VVT issues, XC90 with a 2.5T, ECM-640A and 641A [ failed wiring] Topic is solved

Khorn09 · Post by **Khorn09** » 22 Jul 2019, 15:47

Hey guys!

So guys I got an XC90 with a 2.5T engine. some months ago. I posted on here a few different times and you guys have been pretty helpful. However I did figure out most of my problems on my own, I can't seem to figure this one out. So I'm coming to you guys and hopefully you can help me out, if not well at least thanks for trying.

Tell the problem right now that I'm having is I just had a check engine light come on. So I plugged in my Vida and it came back with both ecm-640a and 641a. After a search I found that it's related to the variable valve timing not being fast enough. Or something along those lines. So I checked the timing for the cams in the software. The intake seems to be fine, it follows the what the computer wants within about .03-1.5° at all times. The exhaust however starts out fine, within the same spec, but as the engine gets hot it gets really erratic. Like bouncing back and forth and doesn't stay steady anywhere. Like the engine wants 19° but it's at -5°??

I changed the exhaust vvt solenoid with a junkyard one, and it acted the same way. Initially fine, then all over the place. The truck seems to run fine. Also when I was revving to check the intake side cam timing it went as high as 50° when revved steady at 2500. That's what the computer wanted?? I don't know enough about this to be scared or not.

Khorn09 · Post by **Khorn09** » 23 Jul 2019, 15:27

Just an update guys, As of right now i think i figured out what it was. No CEL right now. and after a long time of running the vida cam timing app and verifying it. both cams stay within 0-1.2 degree variation now.

I opened up the cam covers, and verified the timing marks were still good; and they were. Checked TB tensioner; still looked good. check the cam sensors; swapped them, and they acted the same way. Tried unplugging the vvt solenoids while the truck was running and got no significant change. However, what I did find was the plastic tubing that covers the solenoid and coil wires was melted through. An exhaust solenoid wire had rubbed/melted through as well and was grounding out. So i just taped it back up, and am getting ready to grab some convoluted tubing to replace. Anyways, that seems to have done it. :shrug: hope this helps someone else! If I report back on this post, then you'll know that wasn't it!

Chili58 · Post by **Chili58** » 15 Jan 2026, 08:59

Was it that the reason, or is it another reason?

Post by **jonesg** » 16 Jan 2026, 05:02

Chili58 wrote: ↑15 Jan 2026, 08:59 Was it that the reason, or is it another reason?

it can be the wrong oil or dirty oil.

Chili58 · Post by **Chili58** » 16 Jan 2026, 05:28

Yes, I kniw that; but not in my case.

Post by **DavidE7** » 16 Jan 2026, 06:53

If you are replacing the VVT convoluted tubing, pick up the other sizes that fit the spark plug coil wiring. You will save yourself from the same problem with broken wire insulation and grounded signals for the coils like you did for the VVT solenoids. Buy HDPE or PE (high density polyethylene) or PA (nylon) material convoluted tubing instead of PP material. PP has poor durability. Covering all the underhood wiring with convoluted tubing and high temperature electrical tape also reduces the risk of rodents chewing on the wire insulation.