2005 XC70 in limp mode and no speedo, tach, temp. gage.

cbova · Post by **cbova** » 26 Feb 2022, 19:17

My Daughter is driving a 2005 XC70 with 184,xxx miles. On Wednesday after 2 hours and 15 minutes of a 2 and a half hour ride (~35°F and raining) it lost tach, speedo, temp gage, and she got CEL, "brake failure, stop safely", "SRS service required", "Service engine system...", ABS, and BRAKE lights. Car went into limp mode and stayed in 3rd gear with no PRDNL display. Heat worked fine but blower speed was high only. All lights and signals worked. When the car was turned off and restarted everything works normal for 5 or so minutes then same deal. It did this twice on Thursday, and once on Friday. I trailered it home yesterday (we were on vacation) got it inside today and pulled the codes. I have the CarSoft i906 so I can see all the modules. It had TON of codes, see below. I suspected either ABS module or CEM based on some preliminary searches. Today I cleared the codes, removed the ABS and CEM for inspection and saw no signs of water intrusion. I decided to put it back together and take it for a road test. Put 40 miles on it, ran like a top. This car has occasionally given me an SRS code or a Service engine system, or a Service transmission error. Usually when it's sub zero cold and I would just clear them and it was fine. I had a few low voltage codes too so I replaced the battery (new OEM Volvo) a few months ago. I have tried to follow the Xemodex trouble shooting flow charts but with everything working today I didn't make any headway. I plan on driving to work it this week to see if it comes back. I'm planning on sending the module to Xemodex for repair but I'd like to have some level of confidence in which module is the culprit. I'm leaning toward the ABS/BCM based on symptoms I've seen but hard to say when everything is working.

Here are the codes I pulled (I'm sure some are old and/or unrelated);
p0700
p0503
p0863
u0002
p0600
aum-46fe
dem0006
ccm-0060
ccm-0064
ccm-0062
ccm-dd12
ccm-0032
ccm-0036
ccm-e001
psm-001e
rem-8c21
rem-e001
uem-0020
cem-df16
cem-df03
cem-1a61
cem-e000
cem-1a62
cem-df17
cem-1a5f
cem-1a51
cem-1a64
cem-1a54
cem-1a5a
cem-9c03
srs-e001
abs-e003
tcm-e000
ecm-900b

Thanks

Post by **abscate** » 27 Feb 2022, 08:28

You need to clear all those and drive it fir a week checking daily for pending codes to track down what is failing first.

Post by **vtl** » 27 Feb 2022, 09:19

CAN-related error, something spoils high speed bus. Try to unplug DEM (Haldex computer) and see how is it going.

Errors I've got when my DEM quit:

It cracked it opened and found water leak past the seal and oxidation on the PCB. One resistor's pad was completely destroyed, that ruined CAN communication on the whole bus (CAN is a shared bus).

cbova · Post by **cbova** » 27 Feb 2022, 18:40

Yeah, I cleared the codes yesterday and have about 60 miles on it since then driving fine. I forgot to mention this car has never had AWD since I've owned it, never bothered to see if it was the bevel gears or DEM. Starting to wonder if it's the DEM now. The only codes I see today are CEM not seeing communication with DEM and I cannot connect to the DEM today (I could yesterday). Car is not in a fault state right now.

Will the car run with the DEM unplugged? I'll see if I can run through the Xemodex flow chart for the DEM next.

Thanks

Post by **vtl** » 27 Feb 2022, 18:54

It will run.

Post by **erikv11** » 27 Feb 2022, 20:27

Lack of AWD is more often the pump than the DEM but yes, could be.

cbova · Post by **cbova** » 28 Feb 2022, 16:32

So today I still cannot communicate with DEM and I got a "service SRS airbag urgent" warning (text and yellow triangle) but no red airbag light on the right side of the dash. Car operates normally other than that.

Codes present now are:
SRS-E001: Control module communication. Faulty communication
CEM-1A64: Communication with differential electric module. Signal missing
CEM-9C03: Antenna / light ring. Signal missing
CEM-1A54: Communication with power seat module. Signal missing
CEM-1A51: Communication with the supplemental restraint system module. Signal missing

My next plan is to run through the Xemodex flow chart for the DEM and see where that leaves me. Since I don't have AWD anyway can I just run with the DEM unplugged?

Post by **vtl** » 28 Feb 2022, 16:40

cbova wrote: ↑28 Feb 2022, 16:32 Since I don't have AWD anyway can I just run with the DEM unplugged?

Yes

cbova · Post by **cbova** » 28 Feb 2022, 17:13

thank you, vtl.

cbova · Post by **cbova** » 01 Mar 2022, 10:10

Interesting series of events last night. I ran through the Xemodex flow chart for the DEM. I have battery voltage at Fuse 23 on the REM, and the fuse is good. I DO NOT have battery voltage at the DEM connector though, I have 2.x V. According the the flow chart I have a bad wire from the REM to the DEM connector. While I was down there I applied 12V directly to the Haldex motor and it doesn't run, sort of expected that. Feeling fairly confident I found the issue with the DEM wiring I unplugged the DEM connector and the Haldex connector and was going to run it unplugged for a while. I proceeded to lower the car and clear the SRS code (key had been on for ~30 while I was under the car playing with the DEM wirinhg). Plugged the code scanner in and it could not see the SRS module then I lost all dash function, no back light, no gauges, no warnings (except CEL stayed on for a few seconds and turned off). Headlights, radio, blower all worked. Car started and ran. This was different than my original dash failure though since I lost fuel gauge and back lights too. Keyed on and off a few time still no dash. Called it a night. This morning key on and dash is back. Where do I go from here? I was going to plug the DEM back in and see if the SRS communication came back but besides that I fell like I'm chasing my tail.

Now I'm wondering if it's the SRS mod bringing down the network in addition to a seemingly bad DEM wire?