Signal wire shows 12 volts... ignition off

[halfawhole again]

Y'all be gentle now? At least give me the opportunity to give ya a chuckle with a few stupid questions first.
My 03 trailblazer has been giving me fits for months ...again. The first time I was ready to junk it ...until I finally learned how to test a coil pack? It quickly turned to praise after finding 3 weren't up to par. Pretty much gunna keep her forever now!
But she's throwing 1345s...which you don't need a code reader for that...it's pretty apparent... Also a 0340... I'm guessing cause the signal wire reads 12 volts...switched on or off. It does drop down to 1.something when face to face with a rachet... So I can't stress the fact that I'm not a mechanic... But I didn't see anything wrong in that little 2 ft wire... I stripped off the black tape just about to the PCM...stopped where the wires meet from all over at the bottom.
And I'm am suffering from information overload... The internet is a little too full of information...most not pertaining to my current cause? But you have to wade up to your knees in each stream before you find out if it's helping ..
I'm still tripping on oil not being just a lubricant anymore... I'm from the era when the older a car got...the thicker the oil you fed it... This variable timing ... 5 volt sensors...and 0w 20 (cooking oil?) Is really way too much to cram at midnight out in your driveway? I just know...I love my trailblazer... Im finally up out of the head light zone( if you own a car... everybody's headlights are at eye level or more...tired of looking at bumpers and brush guards that are clearly just gunna run right over my ass and not even feel a bump) and the 4.2 delivers adequate horsepower/ mpg...
And I know there's guys here that have ate shit like this ... breakfast lunch and dinner for the last 20 years that ARE the repair manuals... So...could you please? Point me in the general direction? Is it really short to ground...cause it is a "short" wire...or is like something pinched in the liftgate? Or something equally impossible to think of? Except for you guys? Oh...and sorry about my diarrhea of the thumbs? I don't get out much?

 

[mrrsm]

Welcome to GMT Nation...

You are correct with the idea that using a Code Reader in the case of discovering the two related issues with the P1345 and the P0340 Codes are concerned will NOT help you. However, to go further you WILL require either an Oscilloscope or a LabScope to perform a better Visual Diagnostic Procedure. This Link leads to a more precise description of this Problem:

P1345 – Crankshaft Position-Camshaft Position Correlation (GM) – TroubleCodes.net

www.troublecodes.net

Those Codes are intimate with the problem of having a Stretched Timing Chain on a High Mileage Engine that causes a Mis-match between the signals coming from the Crankshaft Position Sensor (CKP) Sensor vs. the Signals coming from the Camshaft Position Sensor (CMP). The PCM incorporates BOTH signals in deciding WHEN to Fire the Electronic Fuel Injectors...just before initiating the COPs (Coil Over Plugs) to Fire Off the Spark Plugs. As with everything else in Life... Timing... is EVERYTHING.

The Camshaft Phaser mounted on the front of the Exhaust Camshaft (Passenger side of the Upper Motor) has Three Narrow Notches and Three Wide Notches cast into it that are used for showing the PCM the Absolute Position of the Camshaft within a Range of 0-25 Degrees of Retardation using Pulse Width Modulation (PWM) in order to control "The Works".

Observe that in this next Diagram, The Blue Arrows point at the (3) Narrow, Hall Effect Notches in the Cam Phaser... while the Red Arrows Identify the Wider (3) Notches in the Cam Phaser. The Purple Arrows point at the Two Timing Chain Guides... while the Black Arrow points out the position of the Timing Chain Tensioner:



In a Nutshell... When the White and Black Nylon-Plastic Inserts of the Timing Chain Guides WEAR IN...and the Timing Chain Tensioner Plunger Fully Extends OUTWARDS... Then the relationship between the Cam Phaser Sprocket and the Smaller Crankshaft Sprocket CHANGES just enough to THROW OFF THE ENGINE TIMING and ruin Compression and Spark Timing enough to cause the Engine to STAGGER AND STALL.

Observe THIS Video from "The Car Doctor" and note the Edited Image Screen Prints below are Video Excerpts useful in the follow on explanations:

The use of an Oscilloscope to perform THIS Camshaft Signature Test will reveal any discrepancies caused by these Mechanical Problems.


