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Discussion Starter · #1 ·
Full OBDII description in title.
Finally addressing a code that for a couple years came and went. Now it shows up quickly after clearing the code and starting the engine a couple times.

As far as I can tell the engine does not make any irregular noises though I'll admit, the P0016 code started to come around more as I had put off an oil change last year - wonder if doing that compromised a part.

Yesterday afternoon I was looking under the hood trying to spot anything obvious. All I could think to do was to verify that the cam sensor was getting power and ground and make sure there were no leaks anywhere around the engine. That all seemed okay.

Doing research into the code points me towards several possible problems though none of them are obvious for my situation. So I'd love some help finding out what's wrong and how to fix it without just throwing parts at it and see if I get lucky.

The engine is over 150k miles now. Idles at 600rpm without any suspicious noises. I'm curious to check out the screens and sensor socket of the VVT solenoid but from what I've read there are other codes that point directly to this part causing the trouble, and I don't have those knocks on wood. I might just inspect and replace it anyways since the engine is over 150k miles now.

What else should I look for to fix this P0016 code?

Thanks!
 

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I'm really a wet blanket for these VVT and TPS/TPP problems when they come at the same time as the PCV not working.

I've had 2 friends Voyagers in my "shop" (I'm retired but they come anyway) and most of the troubles as I've run into them are caused by water getting into the lube oil which is actually condensate from (ahem!) the PCV not working.

You cannot have water running around inside an engine and just blithely get away with it - not for long anyway.

Damage to the VVT in the form of "freezing" in one position because it's especially easy to damage from rust --- and the throttle plate sensor and the actual camshaft/followers are very susceptible to water intrusion.

Got slime inside your 710 cap?​
Got slime on your dipstick?​
Got brown milkshakes in the sound deadening chamber before the throttle plate?​
Did you install a cold air pack and eliminate the CV side of the PCV?​

These are only the tip of the iceberg and if you have any of these conditions, then you're slowly killing your engine.

The first time this P0016 problem shows up - it might be very intermittent - then more often - then all the time.
 

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Discussion Starter · #3 ·
Hey thanks for the reply. Every place I look for ideas on the problem seems to lead a daunting job. I'd be without a vehicle for a while if it turns out to be the timing chain or a gear.

I had replaced both cam and crank sensors over the weekend. The code came back quick. Would have done the VVT but it didn't arrive in time. I'm going to replace that and do an oil & filter change tonight. Really hoping this clears the issue because all that would be left is the chain, a gear or the PCM itself.

Worth noting, I did have light grey sludge on top of the oil cap when I did finally do the oil change. Not only that, but not much oil came out and it was very dark and thick.
But since then there hasn't been any sign of the stuff. Wondering if it had gunked up the VVT and finally did it in. But I figured that would throw other codes if it were the case. Only one way to find out.

On the plus side, changing those two sensors and doing a idle relearn may have improved the engine's performance. There is noticeably less hesitation in acceleration.
 

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I had replaced both cam and crank sensors

Not certain , but if you replaced fhe crank sensor and did not do the required Crankshaft Angle Sensor Error relearn it very well might exacerbate the problem.
 

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A curiosity... your previous posts indicate you have an 04 4.2. As far as I know the 4.2 does not have a code P0016. The 5.3 and 6.0 do. What are you reading this code with???
 

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Discussion Starter · #6 ·
What makes you think my car couldn't throw a P0016? The description of the code is from data between the two sensors I've replaced. Not only that, but I'm not alone in the world owning a 4.2L with this code.
I use a cheap obd2 reader from Walmart.

From what I now understand, I need to do a CASE relearn and need a bidirectional tool to do so.
 

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Discussion Starter · #7 ·
Yesterday I had replace the VVT solenoid, oil and filter. Learnt that when I did an oil change less than a year ago my dumb ass didn't pull the oil plug... I'm a relatively new driver and big into DIY. Though I'll admit that isn't much of a defense for that mistake :rolleyes: Live and learn.

