'02 Toyota Highlander and P340 Cam Code

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'02 Toyota Highlander and P340 Cam Code

Postby hexibot43 » Fri Nov 22, 2013 1:09 am

Had a fun one today. An '02 2WD Toyota Highlander with a 2AZ-FE 2.7l 4 cylinder, with an automatic was giving us some trouble with diagnosis. This vehicle came in with a blown head gasket. And I mean blown. I'd never seen one where it was blown so well gases were coming out the side of the block where the head and block surfaces met. All the threads for the head bolts had been pulled out. A common failure on this motor, but I'd never seen one this bad. Usually we can just re-tap the threads and all is good. The head went out to the machinist who confirmed this engine was going to be un-repairable. A Reman. engine is installed. We find two of the ignition coils had been damaged in the overheat, and so replace all four coils. The vehicle is now running very well in the stall, and on the road. Only problem we now have is a MIL illuminated with a code P0340 - Issue with Camshaft position sensor. We decide to just put a new Cam sensor in which sits at the back of the head figuring it would likely have been just as easily damaged as the Ignition coils. No dice. Still an MIL. We then went to Identifix to see what was common as a failure with this code, and found that more often the problem was a bad crank sensor and not the cam sensor. The Crank Sensor was replaced with the same idea as when we had changed the Cam sensor thinking the heat could have damaged it as well. Still in the same place. MIL illuminated and no closer to a fix.

We finally hook up the PicoScope to take a look at the two patterns, thinking perhaps there was a timing issue between the cam and crank sensors.

CamSensorWaveformIssue.jpg


I have to be honest. I couldn't see the problem with the pattern right away. We didn't have a known good pattern to use as reference. I finally found an image to use as a baseline this morning. https://www.youtube.com/watch?v=vrmuhgQteCU We had a missing (weak) signal. We then pulled the Valve cover to find on the end of the camshaft there are three dowel pins that make up the three humps of the camshaft wave pattern.

IMG_20131121_142858.jpg


You can see the three dowel pins. One of the pins had been pressed in to far creating an excessive air gap! We then measured all the pins on the old cam, which we confirmed were all of equal height. Next we reset the heights of all the dowel pins on the new cam. Put it all back together, and presto we got a good wave pattern and no more MIL.

CamSensorWaveformIssueFixed.jpg


Notice the amplitude on all three humps of the Cam sensor wave pattern match.

I'm really wondering what we would have done if we didn't have the scope. I am still thinking how we could have caught this one without it. a DVOM would not have helped. And to be honest I don't think a cursory look of the dowel pins would have stood out either. You had to first know there was a problem with the waveform to go looking for an issue. The difference between right and wrong just wasn't that much. And so ends my first Case study.
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Last edited by hexibot43 on Sun Oct 26, 2014 2:32 pm, edited 1 time in total.
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Re: '02 Toyota Highlander and P340 Cam Code

Postby Neilcur » Fri Nov 22, 2013 8:28 pm

Nice result and shows how a scope can show you what is really going on!

Not having a go at you but why when you had a scope didn't you scope cam and crank supply,signal and ground signals before you changed the sensors as this may have prevented the new parts being fitted as they were not needed?

Thanks Neil
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Re: '02 Toyota Highlander and P340 Cam Code

Postby hexibot43 » Sat Nov 23, 2013 4:22 pm

Neilcur wrote:Nice result and shows how a scope can show you what is really going on!

Not having a go at you but why when you had a scope didn't you scope cam and crank supply,signal and ground signals before you changed the sensors as this may have prevented the new parts being fitted as they were not needed?

Thanks Neil


Firstly, I thought it better to keep it honest. And now I am realizing I hadn't been. I did scope it earlier on, but the images that look so obvious to me now were not then. I hadn't yet found the youtube video that showed me the three hump Cam sensor signal. I had no idea what I was looking for until I saw that. In the beginning we had a waveform I had captured. A code. And what I was able to find on Identifix. And honestly no idea how the cam waveform was derived, and so didn't see issue with it. Once I watched the You tube video it was stabbing me in the face. We then pulled the valve cover to see three dowel pins. We knew what was wrong the moment we saw that. The puzzle was complete. We were also quick to change those parts, and probably should have just done it when the new motor was fitted. That motor got hotter than any motor I'd ever seen before. So hot that two coils were ruined.
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Re: '02 Toyota Highlander and P340 Cam Code

Postby Steve Smith » Mon Nov 25, 2013 11:40 am

Hi and thanks for taking the time out to post this study. The information is invaluable as was the use of the scope, much appreciated.
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Re: '02 Toyota Highlander and P340 Cam Code

Postby evanlip » Fri Jan 02, 2015 11:55 am

hi,im a new user of scope,after looking at your case,i feel more confident diagnose with scope,and continue to study more n more about scoping.
yes,u were right about this model engine is so famous of this cynlinder head bolt issue.
thanks for your post.
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Re: '02 Toyota Highlander and P340 Cam Code

Postby hexibot43 » Thu Jan 08, 2015 2:33 am

You are very welcome.
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Re: '02 Toyota Highlander and P340 Cam Code

Postby sigoaprendiendo » Thu Jan 22, 2015 3:14 pm

Yes, thank you very much again.

Now We have a good reference waveform to compare with, very valuable information that for sure will help us in our daily diagnostics. :D

If I understood right, the first and second humps are 180 degrees away each other and both have to be 90 degrees away from the missing teeth. Right? :roll:

Kind regards

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