Is it phasing?
I'm trying to figure out is the camshaft phased or is the cam gear off?
The crankshaft reluctor is a 58 tooth reluctor with a 12* reference window. Making each tooth 6*. Per service information my Intake camshaft can move 21*.
My known good capture Vs actual shows the camshaft on the scope to be off by 8 teeth of the crankshaft. 8 x 6= 48
If I'm not correct someone please correct me.
Make, model, engine and year would help. My telepathy is a little off at the moment LOL.
With out knowing YMM. My guess it’s a intake cam. Is the cam retarded or advance? Is the intake cam designed to advance? Is the engine a interference type? If it is not then you can jump the actuator and manually phase the cam! A lot of service info for cam phasing is in camshaft degrees. I can also think of quite a few that are in crank degrees.
"You don't need a “known good” capture. .....You already know there is a signal alignment issue. " Finally, somebody important said it! Thanks Jim. Aloha.
You too man. Hey, I got to meet Phil a few weeks ago. He stopped by my work, while here in Maui. That was fun.
Jim thank you for the feedback. You have made some very interesting points. I understand how the PCM sets this code. The issue I have is I'm not doing any teardown, I'm trying to prove failure. It takes more than just my word it's out of time when the engine has been torn down twice to confirm timing is not off. Your correct with these engines having multiple variations. I've not had an issue…
My late night thoughts after a brutal day in the office…
Excellent point Jim. I'd imagine we've all been guilty (I certainly have) of getting hung up on the details which distract us from the answer we seek. Sometimes it takes the perspective of someone outside the situation to alert us to that fact. That's what makes this forum so valuable and rewarding.
You said a few times that we could "test" for unintentional phasing.....how?
I recall a story, from you IIRC, (or perhaps second hand) of arguing with TAC that you needed more data on the scan tool and they said "no you don't, nobody looks at that". That would be a great new class from SMP. "Put down that fancy new scope and use your fffing scan tool!". One of the TBT guys put on a similar one, "stop wasting time with your scope".
Jim, Great points as usual. I have often said that there is no one that gets more out of GM scan data than yourself. I find myself using scan data more and more over scope shots lately on multiple manufacturers. Because of the scan data being so good and like you expressed the “known good” scan data element. I still like the wow factor of the scope and the story it tells don't get me wrong…
Hi John, 95% of the time scanner data and basic testing will confirm if an issue exists. It's that 5% that a scope is needed with multiple channels to pin down exact engine problems and dynamics. I watch Bernie with ATS on a regular basis and he is a scope wizard. The people that get in trouble are the ones that limit themselves to only a couple of channels. The ones I see have the most trouble…
Glenn, I agree with everything you are saying. I use one of my many scopes daily. I definitely am not a scope basher. It is not just your area with the shotgunning of parts. This is a national issue. Like I said there is a lot of interpretation in a scope pattern.
“” Remember when fuel pump amperage waveforms were going to change the diagnostic world. :) “” I do ! LOL
Matt; Good morning Sir. Depending on what scan tool you have you should have Camshaft PIDs, Desired, Actual and Variance. These PIDs should help you diagnose this vehicle. In Snap-on's platforms you should also have Functional Testing of the CMP Actuators to see if the phaser can move or not. I'm attaching a Training Article I wrote around GM's 3.6 Liter V6. I hope this helps.
My data PIDS for cam timing are all 0 with DTC active.
Yep, as it should be on a GM product when it is roughly the equivalent of 1 tooth off
Jonathan Yes, those PIDs are there, but of no use with the correlation DTC. They also have nothing to do with the actual cam timing. GM 101 since 2002 :-)
You're being mystic again. :-) Telling us that you know stuff that we DON'T doesn't really help. We didn't get that class out here. If desired and actual are not about cam timing then what are they about?
Sorry, I realize you are probably talking to ten people at once....I knew they all go ZERO with a DTC. But what does your statement: "They also have nothing to do with the actual cam timing" mean? What DO they have to do with, if not cam timing?
Actual cam timing would be related to the 720° rotation. Some OEs give you values in relationship to that. For GM, zero is park and where park is in the 720 rotation isn't stated.
Matt; I thought I'd also provide these pictures. This Chevy Malibu had been to several shops and the Timing Chain was replaced twice. The vehicle set codes for the Exhaust Camshaft being “Out of Phase”. Using and In-Cylinder Pressure Transducer we were able to see the Camshaft wasn't “Out of Phase”, so something must be wrong with the Reluctor's Position. In our case the Reluctor had “Spun”…
Is that 21° camshaft degrees or crankshaft? I would suspect crankshaft.
Good morning Matt, A couple of questions I have regarding this issue. As Jim mentioned, this code sets when the intake cam is either off or perceived to be off by the PCM when phasing isn't commanded. Besides that, what other conditons must be present for the DTC drive cycle to run? Did you scope the signals at various rpm ranges to see if the deviation remains constant throughout? Do you have…
I would think and in cylinder pressure transducer waveform test, in synch with an ignition event would capture this issue. If physical valve timing is the issue, it should be obvious when the cursors are overlaid to segment the total 720 degrees the represent the 4 strokes of the engine cylinder operation.
Bernie Thompson from ATS has a great video with phaser testing. The vehicle make is very different but the concept is the same. diag.net/msg/m4a5uy3bhd…