Anyways, the part had a little gunk on the screen covering the middle section. It wasn't too bad but still something I wanted to check off. I have the suspicion that this part had already been replaced once before as it was 100% identical to my ACDelco replacement. Thought it being a 2004 would have the older style part without the rings on the screens.

I know I need to do a CASE/crankshaft relearn. There's conflicting information all around the internet which is what made me believe I could go without it or try a manual relearn - which no one seems to have successfully done, only shared how scary it was trying on the highway.

Since I'd much rather do the work myself, I'm having a hell of a time finding a reasonably priced & functional bidirectional scan tool that can do crankshaft relearns. I'd rather not haggle with a shop to do this for me but I just might have to. I'd prefer to invest in a tool so long as it doesn't cost me over a few hundred dollars. Any recommendations?

My engine runs soooo much better now after the work noted in this thread. Just need to get this SES light out for inspection.
 

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What makes you think my car couldn't throw a P0016?
Two things. First from the service literature indicating it is for the 5.3 and 6.0..

57168


Secondly, when I ask a PCM for the status of DTC P0016 using a service 17 request I get a response indicating that the request is "out of range" ie: not supported. I then ask for DTC P0014 and get a positive response indicating the request is valid . seen here...

57169
 

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Discussion Starter · #9 · (Edited)
That's strange....
Could you send me a copy of the service literature you're referencing?

I'll have to try another scanner and see what it shows... I didn't think there was a even a remote chance of getting mistranslated codes... In fact, I haven't come across any example of that chance during my countless hours of researching the code, or any code for that matter.
 

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Discussion Starter · #10 ·
Hmm... someone else had the same issue (same year and model) but a member suggested the thermostat?......

I'm definitely confused.
 

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Discussion Starter · #11 · (Edited)
And another, an oil change fixed their issue;

For the record, in my case here the code was intermittent and finally stuck on after prolonging an oil change and then failing to do one completely. I've been using Mobile 1 5W30 full synthetic high mileage oil.

Another question;
Not certain , but if you replaced fhe crank sensor and did not do the required Crankshaft Angle Sensor Error relearn it very well might exacerbate the problem.
As usual there are mixed answers around the internet about this but most folks say a CASE relearn is absolutely needed. Wouldn't there be a specific code (P0315 I think) indicating that a relearn is needed? Or even perhaps obvious by the performance of the engine (which has only improved for me)??
 

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From what I have read it seems the CASE relearn is absolutely needed as far as GM is concerned. It may set a specific code without it or it may not. It seems to be that the crank position sensor may be ever so slightly affected without the error correction and may have trouble detecting misfires specific to any given cylinder. Now is the error enough to cause some other crank position code I do not know, but suspect it may add to such an issue.

I have an 02 that uses the same PCM. That is what I am using to verify that the P0016 is not supported. I must say that I have never scanned an 04 and that may have a software update that enabled that code, but the service literature I have seen clearly notes it is for the 5.3 and 6.0. HOWEVER, contrary to that 9854 page document I have seen a listing on a gm site that DOES show a P0016 for a 2004 ll8 engine. I think next time I am at the upull I am going to have a chat with a 2004 ll8 PCM!!

So assuming you do have an issue that may be due to neglected maintenance (lack of proper oil changes) perhaps just more frequent oil changes with synthetic oils and give it some time to see if it clears up. When first I got my 02 back in 2010 I would occasionally get a P0014 code. After more regular oil changing it stopped. I'm fairly sure I still have the original VVT actuator at over 285 thousand miles.
 

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Having never done a Case Relearn Procedure myself, I went to Dr. Google and asked him.

Here's a C/P from a site that tells of a way to get it done without a scanner.



