2004 XC90 2.4 FWD, OBD to USB cable for CAN monitoring

[Imllay]

Any opinions about OBD to USB cables to connect to a laptop for monitoring the CAN signal, using for instance Kvaser CAN king?
I have a vexing No COM problem involving the BCM and CEM. I can communicate and use activations on both modules using VIDA.
Checked all fuses. All 3 boxes.
Removed the BCM - no corrosion, has both powers and grounds at the connector.
In process of removing the CEM to check for corrosion - who thought putting it in the cowl drain area was a good idea?
Checked the OBD connector pins 6 and 14 for ohms - nothing.
Unplugged the green plug on the Infotainment center, jumpered the CAN wires (to eliminate the connector) and get a jumpy reading of about 59 Ohms. By jumpy I mean it is not steady jumps a bit higher then lower.
My 2010 V50 gives a steady 59 ohms at the OBD connector.
No anti skip message displayed.

[yagger]

You can't get 60 ohms from OBD connector on 1999-2004 MY cars. There are separated CAN bus segments for that cars. When you connect DiCE and start to read car, same time DiCE send special commands to CEM for turn on relay and connect OBD CAN bus segments to car CAN bus segments. Only after that DiCE can read all modules.

[Imllay]

Yagger,
thank you for the reply. At least I know there is nothing wrong with my OBD connector.
So there must be a hack to tap into the CAN line and view the wave forms. Is it as simple as tapping into the line like I have done at the Infotainment connector, using a USB cable? If so, which wires in the USB cable should I use?

[ggleavitt]

Links on CAN for those curious, one or two include LIN-
https://en.wikipedia.org/wiki/CAN_bus
https://people.kth.se/~kallej/papers/ca ... book05.pdf
http://esd.cs.ucr.edu/webres/can20.pdf
https://obdclearinghouse.com/Files/viewFile?fileID=1280
http://www.ti.com/lit/an/sloa101b/sloa101b.pdf
https://arxiv.org/ftp/arxiv/papers/1802/1802.01725.pdf
https://www.csselectronics.com/screen/p ... anguage/en
https://training.ti.com/automotive-can-overview
http://socialledge.com/sjsu/images/d/d0 ... mer_v2.pdf
https://www.eecs.umich.edu/courses/eecs ... _notes.pdf
https://copperhilltech.com/a-brief-intr ... a-network/
http://www.libelium.com/downloads/docum ... _guide.pdf

[Imllay]

ggleavitt - thanks for the links, I have read them.
Still no information on actually connecting laptop to the CAN on a 1999-2004 P2 volvo.
I have one of those cheap ELM readers that will connect and read off codes, coolant temperature, fuel trim, etc using the Torque Android app.
This reader must be telling the CEM to activate the relay that connects OBD to the CAN bus - per yagger above.
Has anyone used one of the available ELM cables that connect OBD to USB?
Have you successfully used it on a 1999-2004 model P2?
If so, which one do you have?

[yagger]

You should to connect to active High speed CAN segment. If you have a "good hands" you can connect directly to wires.
You can find it clothe to CEM connector (B:17 and B:18 contacts).
Look attached image.

[Imllay]

Thank you Yagger. I am going to drop the CEM down from the bracket under the dash to check for water damage. I will check the CAN resistance also.

[ggleavitt]

Sorry, I should have read your first post more clearly.

For chassis range 134000-256551 (last 6 of VIN), the cover over the cowl had a process identified for replacement due to water ingress. Includes troubleshooting flows plus some sunroof stuff, came from public site (safecar.gov) a while ago-

XC90 Water Ingress.pdf

(2.87 MiB) Downloaded 1818 times

I replaced the cover in my '05 (chassis 135488) last summer but only because the kit had been sitting on a shelf in the garage for quite a few years and I felt guilty. In retrospect, it was a PITA to do and I would have spent my time more wisely in simply lifting the lower cover and squirting some clear silicone underneath before tightening the 4 screws back down.

Still does not answer your initial question fully but thought the attachment might be worth posting.

Good luck with your repair.