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Corrupt Canbus, xemodex said good luck

Help, Advice, Owners' Discussion and DIY Tutorials on the Volvo S80 model. Sometimes called an "executive car", the S80 was and continues to be Volvo's top-of-the-line passenger car.
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SuperHerman
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Re: Corrupt Canbus, xemodex said good luck

Post by SuperHerman » Wed Nov 27, 2019 12:36 pm

As the problem persists after the crash you are right thinking it is not the alternator. Still not a difficult elimination.

CEM and ECM, although tested by Xemodex need some more looking into. Maybe focus on the harness, socket and connectors.

I had a problem with the steering wheel module where the female side of a socket had corrosion - enough to work and enough not to work.



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Re: Corrupt Canbus, xemodex said good luck

Post by RickHaleParker » Wed Nov 27, 2019 1:15 pm

imac wrote:
Wed Nov 27, 2019 12:16 pm
I've read that canbus has 120ohm resistors as end of lines. Is that integral to the ETM on the high speed side? Is it measurable with an ohm meter? Thanks all, this is frustrating and winter is coming quick
It is two 120Ω resistor at each end of the CAN bus, for a 60Ω impedance. You can measure it with a ohm meter.

Thinking the corruption might be reflection from the unterminated AUM CAN. Measure the resistance of the old radio at the CAN inputs, then place that value across the end of the AUM CAN wires, that will absorb energy instead of reflecting it back down the line.


Platform: P80 1998 C70, B5234T3, 16T, AW50-42, Bosch Motronic 4.4, Special Edition package, Plant: Uddevalla Sweden.

Platform: X40 (Nedcar) 2003 S40, B4204T3, 14T twin scroll AW55-50/51SN, Siemens EMS 2000. Plant: Born Netherlands.

Platform P2 2005 XC90 T6 Executive, B6294T, 4T65 AWD, Bosch Motronic 7.0,
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Re: Corrupt Canbus, xemodex said good luck

Post by imac » Thu Nov 28, 2019 6:31 am

The problem manifested itself before the stereo was upgraded, so I don't think that's the issue. Looking at the canbus wiring diagram I would think the UEM and the REM have the end of line resistors. I'll disconnect the battery and check resistance next



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Re: Corrupt Canbus, xemodex said good luck

Post by volvolugnut » Thu Nov 28, 2019 3:29 pm

I am not any kind of Canbus expert, but have you tried to check the connection sockets for solid grip of all pins? You can check with a spare pin pushed and pulled from the sockets. The fit should be good with some drag. You can also use any clean, solid material of the exact same thickness (measure the pins with calipers) to do this test. There are several pins thickness used in various connectors. Any loose sockets can be carefully adjusted with a very small screwdriver to carefully tighten the connection squeeze.
The idea is a loose connection will cause an occasional open circuit.

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2001 V70 T5, 1986 244DL, 1983 245DL, 1975 245DL, 1959 PV544, multiple parts cars.

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Re: Corrupt Canbus, xemodex said good luck

Post by xiami » Thu Nov 28, 2019 9:42 pm

Hi I had this problem with my 2002 Volvo S80 T6 when it was 98,000 miles. It was the ABS Brake module, located under the ABS pump. I sent it to Automotive Scientific Inc, www.autoecu.com for repair and this problem was fixed and problem has not recurred. I still have my 2002 Volvo and now it has 203,000 miles.



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Re: Corrupt Canbus, xemodex said good luck

Post by imac » Fri Nov 29, 2019 6:55 am

I have taken apart, cleaned with electrical contact cleaner and a toothbrush, then liberally applied di electric grease to every connector I could find in the can loops and at each module. There is at least one I cannot easily get to (behind the dash) and I have not checked phsyical pin fit, no. I've pulled/pushed on the bundle of wires at the ECM/TCM with no change watching the oscilloscope.

I cut the case open on the original abs module and soldered a couple spots, no change.

I replaced the ABS module with a (supposed) good one from the wrecker, no change.

I unplugged the ABS module and drove the car (the ABS light was on the dash) but eventually the network crapped out again, without the ABS even plugged in, so I do not think it is that.

Thanks for the ideas!



