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Discussion Starter · #1 · (Edited)
This morning, I tried to start the car and it wouldn't turn over. DIM message of Immobilizer and Brake Failure, Stop Safely. I tried pulling fuses, disconnecting battery for a few minutes. No luck, so I gave up and went back inside. I had my wife drop off my VIDA laptop and a few tools and when I went to leave at 3:30, same issue. I tried disconnecting battery again, nothing. When I scanned it, there were 5 CEM codes all relating to communications with other modules. After messing around for 30 minutes, I was one or two more attempts away from calling AAA for a tow home, and then it started...but I had anti-skid message, transmission service message, brake message. It limped home in 3rd gear (at least the A/C was working well). I scanned it when I got home with it still running and you can see all the codes that were up. I erased the codes, shut off the car, and it started back up normally. No issue, and no codes other than unimportant 1 or 2 that have always been there.
Is this a sign of a failing CEM or is something else going on?

Also, while driving home, my cig. lighter USB charger / voltage display was showing 12.9-13.0 volts, so clearly the charging circuit was running right. After clearing codes & restarting, it was back up to 14.1.
 

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I believe you had a HS-CAN disruption of some length, it prompted me to look a little more deeply in VIDA and there's a reasonable amount of information about vehicle communications, including a special section on CAN itself- "Fault tracing/General Diagnostics and Test/372/General Information about fault tracing in the CAN network".

The CEM codes (Information about the CAN network, structure and function section) suggest that you had a loss of heartbeat for most of the modules, there's a comment about this NOT being the CEM most times. You might check history and see if any of these have been around before and if one module has complained more than the others.

My guess is a very good inspection of all the grounds and connectors on the modules under the hood might be warranted as a first step. Battery is not original, right? Gotta ask, given the MY.
 

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Discussion Starter · #3 ·
I'll have to dig up a diagram of all the grounds. I know there are many. Battery is ~1 year old.

On another test drive last evening, everything seemed OK except I noticed the voltage was 14.1 at startup and then after I started driving, it would stay right on 13.5. I need to double-check the plug on the alternator to make sure it hasn't backed out or anything. Is it the CEM or the ECM that regulates the alternator's output?
 

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ECM for V8 and I6.

For V8, EWD notes the alternator LIN line B:1 as a solid Green conductor to ECM A:25 (versus the more customary Green/White).

Thanks for the confirmation on the battery.
 

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Discussion Starter · #5 ·
ECM for V8 and I6.

For V8, EWD notes the alternator LIN line B:1 as a solid Green conductor to ECM A:25 (versus the more customary Green/White).

Thanks for the confirmation on the battery.
I remember seeing that wire when I did the alternator last year. It was a thicker wire, too, IIRC.
I wonder why I'm seeing different voltages now. Today it hung at 13.8 on all my drives.
 

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Discussion Starter · #6 ·
I suppose it was the hot temps that had my thinking the voltage was lower than normal. I ran through the VIDA alternator test and the voltage responded appropriately with the simulated temperatures.
 

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Discussion Starter · #7 ·
Same issued occurred last evening, although in a different manner. Just having driven through torrential rains for 5-10 minutes, the Anti-Skid message appeared, followed by a brake failure message a few seconds later, then transmission service required. It was stuck in 4th gear for the remainder of the drive home. I managed to get connected with VIDA / DiCE this morning, but then the symbol showed "Disconnected" and I was unable to re-establish connection and clear codes. There was a code that caught my eye regarding CAN-H signal on the CANBUS. I am going to pull things apart shortly and inspect pins, but I have a feeling this will be making a trip to XeMODeX this week. Can't be driving around on eggshells.
 

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Discussion Starter · #8 ·
After clearing codes and starting the engine (yes, amazingly it started), this is what occurred. Same behavior as I encountered while driving last evening.
I'm already in touch with XeMODeX to see about CEM repair candidacy.

 

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Rain, huh ? https://forums.swedespeed.com/showt...from-water-intrusion-Do-I-have-the-new-design , NHTSA link does not work but it's applicable with the XC90 from chassis 134000 to chassis 256551 (applicable to the entire P2 line, individual chassis range per model)). I might have a copy of the TJ in my share in the How-To sticky- "XC90_CEM_PlenumLeak". I did the revised cover (flat now, not raised as before) on my '05 a year or so ago, not sure if it's worth the hassle since some of the wiring goes back on the driver side doorsill and the connector barely gets over the silicone rubber boot. HongKong just pulls the cover and runs a bead of silicone on the base before putting it back on. Viable option in my opinion, just for peace of mind. Not an issue that's seen a lot but it is a known issue...
 

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Discussion Starter · #10 ·
Rain, huh ? https://forums.swedespeed.com/showt...from-water-intrusion-Do-I-have-the-new-design , NHTSA link does not work but it's applicable with the XC90 from chassis 134000 to chassis 256551 (applicable to the entire P2 line, individual chassis range per model)). I might have a copy of the TJ in my share in the How-To sticky- "XC90_CEM_PlenumLeak". I did the revised cover (flat now, not raised as before) on my '05 a year or so ago, not sure if it's worth the hassle since some of the wiring goes back on the driver side doorsill and the connector barely gets over the silicone rubber boot. HongKong just pulls the cover and runs a bead of silicone on the base before putting it back on. Viable option in my opinion, just for peace of mind. Not an issue that's seen a lot but it is a known issue...
I was curious enough, so I pulled the CEM (most likely going to XeMODeX, anyway), and took it one step further to remove the CEM board(s) from the housing. It looks great. I don't see any evidence of corrosion on any of the terminals or components. I'm leaning toward the failure being related to heat, which is one of the common reasons. This coincides with the first time I experienced these issues. It was extremely hot outside and the car was parked with the windows up.
Also, I don't see any evidence of water intrusion around the CEM's upper cover, although there is a tray of wires that lay underneath the mesh shroud under the windshield wipers, and the wires are not protected by a cover. There is some debris in there, so I find that shroud is a poor design.
 

