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Poor original poster ILV2RK, this discussion has gone way beyond his original inquiry. Most people do not know the intricacies of scanner programming and don't plan to. ILV2RK, the 4.2 VVT is notoriously sneaky to diagnose. It could be the chain, too. I would recommend adding marvel mineral oil to the engine (half a quart) —sometimes the VVT valve itself sticks due to the oil screen on it clumping up.
 

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Maybe I'm too simple, but considering what he's already changed, it seems to me like there's only a few things left - worn timing chain and/or tensioner (though I can't imagine anyone would change one without the other), bad crank sensor (or needing calibration), and/or bad/worn timing sprocket. Crank sensor = easy, the other two, not so much. I wouldn't replace the chain/tensioner/sprocket without testing for sure, considering the labor cost if a shop does it, or time if it's your labor.

I know the sprocket can be changed without having to remove the timing cover if you have the right tools that hold the chain up and under tension while you replace.
 

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2002 chevy trailblazer_lt
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Most people do not know the intricacies of scanner programming and don't plan to
The purpose of that excursion was to point out the fact that you can record and see what is actually happening with the camshaft timing for less than a $20 dollar investment. Desired cam angle, actual cam angle, variance between the two and duty cycle of the solenoid. You can easily record a half hour or an hours driving and see what is actually happening with the cam. Is it failing to open quick enough? Is it failing to close quick enough? Actual data gathering and analysis as opposed to random guesswork. For less than $20.
 

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2005 buick rainier
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Agreed, what I post is simply intended to give users an inexpensive way to obtain some data they would otherwise not have access to. The proliferation of inexpensive adapters and smartphone apps makes it simple (somewhat) to even record driving session data for capture of intermittent faults.

So now, PWM is handled in SAE J1850 VPW messaging as a single byte hexadecimal value in the range of 00 to FF where 00 is 0 percent and FF is 100 percent. When you press the button on your Tech 2 scantool or equivalent it sends a message requesting device control for the selected output with the desired value encoded therein. As a quick example I have a button configured to send a command instructing my cooling fan clutch to engage at 37.5%. looks like this...

View attachment 56517


The first string sets my message type as a node to node message from the default scantool address of F1 to node address 10 (PCM). The second string is a device control request with the various parameters required to set the PWM at 0x60 which is 37.5 percent.
Op has already blasted the parts cannon & consulted the local "mechanic" for advice. Sounds like he has exhausted his silver bullets. Either pay a reputable shop to make the diagnosis or learn how the system works. As a seasoned journey level mechanic I would not expect a DIY'er to comprehend the totalatility of the systems and those related but it might keep someone from wasting money on unrelated parts.
 

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Re: The purpose of that excursion was to point out the fact that you can record and see what is actually happening with the camshaft timing for less than a $20 dollar investment. <— it probably is very useful, but unfortunately its a realm few people are skilled/knowledgeable about.
 

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Other idea is the phaser at the end of timing shaft. Mine did go bad at one point. A $900 repair. A leading problem with the 4.2 engine is overall lack of access to the chain and all related components. Getting to the components could be a manageable but still difficult job on a 2wd model, but is an absolute and torturous nightmare on a 4wd model. The kicker is, the front plate on the 4.2 engine is attached to the bottom of engine by ONE small bolt and is covered by the oil pan. (To maintain overall oil pressure integrity i think...) If the front plate could be taken off independently of the oil pan it would make a world of difference in accessing all the 4.2’s timing chain components including the tensioners down around midpoint.
 

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2007 chevy trailblazer_ltz
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My '07 TB finally died a hard death on the side of the road last May with 232K miles, threw a rod and flattened the #4 spark plug. All I can say is that once I reached 100K miles with this engine it was notorious for a loss of oil and constant P0014 codes and idle surges, primarily because of the sensitivity to the low oil. Just kept checking the oil level to avoid the problem......I miss that car........
 

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232k? Thats hell of a run! @170k, I sort of expect a major engine failure past 200k. They're good when running well but aren't “million mile” engines. Perhaps could be if things on it were more serviceable.
 