As per "The Car Doctor's" Video... THIS Image shows a NORMAL Camshaft Cam Phaser Signature Test:



THIS Image shows an ABNORMAL Camshaft Cam Phaser Signature pointed out with a Red Arrow:



THIS Image shows another ABNORMAL Camshaft Cam Phaser Signature pointed out within the TWO Red Arrows. Note the Corruption in the Wide Square Wave Signal:



When the Cam Phaser Square Wave "Timing" (Shown here in GREEN for the (CMP) Signal) is aligned on the Oscilloscope Screen along with the (CKP) Crankshaft Signal... (Shown in BLACK for the CKP Signal) ...you can see an excess number of Sine Wave Peaks and Valleys (around 5-6) indicating that the Timing Chain has S-T-R-E-T-C-H-E-D... as there should ONLY be around 4 SINE WAVE Peaks and Valleys in between the "S" Break and the Leading Edge of the Green Square Wave of the Cam Phaser:



THIS Type of Test is Definitive for having a Stretched Timing Chain ...which requires a Great Deal of Mechanical Skill ...supported by @Mooseman's Epic Thread on How to Perform THIS Timing Chain Set R&R Procedure.

How to replace I6 timing chain and tensioner

This is the last of several articles during my work to replace the timing chain and tensioner. How to replace the I6 timing chain and tensioner. Difficulty (out of 5): 8 (I'm not kidding) Tools required: Assortment of wrenches, ratchets, extensions, screw drivers. Socket sizes: 7mm, 8mm...

gmtnation.com

 

[halfawhole again]

I have came across this answer in my travels... That's a 20 hr. job... For a qualified mechanic... I have successfully replaced the timing chain tensioner in a wv jetta... To this day I can ...grasp how it stays there in place... there's just a tiny indentation you can feel...and you position it there and tighten the bolt...and it just stays? On flat metal? With just a dent? Man I studied for a month on that one...over and over til I was pretty sure I had it... My only flaw was the jack I used to raise the motor to remove the motor mount...it leaked down over the next day...so when I walked in after work the motor was all wop-sided and almost touching the floor one ...I feared the weight of it ...twisted like that might...warp something...but it was fine...we sold it after we had the blazer and fell.on hard times... My wife wasn't the only thing cancer took...it took our small.savings...anything extra we had...then things we needed...the trailblazer was a crucial piece in the fight...all her appointments were 60 miles away...we spent a lot of time in it... Lots of memories... I'm not ready to let it go...but that's almost $2000 ...into a motor with 300.000.miles. Looks like the smart move would be to invest that money into something with less ails... I've got my eye on a civic...doesn't run...timing belt they say...but I kinda know the owner and the car...it hasn't been mistreated...she only wants $200... The trailblazer can sit...and I can disassemble ... everything? Is there one part that doesn't come off during this procedure? Lol. Thanks for putting me back on the right path... Zack...on YouTube ...showed me the signal wire was a short to ground...that's what got me hoping that it wasn't as bad as I had though...

 

[Mooseman]

The P1345 may be a consequence of the P0340 because it can't make that correlation between the crank and cam.

So the P0340 is saying there's a problem with the cam sensor circuit. You inspected the wiring and it seemed fine. You could check the continuity from the sensor's connector to the PCM connector by following the schematics in the manual (check my signature for the link). If that checks out, you could just replace the sensor. It's cheap enough to do that (NTK or Delphi, GM is too expensive).

After that, see if both codes go away. If the P1345 is still present, it may need a CASE relearn, which requires a scanner capable of doing it, like a Tech 2 or Snap On.

Despite what @mrrsm may say, it's very unlikely it's the chain unless you have extremely high mileage or a failure of the chain tensioner or other timing component, which would be quite evident with noise. Another possibility though is the failure of the cam phaser. I had a P1345 twice on its own (no P0340) and both were failed phasers.

Fix the P0340 first then the P1345 if still present.

 

[mrrsm]

The OP's comment of "...but that's almost $2,000 ...into a motor with 300,000 miles..." puts an awful lot of Miles ...in his Rear View Mirror.

 

[Mooseman]

Our timing chain is quite robust and haven't seen too many fail or stretch to the point of needing replacement. They usually go to the scrap yard with its original engine. mine was probably fine. It was just the tensioner that failed but replaced it all as a "while I'm in there". I'd be looking at all the ancillary parts before diving into the chain itself. If it DOES need a chain, I'd probably be condemning the engine as at that mileage, it doesn't have a whole lot of life left.

 

[TJBaker57]

I would check the 12 volt power from the PCM at the sensor harness from the PCM. Then I would check the low reference from the PCM at the sensor location. Disconnect the harness at the sensor and read the resistance from the low reference harness terminal to frame or engine ground. It should be a very low resistance.

You say the voltage on the signal wire drops from 12.x to 1.x with a ratchet in front of it. The same should happen as the engine is slowly rotated by hand if possible. Not sure this is adviseable..... One would have to somehow disable any chance of the engine firing to do this. I think I have tried this once or twice but I really cannot remember. If I were at the house now I might try it.