DEM-0001 AWD Not Working

XC70Rider · Post by **XC70Rider** » 13 Jun 2019, 15:28

After reinserting the DEM onto the Haldex I'm now getting the DEM-0001 code which is Temperature Sensor Faulty Signal.

The reason I took the DEM off is I needed to drop the driveshaft once again. CV grease was escaping from the rear CV joint mounted into the Oscillation Damper. I installed a new end cap and re-greased the CV joint. When I first tried installing the DEM yesterday I bent one of the 2 pins feeding the solenoid. I fixed the pin and cleaned everything up. After watching a Xemodex video I installed the DEM differently this time. After extracting some Haldex fluid I pulled the temp sensor and solenoid from the Haldex. I mounted them onto the DEM then slowly inserted the DEM back into the Haldex. After inserting new Haldex Fluid I dropped her and took it for a spin. I could tell AWD was not working on these wet roads so I hooked up VIDA and got the DEM-0001 code.

I took the DEM out a 3rd time and made sure it was clean and the pins where straight. I threw it back onto the Haldex but still no luck. I'm also getting code REM-1D01 (REM internal fault) for the first time but I believe it's coming up because the REM cannot communicate with the DEM? I also cannot communicate to the DEM using VIDA.

I checked the DEM fuse and the REM fuse. Next I'll raise her up and test for voltages feeding the DEM and oil pump via the connectors. If being fed voltage I may try opening up the DEM and check the circuitry.

Would a faulty temp/ pressure cause this issue? If so I may purchase it at FCP

https://www.fcpeuro.com/products/volvo- ... e-30759668

Post by **vtl** » 14 Jun 2019, 06:55

DEM connectors are not soldered to the board, just plugged in mechanically. They don't take any abuse, yours may have lost electrical contact.

Also DEM is not completely water/oil proof, that ruins electronics. I would split the DEM and tried to fix it: clean the oxidized spots, solder connectors using lead solder (this is important for automotive applications), reseal it properly - rubber seal around the connectors does not do any good job.

I'm even thinking of moving DEM to trunk. Spare DEM will be still attached to Haldex, though it would just have connectors for solenoid and temp/pressure sensor and run wires to the real DEM that sits in a dry and cool place.

XC70Rider · Post by **XC70Rider** » 14 Jun 2019, 07:09

vtl wrote: ↑14 Jun 2019, 06:55 DEM connectors are not soldered to the board, just plugged in mechanically. They don't take any abuse, yours may have lost electrical contact.

Also DEM is not completely water/oil proof, that ruins electronics. I would split the DEM and tried to fix it: clean the oxidized spots, solder connectors using lead solder (this is important for automotive applications), reseal it properly - rubber seal around the connectors does not do any good job.

I'm even thinking of moving DEM to trunk. Spare DEM will be still attached to Haldex, though it would just have connectors for solenoid and temp/pressure sensor and run wires to the real DEM that sits in a dry and cool place.

I might of given the DEM too much force during first installation when I bent the pin for the solenoid connection. Might of loosened one of the connectors internally. I'll take it off again today and inspect it.

What sealant do you recommend for the connectors and the back panel?

Thanks again for your assistance VTL.

Post by **vtl** » 14 Jun 2019, 07:19

XC70Rider wrote: ↑14 Jun 2019, 07:09What sealant do you recommend for the connectors and the back panel?

Whatever water- and heat-proof sealant you have in garage. I used a fireplace sealant from Home Depot

Didn't seal the inner connector, simply was not sure how fireplace sealant would react on possible oil breach. On the other hand, if oil breaches, any sealant will hold it away from electronics for a bit.

Also don't seal 3 pressure equalization holes between external connectors! You can see two of them on the shot above (third one I managed to seal

)

XC70Rider · Post by **XC70Rider** » 14 Jun 2019, 07:34

I have plenty of sealants in my drawer but I'll shop for some more while I pick up a soldering iron. My 25 year old Radio Shack soldering iron went defective last week. Sure miss Radio Shack. They made high quality parts decades back.

Thank you!

XC70Rider · Post by **XC70Rider** » 14 Jun 2019, 14:21

XC70Rider wrote: ↑13 Jun 2019, 15:28 .... I also cannot communicate to the DEM using VIDA.

I got communication with the DEM today. Only working with VIDA for several months I'm still learning.

Could only communicate with the pump and not the sensor. Got 0MPa pressure and -54C temp reading from the pressure sensor.

At least I know the DEM isn't bad. I either have a faulty pressure sensor or bad connections with it.

I'll head to the JY tomorrow and pull a sensor and see if it fixes the DEM-0001 DTC.

XC70Rider · Post by **XC70Rider** » 16 Jun 2019, 08:46

vtl wrote: ↑14 Jun 2019, 06:55 DEM connectors are not soldered to the board, just plugged in mechanically. They don't take any abuse, yours may have lost electrical contact.

I was able to communicate to the DEM but got default readings from the sensor. With default readings you predict the sensor is faulty? If there was no connection to the sensor chances are no values would appear.

Until I get it fixed I pulled the DEM 7.5A fuse so the pump doesn't get burnt from being on all the time.

XC70Rider · Post by **XC70Rider** » 16 Jun 2019, 19:16

XC70Rider wrote: ↑16 Jun 2019, 08:46
vtl wrote: ↑14 Jun 2019, 06:55 DEM connectors are not soldered to the board, just plugged in mechanically. They don't take any abuse, yours may have lost electrical contact.

I was able to communicate to the DEM but got out of range readings from the sensor. With the low pressure and low temp readings you predict just the sensor is faulty? If there was no connection to the sensor chances are no values would appear.

Until I get it fixed I pulled the DEM 7.5A fuse so the pump doesn't get burnt from being on all the time.

Those default readings don't change while driving so I predict I lost connection with the sensor. I'll check the sensor pins and the terminal it slides into. The sensor can only be inserted onto the DEM in 1 direction. When I bent the pin on the valve terminal last week I might of caused an internal mis-connection.

Before I open up the DEM I'll fish for a 80 Bar sensor at the JY tomorrow.

XC70Rider · Post by **XC70Rider** » 17 Jun 2019, 12:26

The outer pin on the sensor was broken off. I gave too much force when first installing it last week.

Couldn't find an 80 Bar sensor locally. I did get a 40 Bar sensor. It will read the temperature but not the pressure.

With no pressure reading AWD won't work.

Ordered a new 80 Bar sensor, 30759668, and a new Repair kit, 30783288, for $180 total. I'll pick it up tomorrow morning in Simsbury, CT.

If it fixes the AWD I'll report back tomorrow.

XC70Rider · Post by **XC70Rider** » 19 Jun 2019, 21:01

After installing a brand new 80 bar sensor and repair kit the DEM-0001 cleared but now I'm getting DEM-0007 (hydraulic pressure faulty value). The sensor reads both pressure and temperature. It reads 20C on a cold start then climbs up to 33C after a 15 minute drive.

For some reason the sensor isn't getting any pressure reading. It only reads 0Mpa. The Haldex fluid is full. I tried testing the pump with a 9V battery but got no response. Does it need 12V to turn on? The pump current is reading 2.5 to 7amps. Does that verify the pump is being activated?

The solenoid valve current never varies. Is the solenoid always fed just 6mA? I tested it with a 9V battery and the valve opened.