ECM-644A VVT Stuff...

[carboncow]

Helping my buddy and he's got a 99-00 XC70. He was getting a p-code that lead him to believe it was the VVT solenoid so he replaced it with a brand new unit. Car has about 210K on it. A few weeks or months after replacing the VVT solenoid he started to get a CEL again. The code is the common ECM-644A.

He has since then replaced the timing belt but claims the code was showing up prior to the new belt so we'd like to rule that it's off out of the discussion.

I noted in the Vida Dice info it stated a cam position sensor is a possible source for the fault.

What is the "reset valve" it mentions in the Vida Dice?

What else to consider?

We put live values on the Vida Dice and kept a eye on angles. I read in several places if the spec is more then 7 degrees it can throw a code. At idle values are 14-15 degrees. I noted when reving values are 0 or 255 so either the system goes "offline" or they are null at higher speeds.

See attached images to see if any of this info helps.

What should we try next?

5-9-2016 7-00-15 PM.png (24.9 KiB) Viewed 4666 times

[Ozark Lee]

The reset valve is the control solenoid - different names for the exact same device.

Do you know if the preload procedure was followed when the timing belt was replaced? It is a bit confusing the way it is worded in VIDA but it is imperative that it be followed or the CVVT will limit out, throw an error code, and the CVVT will be disabled. The key to understanding the procedure is to recognize that the sprocket on the CVVT camshaft operates independently from the hub itself over a range if 15 degrees or so.

The 644A code however is usually a faulty signal code and it implies that there is a connector or wiring problem to the solenoid. In most cases the harness has to be spliced when replacing the valve since the current replacement part has no connector, just a pigtail. The valve is actuated by varying the pulse width of the square waves to the valve and if you have access to an oscilloscope you can actually see the pulses.

...Lee

[carboncow]

Thanks for the details. I believe he was pretty meticulous with preloading the hub but I'll confirm. Plus the issue was present prior to the belt change.

Any chance the cam position Sensor is to blame. VISA did mention it as a posibility although I'm curious to the probability.

He states no noticeable performance concerns.

[kahl]

Thanks for your help guys....I was getting the code before the TB change. While doing the TB I installed a new solenoid hoping this was the problem. When I did the solenoid used a new gasket and cleaned the already clean ports. I will trace the solenoid wires back hoping I will find some chaff.

[abscate]

Helping my buddy and he's got a 99-00 XC70. He was getting a p-code that lead him to believe it was the VVT solenoid so he replaced it with a brand new unit. Car has about 210K on it. A few weeks or months after replacing the VVT solenoid he started to get a CEL again. The code is the common ECM-644A.

He has since then replaced the timing belt but claims the code was showing up prior to the new belt so we'd like to rule that it's off out of the discussion.

I noted in the Vida Dice info it stated a cam position sensor is a possible source for the fault.

What is the "reset valve" it mentions in the Vida Dice?

What else to consider?

We put live values on the Vida Dice and kept a eye on angles. I read in several places if the spec is more then 7 degrees it can throw a code. At idle values are 14-15 degrees. I noted when reving values are 0 or 255 so either the system goes "offline" or they are null at higher speeds.

See attached images to see if any of this info helps.

What should we try next?

5-9-2016 7-00-15 PM.png5-9-2016 6-54-35 PM.png5-9-2016 6-53-39 PM.png

Circling back on this old thread. This one is right on the edge of coding as the criteria for coding is that the average flank angle exceeds 10 degrees. If one of those adaptation changes a bit this will code.

Solution here would be either moving the sprocket one notch counter clockwise on the belt or 1/2 of the oval space on the three M4 bolts on the sprocket to get the flanks around +5 degrees.

[Maestrours]

Solution here would be either moving the sprocket one notch counter clockwise on the belt or 1/2 of the oval space on the three M4 bolts on the sprocket to get the flanks around +5 degrees.

Hi, i exhume this thread, but are you sure of the counter-clockwise way? As you said in anotjher thread:

"IF the Flank Angle is positive, the Crankshaft reaches the mark before CAM reference mark, so the cam sprocket needs to be moved clockwise to retard the CAM"

So if this got +14/15° (which is exactly my case), you should move the sprocket one teeth clockwise to be about -1/2° isn't it?

Thanks !

[wizechatmgr]

Hi, i exhume this thread, but are you sure of the counter-clockwise way? As you said in anotjher thread:

"IF the Flank Angle is positive, the Crankshaft reaches the mark before CAM reference mark, so the cam sprocket needs to be moved clockwise to retard the CAM"

So if this got +14/15° (which is exactly my case), you should move the sprocket one teeth clockwise to be about -1/2° isn't it?

Thanks !

Is it alternating between the two readings? If so, you're off just about a tooth typically. If it doesn't alternate and hangs at the reading, you're typically off about two teeth, possibly more.

If you didn't pretension the VVT hub, base timing is going to be off big time, possibly to the point you could cause damage doing these adjustments. Make absolutely sure base time is correct with the VVT pretensioned before/during belt installation. If all your other marks are correct, but you didn't pretension it, it will be off an incredible amount.

Assuming base timing is correct, and you double & triple checked it, move VVT cam one tooth in your desired direction and see what happens at idle. If it doesn't change the angle showing, you're still far off, but in the other direction. I believe @Abscate has a better thread on this where we worked it all out. Can't remember if it was on my XC or one of his R's, but it was in depth.

You can't really check the VVT for proper actuation until the alignment is correct as it should not function to avoid damaging the engine until the angles are within spec.

[wizechatmgr]

Found the post in question:

viewtopic.php?p=541507&hilit=%40abscate ... le#p541507

[Maestrours]

I'm sorry as I'm french I'm not sure I understand well everything you said, especially the two readings part?
At idle, i read 15°, and as soon as I press the throttle pedal, it goes 0°.
My base timing is correct, the crankshaft is aligned, inlet valve is aligned, and for the moment exhaust valve is aligned;
I did it reading the haynes (which is not very clear), Vida and this forum; i did non "retension" the vvt hub, except with the belt tensionner, is it what you're talking about?

How do you pretension the VVT Hub, except by doing 1/4 turn clockwise then go forward?

Can you confirm that if I read 15° in nominal flank angle, i have to move VVT hub 1 tooth clockwise?

in all cases, thanks for the answer, much appreciated.

[abscate]

Solution here would be either moving the sprocket one notch counter clockwise on the belt or 1/2 of the oval space on the three M4 bolts on the sprocket to get the flanks around +5 degrees.

Hi, i exhume this thread, but are you sure of the counter-clockwise way? As you said in anotjher thread:

"IF the Flank Angle is positive, the Crankshaft reaches the mark before CAM reference mark, so the cam sprocket needs to be moved clockwise to retard the CAM"

So if this got +14/15° (which is exactly my case), you should move the sprocket one teeth clockwise to be about -1/2° isn't it?

Thanks !

Hmm flank angle is positive so cam is behind the crank, so the cam needs to advanced. Maybe I got this wrong in that thread! Clockwise advances the cam!