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Signal to VCT solenoid?

5K views 13 replies 6 participants last post by  SD_Rider 
#1 ·
I have a cam timing advanced code.

My mechanic's troubleshooting found that the square wave signal to the VCT solenoid dies after (what seems like) the car warms up. It then goes to a constant 12V state.

If you shut the car off and restart, the signal returns but quickly goes away. He showed me and I verified what he was seeing.

The mechanic thinks that the computer is bad....any thing else to check???

For troubleshooting purposes...If I go to the local auto yard, can I just pull the computer from an SVT and will it be plug & play?
 
#3 ·
It had a timing retarded code, then the t-belt was changed, and now has a timing advanced code.

I also have installed a new VCT solenoid.

The mechanic says he has tested everything. I visually watched as the car warmed up and the square wave dropped out.

He said the signal is from the computer and is not affected by anything else. I am thinking of having the dealer verify as well, but have never had good luck at dealers....always feel like I'm getting ripped off. :/
 
#5 ·
The signal from the ECU is an output. There has to be an input controlling it, namely the Cam Position Sensor.
Log the Cam and make sure it's still reading when the VCT drops out. If it's not the car will go into a failure mode and run on known good values. Which means the VCT is good.
That may point to the cam timing not being done correctly.
 
#6 ·
Please be specific.
The VCT actuator is at the front of the engine, the timing and accessory belt side of the engine.
The VCT sensor is at the rear of the engine on the transmission side.
The actuator should not have a signal unless the VCT is actually commanded. At idle, the VCT is NOT commanded, so there should be no or a small signal.
The VCT sensor is a hall efect sensor that produces voltage every time the position sensor wheel passes. There are 3 tabs (I believe) that pass the sensor every rotation.
If the engine speed is low the change in signal can be seen easily, but at higher engine speeds, like a quick rev in neutral, unless you have some pretty high accuracy reader (a volt meter will NOT likely ready the voltage changes, an o-scope would work) the meter will miss the voltage changes. Doing the math, at 2000 rpm /2 for half speed of the cams, and 3 tabs on the encoder you have 50Hz, which is pretty fast...

Just want to be sure you are getting the correct measurements...
 
#10 ·
There are several parameters that you can look at to determine what the VCT is doing and the adaptive values for the cam timing. If you log the commanded and actual VCT angle you can see if it is moving. There is an adaptive term that corrects the encoder wheel on the cam (the strategy assumes perfect cam timing) and the difference is accounted for in the strategy. The adapted value must be within +- 3 degrees of correction before you will set a code.
 
#11 ·
If the problem showed at changing belt I'd bet a million timing still off a bit. VCT is some kind of sensitive sh-t. The older Contour guys used to have fits with it too, but after changing VCT parts all over the map, 95% of the time it all got back to timing that belt.
 
#12 ·
The problem showed when I bought the car! lol!

No, seriously...it had multiple codes when I bought it....well...as I drove down the freeway after buying it. Yeah...I was scammed. But, that's in the past and the next step is move forward.

I talked to a mechanic friend-of-a-friend and he thinks he can figure it out. Going to drop it off next week. With mid-terms and visitation with my kids, I just don't have the time.

Wish one of you knowledgeable mechs were local. I'd slip you a few bucks for your time. :)
 
#13 ·
The VCT doesnt work below 1700 rpm , the VCT gets its info from the Cam sensor , load , RPM , engine temps etc

The VCT makes it changes primarily from load vs rpm

It sounds like to me that the cam timing is off and the VCT is giving up trying to correct the over/under advance , if your getting that code after changing out the belt my guess is out of time on the VCT gear and cam

Tom
 
#14 ·
Thanks!
I'm not getting emails for some reason...

Literally just checked the forum this week. :/

I had another mechanic look at it...after more money paid, he checked the timing twice and he believes that the phaser is bad. Looking on the forum, there has only been one (that I can find) that took it to the dealer and had the intake cam sprocket replaced.

Anyone have a known good one lying around??? :)
 
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