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Discussion Starter · #1 · (Edited)
Last Friday at Sepang F1 track, ambient temperature was one of the hottest I've been on the track. At 1pm, it was like 36-37C, at times feels almost like 40C.

After first round of CCT, it happened. "Anti-Skid Service Required".... AWD/4 Wheel function was disengaged

checking DTCs :
DEM-001 Temperature Sensor Faulty Signal
BCM-0095 Communication between control units communication problem with DEM

This is caused by the AWD rear oil temperature to reach 110degrees and therefore the AWD is disengaged to allow it to cool down - wow, not bad, good Volvo Safety feature for parts and driver in case AWD ceased.

Clearing the code 2-3 times in the pits only managed to clear BCM-0095, also did BCM brake calibration and what was left was the DEM-001 code.

BCM cant communicate with DEM? Oouch..
BCM-0095 Communication between control units communication problem with DEM

Well at least after clearing DTC BCM- Brake Control Module can communicate to DEM - one problem solved.


Possible Permanent failure of the Haldex ECU for the AWD aka Haldex ECU DEM Heat Stroke or a fried Haldex ECU from hot ambient temperature, track heat and being close to the exhaust etc.

Further research on the Internet revealed that the DEM-001 is stored in memory for sometime so a couple of code deletion on different interval was required.

Steps taken :

1. Clear DTC several time when car ignition is in postion 2, 3 - 4 time deletion was done.
2. DEM-001 code appears on re-scan, delete it and shut down the car (ignition II to off)
3. Leave the car to cool down overnight
4. Start the car in the morning to let it do the regular morning warm-ups.
5. Shut the engine down after 3-5 minutes
6. Check the DTC codes and the DEM-001 didn't appear (cleared from stored semi-permanent type memory)
7. AWD all working and take it for a spin to do AWD drift to check AWD is working.
8. Off engine and check DTC codes again - no more DEM-001 codes.

Took the car for a 3 hour drive, check DTCs and non appeared, seems to have permanently solved the DEM-001 issue.

Therefore, next time if you get a DEM-001 message code that indicates AWD is disengaged and suspect a fried DEM because DEM-001 indicates some sort of DEM failure, try the above and see if it works out/solves the DEM problem.

Am I glad my DEM wasn't fried, the DEM-001 was pointing in that direction though.

next steps :

1. DEM heat shields and
2. "two Feet DEI Thermal Exhaust wrap" just below DEM. Exhaust wrap to prevent exhaust radiant heat closest to the DEM from exhaust radiant heat


Hope the above information was helpful.


Cheers, LA
 

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BCM-0095 Communication between control units communication problem with DEM

Having this same issue. Was your AWD drive working when you first had symptoms described above.

thanks,
 

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Discussion Starter · #4 ·
You can you use the following to read / delete - Vida, BSR PPC, Rica iSoftloader, IPD's Loader to clear the DTC codes. You can also use the car in-built function to read the DTC codes if a reader isn't readily available.
 

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Discussion Starter · #5 · (Edited)
Yes my AWD was working before the messages.

Assuming you've already checked all physical connection to BCM etc is all intact
1. Try to delete the DTC code in key position 2.
2. Check DTC codes again, if present, delete it.
3. Start the car, drive it for 5 mins, switch it off, check DTC codes again.

If still present, go to your dealer or workshop, use Vida to Calibrate BCM - it should show 5-6 green calibration successful light. As BCM is close to SUM, would suggest fo a quick SUM calibration. With Vida handy, your dealer or someone from your local area can do both BCM and SUM calibration in under a minute.

Then repeat steps 1 to 3. If it clears completely - Yay!, else will need to diagnose it further as it could be purely mechanical at this stage after trying the above.

I did the above steps and BCM-0095 was cleared so I suspect it either has something to do with Brake Calibration, the nees for Sum re-alignment that forced the car system to redo its check and balances of its accessories or the fact that DEM-001 trigerred it.

BCM-0095 Communication between control units communication problem with DEM

Having this same issue. Was your AWD drive working when you first had symptoms described above.

thanks,
 
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