'04 XC Engine Misfiring-Further Updated (Moisture ruled out - possible defective coils, bad MAF) Topic is solved

[chrism]

Perhaps ECM jolted loose by bouncing up and down the driveway?

When I mentioned re-seating the ECM earlier in the thread I was thinking more about dirt and oxidation on the 16 year old connections rather than the unit shaking loose. (But hey, you may be right.) When you get numerous, and seemingly unrelated, fault codes one of the places that comes to mind as a “common point of failure” is the ECM connection. Tons of data has to flow through that connection and when it’s interrupted all the system knows is that the signal from “air sensor X” or “throttle sensor Y” is out of range so people tend to jump at the opportunity to start replacing parts.
Make sure the mechanic cleans that connection and firmly re-seats the ECM before they too want to start playing musical parts. I could be all wrong but it wastes all of about one minute to try it.
Good luck!

[- Pete -]

I have a roller coaster/mogul field of a steep gravel driveway. Perhaps ECM jolted loose by bouncing up and down the driveway?

Regardless, it is going to my local indie. I need the car, and fiscal year end demands at work will preclude me from getting to it.

Evan, if you need an ECM removal tool they are like $20 on eBay/amazon. At least you could check for corrosion etc if you had one.


I’m having some similar suspicions with our 04XC70 in respect to the ECM being possibly flakey. In my case I can’t get the car to reproduce the symptom(s) when I have ViDA hooked up. Also, the codes that do repeatedly get produced are spurious and/or completely unrelated. However, if I clear these in ViDA the car runs better/stronger. I don’t have any misfires nor sensations of a bad coil, though. What I do have is an intermittent loss of boost the source of which feels very electronic in nature. Seems to present itself more frequently on hot days, but inconsistently so. With ViDA hooked up I can’t get it to reoccur at all. What seems to trigger it is if I’m not watching my boost gauge & let it climb over 15psi it feels like it enters a limp mode. Afterwards it seems limited to 7ish psi, however this can be inconsistent as well seeing as I can coax it up to 9-10ish psi. Almost all of the bits on my pressurized side are new, including both turbo hoses, MAP, TCV, ETA (formerly referred to as ETM 01-02), vacuum lines all check out, MAF cleaned, verified Wastegate set appropriately (4ish psi), and all of those efforts made almost no difference whatsoever. The only code I ever had was an ECM 392 - faulty communication I believe it was. I didn’t check how many days it had been populated for so it could easily have been from long ago, and since that initial clearing of it it has not repopulated. Anyhow, sorry to not be of any help, but I’m working on something that seems equally as evasive as with your 04.

Is your ECU fan operational?

I may have stumbled upon an obvious solution with our 04 XC70. I just ran the car for a short 400ish mile trip yesterday with ambient temps hovering around 90* F and didn’t have a single episode. Prior to this I would safely say it was occurring about 1/3 of the time. The fix was to remove both the ECM/TCM, clean the contacts with contact cleaner, I then used spray dielectric grease and plugged both modules back in. I did use my tool to work the modules up and down so the pins would sort of “clean” the petals. Anyhow, hopefully your indie fix will be similar and inexpensive. I know I’m happy again with mine! Pissed I spent $500 or so in parts to realize I had the fix in the garage the entire time but oh well.

[3carmark]

I'm an ase certified master tech and you need to look at multiple things on Vida to locate your problem

[chrism]

Pete says “... Pissed I spent $500 or so in parts...”

You’re not alone. I spent $350 on a brand new Bosch throttle body because of all the throttle position etc fault codes that I was getting due to a faulty ECM connection. That’s why I continually harp about checking that connection early in the trouble shooting process especially when you’re getting multiple unrelated codes. I’m sure the other folks here are tired of hearing it from me. But it is such a quick and simple thing to check and it costs so little to do that. I just wish there was a fault code that read P6969 “Hey dummy, check the ECM connection!”

[- Pete -]

Yes, you are absolutely correct. Reading back through this thread I can now see that I missed your harping on this point. Such an easy thing to overlook but it is the at pinnacle of a heap of parts that can act up if it itself isn’t able to read the various communications correctly! This entire time I had the ECM in the back of my head as a possible culprit but it was on the bottom of the totem pole of other possibilities. I too replaced the Bosch ETA to the tune of $350 some dollars & it accomplished nothing. I spent many hours with ViDA over the last several months with this car, charting parameters etc and nothing made sense & no relevant codes to clue me in.

Anyhow, Chrism, please continue to harp on this point and I too will be doing the same! What’s amazing to me is the pins all looked pristine on my modules. I’m guessing the petals below are the culprits.

Edit: I truly believe every P2 owner should invest in the $20 ECM/TCM removal tool. I also strongly feel that performing this simple task of removing, cleaning the contacts & applying some (spray) dielectric grease should be standard procedure in stage zero-ing any car.

[E Showell]

No definitive diagnosis yet. Independent suspects "rodent damage to wiring." Should know more soon. Will report back.

[E Showell]

Indy has thrown in the towel on it. Taking it to a very well-regarded independent Volvo specialist on Tuesday. Probably report back end of next week.

I have been using this local independent for 15 years. This is the first time he had told me he can't figure out the source of a problem.

[abscate]

Did anyone try a new set of plugs? I know they have 5k on them but they can OBQ AS well as delayed OBQ FAIL.

OBQ out of box quality failure

[- Pete -]

Did he pull the ECM/TCM out for cleaning & spray lubing the contacts?

[E Showell]

Far as I know, no to both of above questions. Volvo specialist thinks it may be a fault with the wiring harness that goes to the throttle body. He said he has seen them fail.