMODex Inc
- Volvo AOC Pump Replacement on Swedespeed Forum posted by Volvo Owner
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