2.0 VAG Variable Valve Timing Testing with a Scope
Here is a link that my fellow Tech and I would like to share. This test was done on a perfectly working 2008 GTI (mine)
Awesome stuff and a huge shout out to Chris Martino for his never ending efforts to find fixes and roll up his sleeves.
Within that page you'll find an embedded YouTube video and I figured that I would link it here as well.
Thank you for the excellent video! I'm going to try that one.
Ray
Great video You can also use in cylinder pressure transducer and watch the change dynamically. It will take a little longer but would be nice to see.
Im missing something. Say p0012. Which I assume could come up if nothing happened when commanded by pcm. Would the leads need to be moved in order to tel if it were the solenoid or phaser that has failed? I can't see how we would know which component failed using that data. I get ohming solenoids and other diagnostic ways. But pertaining to scope work. Thanks guys
I find that this is a good way to determine if the VCT actuator's pintle is either stuck partially open or if the solenoid's pintle isn't moving at all.
The red CH B is the VCT actuator's control wire, which is PWM by the PCM, until I grounded the control wire.
The green CH C shows the solenoid's pintle being pulled off of it's seat at 815ma,
With the actuator's pintle open, the oil pressure could then flow to the phaser, which would then retard or advance the cam timing.
Ray
OK. Did you use a scanner, power probe or test light to ground the control? Also, did you use a low amp probe around the control wire at the same time to take these measurements? Both channels were on the same wire at the same time?
I tapped the control wire to ground with a ground wire. The power to the actuator was fed from a fuse on the 2014 Hyundai Elantra and the engine was at idle, so the PCM was not normally trying to open the VCT actuator. The actuator's pintle was closed at idle before I opened it.
The amp probe can be on the power wire or on the jumper wire, to see the solenoid's pintle being pulled from it's seat, when you tap the control side of the solenoid to ground.
The red CH B was on the control wire to the PCM.
On most engines, I think that the rpms should be held off idle, so that the oil pump can produce the oil pressure necessary to turn the phaser to it's maximum.
A scanner should be used to monitor the ignition timing advance because on some engines, the PCM advances and retards the ignition timing at idle to stabilize the idle without moving the throttle plate.
So when using the COP trigger with the cmp, the rpms should be held off idle to stabilize the ignition timing advance.
Ray
I just did a timing chain on one of these last week and I happened to use your tech tip from iatn, Ray. Good stuff. I'll add this one to the arsenal.
Tthanks for the help Ray. I'm waiting for an opportunity to try this out. When I do I'm sure I'll have more questions lol
Ray I gave it a shot. On the green trace I believe the first hump is the pintle lifting off just over 2 millamps. Very cool stuff. Thanks so much I like this testing method much more. My yellow trace was on power feed. I later moved it to control wire but was unable to find a duty cycle or pwm. This was on an older bmw and I believe it was a straight forward on/off command from pcm. This is a known good vehicle.
Hi Chad, the wave form looks excellent!
The pintle hump can't be 2 milliamps, it must be 200 milliamps and the total amp draw looks like 400 milliamps, which is under half of 1 amp.
Did you measure the resistance of the solenoid?
You right, some engines don't use pulse width modulation.
If you have a 4 channel scope, your next step is to put the cmp, ckp and activate the actuator solenoid off idle to build some oil pressure.
You should see the cmp advance or retard in relation the the ckp, when you activate the actuator.
Ray
Ray
Ray I only have a 2 channel snap on scanner. Im constantly looking at the pico website. Like a kid in a candy store. What are your thoughts on the pico sets?
Make sure that you buy the Pico scope from Autonerdz, because they have a free website, if you buy from Autonerdz, that has a series of training videos on how to use the scope properly.
If you buy a PIco from another supplier, you will not be able to access the full Autonerdz website, that has the training videos.
If you have a problem or a question, the Autonerdz guys will help you as they have helped me over the years.
You can also post questions in the Forums, myself and the guys will help you, with your problem vehicles or your scope questions.
Some engines have 4 cmp sensors and a ckp, so you can think about getting an 8 channel scope
Ray