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Discussion Starter · #11 · (Edited)
Occurred again last night. It was on a cold start, so definitely not heat related. No rain, either. XeMODeX mentioned that maybe the DEM was causing high-speed CAN issues, and said to disconnect it as a test. I crawled under the car and disconnected the DEM's main connector. Car still wouldn't start. We had to grab an Uber, get my wifes car, and come back to it. By that time, the car at least started, but the issue occurred while driving and went into limp mode for the remainder of the drive home. I'm desperately trying to isolate this issue now. I thought maybe I could disconnect all the modules that talk on the high-speed CAN (that aren't required for starting), one-by-one. It looks like BCM, TCM, SUM, and DEM. Is the DIM on the high-speed network on the 2005 models?

Thinking about this further, if the DEM crashed the high speed CAN, and I disconnected it, should I expect the car to start behaving OK right away after a quick key cycle (off-on) or would I need to let all the modules "sleep" first or give it a proper several-minute power cycle? In other words, could the DEM have crashed it, and even though it was disconnected, all the high speed modules never slept so when I tried to start it again, it didn't matter?

This scan was from this morning. And then after running for a few minutes, I have two codes (will post shortly) regarding the alternator. And the voltage output is 11.5v while running. This is a brand new symptom.
 

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Discussion Starter · #12 ·
After a few more attempts, I could not get the voltage to charge, and I measured 11.3 volts right off the alternator while it was running. Seems like its shot, so I pulled it out. Signs of oil around the connector and the module. From what I've read, the valve cover gaskets go bad and can leak oil directly onto the alternator. Not sure if this is the culprit or just a coincidental failure. (Lucky for FCP warranty)
Since the failures would sometimes occur right at trying to start the car after a normal shut-off, I doubt this to be the issue, but maybe someone can convince me otherwise.
 

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I forgot something else about the rain thing, your 3-way washer valve is complete and tight under the hood (passenger side) ? It's another well known failure area due to heat. If it leaks badly, it also leaks onto the alternator.

I was also wanting to lean in the direction of alternator as a possible suspect at this point, in part based on your MY and dougy's recent resolution of his long standing problem.
 

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Discussion Starter · #14 ·
I forgot something else about the rain thing, your 3-way washer valve is complete and tight under the hood (passenger side) ? It's another well known failure area due to heat. If it leaks badly, it also leaks onto the alternator.

I was also wanting to lean in the direction of alternator as a possible suspect at this point, in part based on your MY and dougy's recent resolution of his long standing problem.
I'll check the 3-way valve. I have noticed that if I don't use it for a few days, it takes a couple seconds to pressurize the driver-side nozzle.
Got a link for dougy's resolution? I haven't come across that thread but could use some reading.
 

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https://forums.swedespeed.com/showthread.php?582567-2008-XC90-V8-misfire-question was what dougy posted that appears resolved by an alternator replacement, completely forgot to mention the washer valve- https://forums.swedespeed.com/showthread.php?348097-washer-fluid-line-broken

PSA:
For any V8 owners reading, it's that time of year to give the 3-way cap a little wiggle, best it come off now than later. PNs in the second link.
For everyone, pop the hood and check your drains above and below the cover mesh at sides of the windshield base cover and make sure they're clear. Other side of the drain is a flap valve (can see from under the vehicle), can get clogged as well.
 

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Discussion Starter · #16 ·
https://forums.swedespeed.com/showthread.php?582567-2008-XC90-V8-misfire-question was what dougy posted that appears resolved by an alternator replacement, completely forgot to mention the washer valve- https://forums.swedespeed.com/showthread.php?348097-washer-fluid-line-broken

PSA:
For any V8 owners reading, it's that time of year to give the 3-way cap a little wiggle, best it come off now than later. PNs in the second link.
For everyone, pop the hood and check your drains above and below the cover mesh at sides of the windshield base cover and make sure they're clear. Other side of the drain is a flap valve (can see from under the vehicle), can get clogged as well.
Washer Tee looks good. No issues there.
 

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All good, and I got my yearly warning out. Thanks !
 

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Discussion Starter · #18 ·
So it is possible for a failing alternator to cause all these issues, even prior to the car being started?
 

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So ACM is LIN and the codes are primarily CAN, you're right in that they're separate systems.

I still think something is causing havoc on the majority of the modules. You checked grounds, you've had a few modules off and they're not corroded, you've disconnected a couple(?), and have come across an oily alternator (rear bank VCG leak) . I'll guess at this point you're going to change the alternator out, maybe see what comes back after that.

Odd problem for sure.
 

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Discussion Starter · #20 ·
I haven't disconnected the TCM nor BCM (yet) to see if the problem occurs. Can the car run without the BCM? Will the car run without the TCM? (limp mode?)
Yes, I am swapping the alternator because it appears dead at this point. Also going to do the VCGs to prevent this from reoccurring.

I'm trying to think ahead and prepare because I can't imagine this is going to be resolved, although if it is, great. Assuming FCP can overnight the new one, I'll have it installed by Tuesday evening.
 
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