throwing in the towel perhaps

warcraftjunkie · Post by **warcraftjunkie** » 09 Nov 2012, 18:46

Here's the notes from the tech.

"Vehicle would barely run. Kept stalling. Inspection found disconnected MAF sensor. Aftermarket throttle uniet (ets light illuminated). VIDA was unable to read vehicle powertrain BUS modules even when VIN was manually input. VOM tests showed proper voltage and ground at datalink connector. Disconnecting modules one at time still did not restore BUS readability even after battery reset. Tests indicated CDM failure (Part of instrument cluster circuitry). Causing loss of communication through vehicle. Also found MAF sensor shorting out 5 Volt Sensor feed. Estimate given for replacement of CDM, MAF sensor, and aftermarket ETM - Repairs Declined. Note: ABS module is disconnected. Connector slide mechanism was previously broken."

Bascially he said that the CDM is dead and that the TCM and ECM are having a hard time communicating with each other because they are downstream of the CDM and communicate with each other through it. Being a network engineer I understand this concept and it basically is acting like a hub where all data communications are sent through.

Post by **jblackburn** » 09 Nov 2012, 19:14

Oh wow. Networks in cars...what a terrible idea.

Post by **northernlights** » 10 Nov 2012, 05:42

Well...I am not a network engineer, but I am going to have to call shenanigans on the explanation. Here's a few attachments which may prove helpful. Note on page 90 and 91 that the TCM and ECM communicate directly through CAN without involving the CDM. Also note that the CDM communicates with what appears to be the diagnostic port through CAN, and that only three wires appear to go from the ECM to the CDM.

These came from a file on this site. Unfortunately whomever scanned it in mixed up the page order and lost a couple pages - that's why the component list in incomplete.

I think these guys don't understand the electronics. Quite a bit of the hardware does communicate through CAN, but definitely not all of it, and certainly not all of it through the CDM. If everything was networked together, then why are there so many wires running from component to component?

-Eric

warcraftjunkie · Post by **warcraftjunkie** » 10 Nov 2012, 09:37

Thanks for pulling those. I downloaded the schematics and absolutely you are right. I guess I was just hoping beyond hope that it would be one simple point to fix.

Post by **northernlights** » 10 Nov 2012, 10:42

My pleasure. I have a pet peeve about dealerships charging good money for questionable diagnoses.

-Eric

Post by **osman** » 10 Nov 2012, 12:23

We all do, Mr. Aurora Borealis.
ETM's and MAF's run in sync in the way that the data they collect (air flow speed/density and throttle position) received by the ECM for ail/fuel ratio considerations along with the O2 sensor they tend to fail together, or one failing tends to take the other with it. Better to replace at the same time.

warcraftjunkie · Post by **warcraftjunkie** » 10 Nov 2012, 23:51

Well, I'll have to dig in again after the snow melts. We got over a foot of snow here today with forecasts for it to continue tomorrow. I was going to haul it into my garage and start picking through the electrical again... as well as remove the dash and look in there for any suspects. Don't want all that snow melting off the car in the garage.

warcraftjunkie · Post by **warcraftjunkie** » 16 Nov 2012, 08:13

Ok, I'm spending this weekend going through the electrical connections with a fine tooth comb. I checked all the engine bay ground points and tested them. All are solid. I did another voltage drop test on the B+ cable to fuse box, it's good. I'll be doing a test of the Engine mgmt relay and "Air pump" relay later to make sure they are still good.

I've pulled out the instrument cluster to take it apart as the Volvo tech said my problem is the "CDM" inside of it. I'll be looking for obvious signs of swollen capacitors, cracked solder joints, etc.

I have a couple questions about a few things in the vehicle that I could use some identification help with. 3 pictures for your review. I'm just more curios about what these things are than concerned about them.

This appears to be some type of electrical motor or sensor. plugged in on the exhaust side of the engine underneath the spark plug cover.

And finally, what is this module on top of the instrument cluster?

What are these 2 screw holes for? They are outside of the spark plug cover on the rear of the engine near the turbo pipe.

Post by **northernlights** » 16 Nov 2012, 16:56

This first one looks like a cam phaser for the VVT, which I assume this year has. Exhaust only perhaps?

Is the connector on the top of the cluster 3 or 4 pins? I bet that it is shown on the electrical diagrams, and knowing the number of pins would make IDing it easier.

I don't know what the top holes are for. My 94 doesn't have them, and my head casting does not have blank bosses in place.

-Eric

warcraftjunkie · Post by **warcraftjunkie** » 16 Nov 2012, 17:16

The connector on top of the custer has 4 pins, I should have taken some additional pictures of it from other angles. It simply mounts to the top of the instrument cluster, but doesn't have any direct connections to the cluster.

throwing in the towel perhaps

Re: throwing in the towel perhaps