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2002 chevy trailblazer_lt
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Yes. Trans rebuilt at 226xxx miles.
I'm at 310K with an engine rebuild @ 252K. This scanner thread has been very educational for a beginner like me (electrical). What blue tooth scan tool would you recommend for $24.00? AMZ has BlueDriver and OBDLink MX for $99.00, which are Prof level tools.
Good investment if one is willing to punch above one's weight class?
 

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2002 chevy trailblazer_lt
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I currently like the VeePeak Mini. Just bought a second one. I have a total of 5 Bluetooth Mini OBD adapters.



The Bluedriver DOES NOT work with apps like Torque, Car Scanner, OBD Fusion etc. Bluedriver is limited to their own proprietary software. I believe the OBDLinks are good products but have no first hand experience with them.

An additional disclaimer would be I deal ONLY with early GM vehicles before CANBUS came on the scene so I have zero knowledge of how these may work with CANBUS networks.
 

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2006 Chevy Trailblazer_LT, 4.2L L6 Engine
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Discussion Starter #36 (Edited)
Just a couple of questions from me. What brand or brands of VVT solenoids did you use? What brand of camshaft position sensor did you use?

How does the electrical connector that plugs into the VVT solenoid look? Does it feel gooey as if it is decomposing? Where the wires go into the plug, are they secure, are there any gaps between the wire insulation and the plug body?

How often are you changing your oil and oil filter and what weight of oil are you using?
I know this is probably gonna throw a red flag but i used Duralast (Autozone House Brand) for the 2 sensors.
Oil & filter get changed every 3000 - 5000 miles with 5w30.
Harness and wiring look OK. It is original but still looks alright.
 

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2006 Chevy Trailblazer_LT, 4.2L L6 Engine
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Discussion Starter #38
On scan tool can command vvt solenoid on with engine running.....look at actual and desired as you increase percentage and also a data pid variance difference between actual and desired. If that doesn't move electrical checks would have to be done at vvt solenoid. If pcm control and ground circuit are good then have to look at cam position sensor in response to vvt solenoid movement. Small oil passages can get clogged. Oil quality and pressure important. Hard to test without proper testing equipment. Oil pressure good.... Any engine noise... What if any driveability problems are you having.
Oil pressure seems good and no engine noise.
When starting engine on a cold start, it runs very rough at first for 10-20 seconds and then settles down.
Seems a little sluggish and occasionally has a bit of rough idol at stops but not often. Better after changing all coils.
I did recently purchase a Foxwell NT510 Elite Bi-Directional scanner with the GM software. I know the basics but it does way more than I know.
Has very poor directions for all features.
 

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2002 chevy trailblazer_lt
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I currently like the VeePeak Mini. Just bought a second one. I have a total of 5 Bluetooth Mini OBD adapters.



The Bluedriver DOES NOT work with apps like Torque, Car Scanner, OBD Fusion etc. Bluedriver is limited to their own proprietary software. I believe the OBDLinks are good products but have no first hand experience with them.

An additional disclaimer would be I deal ONLY with early GM vehicles before CANBUS came on the scene so I have zero knowledge of how these may work with CANBUS networks.
SOLD!
As an example, I viewed a YTube intro to OBD Fusion. $5 bucks more for the app and, FOR BEGINNERS, you can create a dashboard that displays LIVE readings to your smartphone! That's a solution to Fuse 24 dashboard short for less than $20.00! And THAT, my friends, is dessert before dinner!
Amazon can't deliver till next Fri, but I'll keep you posted. That is, if anyone's interested...

56532
 

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An additional experience I had with OBD Fusion. I was using the app in an unconventional way, doing a direct memory read of a TCCM module and had some difficulties. I emailed their tech support and had a prompt reply and was able to work through the issue with their assistance even though what I was doing was outside the scope of their design! Anyone who has ever tried to get any manner of support from the Torque developer knows the futility of that endeavor!
 
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