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Re: Corrupt Canbus, xemodex said good luck

Post by jimmy57 » Fri Nov 29, 2019 8:45 am

The splice for ABS off the underhood CAN is in the bundle in the cowl with wiper linkage. The twisted pairs of white and green wires make it fairly easy to locate and it is taped. That panel in front of windshield is the access. You can find if you look at the wiring not far from where the harness emerges from inside the car. 99 models have some history with CAN wiring at that underhood splice for ABS on high speed CAN and under carpet in driver's footwell where the harness is under carpet in a flat plastic conduit on the low speed CAN. There is no easy access high speed CAN probe point. The CEM is a good place and you obviousy have CEM bracket experience. The CAN wires are at the OBD plug but on 99-2004 these wires are gatewayed through CEM and are not live unless a signal is being sent by a scan tool on the K line wire that is shown to that plug from CEM to OBD plug. You could use VIDA and then back probe OBD plug also.



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Re: Corrupt Canbus, xemodex said good luck

Post by imac » Sat Nov 30, 2019 8:30 am

With the battery disconnected, I have 62.1 ohms resistance on the HI speed bus, tapped in between the CEM and the TCM. When I unplug the ETM it goes to 120. Similar ~60ohm on the low speed loop, measured at the AUM plug.

The splice point in the wiper loom eludes me, it must be inside the rubber boot circled in yellow?
Nov 30b.jpg
I tapped into the green/white on the HI speed and got a dirrrrty waveform, it looks gross.
CAN Hi.jpg
Can a failing module on the LO speed, say DDM, corrupt the HI speed loop? Thanks in advance for any insight!
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Re: Corrupt Canbus, xemodex said good luck

Post by jimmy57 » Sat Nov 30, 2019 10:30 am

Yes, the splice in that boot. You may have to cut it and then wrap well with tape after you've picked it up so you can circle it with tape roll.
Before you cut show a view of CAN H and CAN L high speed individually. I can't tell which one is off here. CAN H should be 2.5 to 3.7V and CAN L should be 2.5 down to 1.2V. I think that a single CAN wire losing connection will offset the centerline voltage. It has been almost 20 years since I've seen these faults and a lot of broken cars since so my recall of every possible incident cause is mildly sketchy. The problem I saw twice was the splice sleeve (butt splice connector) was crimped with too much force and cut the wire. The positioning of the wire would allow contact but it would separate randomly. The issue on high speed from your views is different than what is happening on low speed. Fix high speed then attack low speed.
If the that splice is OK then the next check would be to see which module on high speed being unplugged causes the return of both legs sharing a voltage center line. The voltage range will change when a termination resistor module is unplugged but the one causing the problem, if it is an internal module fault and a resistive short to ground, will make the square waves return to a shared centerline voltage.
Yes, but I have only seen a CEM cause it but Xemodex has checked CEM. No way there is water in wires on back of CEM?



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Re: Corrupt Canbus, xemodex said good luck

Post by imac » Tue Dec 03, 2019 7:04 am

There's no evidence of water on/in/near the cem, and everything looks good above it when viewed from the windshield wiper side of things.

To eliminate the possibility of a bad splice or broken wire I re-wired the high speed canbus from the CEM to ABS and TCM using belden "blue hose" wire, which is a durable twisted/shielded pair used for devicenet in industrial settings, it's has a thousand times better shielding than just a twisted pair. I bonded the shield to ground at one end of the cable only so any induction drains to one end and no ground-loop can be produced. I cut in about 4" away from each module, abandoning the green/white in the loom entirely.
rewire.jpg
The jumper from TCM to ECM looked fine, plus rang out fine with a meter while shaking/bending the green/white pair, they maintained continuity so I left it alone.

I used a torch tip cleaner to clean up the 6x hi speed can pin sockets at the TCM and ECM plugs, checking continuity as I went, everything is good, same for the 2x at the ABS module.
ecm tcm.jpg
abs.jpg
I have eliminated wiring as a possible cause. The joint where the 3 wires connect, (and are bonded to ground) I put my oscilloscope and volt meter on.
cem plugs.jpg
(CAN HIGH)
White to Ground = 2.3vdc
Green to Ground = 1.8vdc
White to Green = 0.5vdc

Probing CAN HIGH White to Ground:
white to ground.jpg
-
Probing CAN HIGH Green to Ground:
green to ground.jpg
-
With the ECM and ABS disconnected:
no ecm.jpg
-
With the ABS, ECM, TCM disconnected, so JUST THE CEM, White:
white from cem.jpg
Green:
green from cem.jpg
-
With nothing hooked up to the CEM on the high speed loop, I reconnect the battery and after a few seconds it goes to BRAKE FAIL on the DIM.
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