ECM 640A & ECM 641A (CVVT issues) - new parts, same problem

Bikey · Post by **Bikey** » Mon Nov 26, 2018 1:11 pm

Hello. I have been chasing a ECM 641A (Exh Cam Control - Faulty Signal) problem for a while. About a year ago I bought a Pro Parts Sweden exhaust cam solenoid (aka cam reset valve) and it did not solve the problem. Then I started to get an ECM 640A (same problem as above but on the intake side). The car seems to run fine at all times, other than the MIL light.
So, I got a Pro Parts Sweden intake cam solenoid and new OEM intake and exhaust CVVT hubs (along with new timing belt and tensioner).
I installed all of that per the CVVT guide I found on this site.
The car runs exactly the same as it did before.
From looking at the VIDA inlet and exhaust cam parameters, the obvious problem is that nominal and actual exhaust cam shifting angles are way off (actual shifting in the ~2CA range, nominal at 25CA). It appears that the exhaust CVVT setup is not working though with that kind of error, it would seem like the exhaust hub was not in its forward-most position, so I will double check the positioning of the exhaust hub.

: Cam Shifting Values - Readout; vida - cvvt - large 2.jpg (52.63 KiB) Viewed 1162 times

I've also attached some graphs that show the intake and exhaust nominal vs actual values over time and the inlet and exhaust adaptions, in each case with some healthy throttle stabs. As you can see on the graphs, the exhaust hub kind of lazily and randomly shifts around and the intake hub basically ignores the commanded increases on the throttle stabs. None of that seems too encouraging.

: Inlet variation

: exhaust variation

: adaptions

The car is an '05 2.4 N/A with ~50k miles. The car did not get used much before I bought it and does not get used much now. I changed the oil when I got it at 48k miles and again (one year later) changed it at 51k, along with using LubriMoly engine flush. There appeared to be some sludge on the filter. I put in high quality synthetic each time (Valvoline and Pennzoil).

Any suggestions on what to do next, other than confirm exhaust hub install?

Bikey · Post by **Bikey** » Tue Nov 27, 2018 10:41 am

I know you were dying to help and were silently saying "if he only posted some graphs of the cam shift angles while driving after resetting the CEL but before the ECM fails the CVVT system". Well, you are in luck.
It looks like the intake and exhaust sides work to some degree, with intake working better than exhaust, but both cannot get close to what the ECM is commanding. I don't have any prior experience with this system but my SWAG is that that there is weak oil flow to the cam control solenoid and/or the CVVT unit. I'm not sure if this is the result of the Pro Parts Sweden cam control solenoids or if there could be some other reason (like a blockage of some sort - would love to hear how to diagnose and fix that, if it is a real possibility).
One question I have is: what problems can be ruled out given that the adaption angles on both the intake and exhaust are within spec?

Intake Cam

: Intake cam shift graph

Exhaust Cam

: exhaust cam shift graph

Post by **abscate** » Tue Nov 27, 2018 8:15 pm

It's Volvo OEM all the way for those kHz modulated solenoids, cheap parts won't do.

On a budget, go to a junkyard and get used from a June rollover, they don't fail often

Bikey · Post by **Bikey** » Tue Nov 27, 2018 8:24 pm

Thanks, I ordered some OEM ones as swapping them is the easiest next step, we'll see how they work out.

Bikey · Post by **Bikey** » Tue Dec 04, 2018 10:44 am

The thrilling conclusion to this is that used, cleaned OEM intake and exhaust cam solenoids worked perfectly and after a bit of driving, the CEL is gone. I replaced them one solenoid at a time due to one getting delayed. I put on the replacement exhaust solenoid first and it worked way way better than the Pro Parts Sweden unit but the exhaust solenoid didn't start working perfectly (i.e., no pending or thrown codes) until I replaced the Pro Parts Sweden intake solenoid. Once both were replaced, it took a little while (idled for 5min) and then they both worked properly.

Here are some graphs of the properly functioning CVVT systems.

: driving on slower local roads

: accelerating onto highway

EngineeringBloke · Post by **EngineeringBloke** » Tue Dec 04, 2018 4:49 pm

Thanks for the graphs, they are informative. And I am glad your issue is resolved. I really must get Vida.

I had a slow exhaust CVVT code that went away after I cleaned the solenoid and replaced the solenoid gasket, although I did not see any clogging of the oil passages. Code has not returned.

Post by **abscate** » Tue Dec 04, 2018 6:23 pm

The follow up and resolution is appreciated and makes MVS better

DanelleNavarro · Post by **DanelleNavarro** » Thu Dec 10, 2020 9:52 pm

My 02 v70 xc is giving me 641A code for my exhaust camshaft control. I have no idea how to begin to fix this issue. Any help will be greatly appreciated!!

Post by **abscate** » Fri Dec 11, 2020 3:51 am

If you have been keeping up with oil changes then usually cleaning or replacing the solenoid will fix this. If you had the timing belt done recently, they mucked it up.

The solenoids aren’t cheap so junkyard ones are easier in the wallet

jonesg · Post by **jonesg** » Fri Dec 11, 2020 6:38 am

DanelleNavarro wrote: ↑Thu Dec 10, 2020 9:52 pm My 02 v70 xc is giving me 641A code for my exhaust camshaft control. I have no idea how to begin to fix this issue. Any help will be greatly appreciated!!

they need good oil pressure to work properly, old dirty oil messes them up.

You can clean and test the solenoid on the table , get a couple of gaskets first.