NOTE: If the Crankshaft Variation Relearn is not accessible through a scanner (some truck applications 1998 & later), perform the relearn in the following manner:
  1. Turn off all of the accessories. With the Air temperature sensor and Coolant temperature within 5 degrees (Centigrade) of each other, start the engine and let it idle in Park or Neutral for two minutes.
  2. Accelerate the vehicle to 55 mph at part throttle. Cruise at 55 mph for 8- 10 minutes until the engine reaches operating temperature.
  3. Cruise at 55 mph for another 5-6 minutes.
  4. Decelerate to 45 mph without using the brakes, and maintain 45 mph for 1 minute.
  5. Perform 4 deceleration cycles, without using the brakes, of 25 seconds each where no specific speed is necessary. Returning to 45 mph for 15 seconds in between deceleration cycles.
  6. Accelerate to 55 mph and cruise for 2 minutes.
  7. Stop the vehicle and idle for 2 minutes with the brake applied and the transmission in Drive (automatic trans.) or Neutral (manual trans.) with the clutch depressed.
_

This is amazingly like the E40D-E transmission relearn procedure when the KAM was lost due to a dead battery - or in the case in which I was engaged --- they were using a main electrical shutoff that chopped ALL the power from the battery to the whole vehicle, including the ECM.

The idea was to have a fully charged battery that had not been sucked down by computers constantly nibbling on the battery. They needed those ambulances to start - first time - every time.

The problem was they were also dumping the volatile memory that performed the adaptive shifting procedure that would burn up the overrun clutch and shoot the dipstick out so hard it would put a dent in the hoot and blow the ATF all over the engine.

A few ambulances burned to the hubs from the ATF hitting the cat or a super hot manifold and--- sizzle!
 

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Discussion Starter · #14 · (Edited)
Thanks for the replies, guys!
I'd bet it is due to bad oil as well. But I have to check everything off before I continue. I had tried another scanner last night and I see the P0016 code is pending at every startup - unlike before when it would take months, weeks then days to reappear.

I've seen that relearn procedure around quite a few places but had not found any follow ups proving it's success, only failing and describing it as a scary task to try on any road. But I'll give it a try when I can!

I have the thought of monitoring the cam and crank sensors with my portable oscilloscope. If I understand correctly I should be able to view the correlation of the timing between the two to see if it's indeed off enough to trigger the P0016 code. If it's noticeably bad I'll have to remove the valve cover and take a look at the actual chain alignment and check for stretching or loose parts.

Using my scope I believe I should be able to rule out the wire connectors or the PCM itself.
 

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This description of the circuitry on a late model might help, though the numbers of crank and cam pulses are different on yours. I suspect the general idea is the same.

Screenshot_20210610-074903.png


Screenshot_20210610-075334.png
 

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This description of the circuitry on a late model might help, though the numbers of crank and cam pulses are different on yours. I suspect the general idea is the same.

View attachment 57172

View attachment 57173
Hmmmm ..? I take exception to that info as to being golden.

I had driven my 4.3 Astro Van for years with 18.8 MPG and never saw any other value ...this is in a Cal/EPA regulated vehicle.

Just for kicks, I scanned it and saw the camshaft ovvset base was - 36° (ATDC). HELL! That's where the crappy mileage is!

I very gingerly tried the Crank Position Relearn and the retarded condition didn't change a bit.

No wonder ... the distributor was locked to not be adjustable .... but I fixed that by grinding the hold down and reset the base timing to 0° BTDC.

The fuel mileage jumped to 24MPG .... INSTANTLY.

OK ... there's a moral here ... I did this Relearn Procedure on an engine with 214,000 miles on it. Ewwwwwww! Scary stuff!

I had visions of pistons swapping holes, rods trying to see sunshine, chains wrapping around the alternator and water pump trying to suck them into the timing cover.

In truth, I've done this procedure to so other, older engines... and even when you hit the fuel limiter(*) ... the engines have never grenaded.

At least, not yet.

(*) If you've got your dog in this fight, hitting that limiter can make you wince in apprehension --- but if you don't actually HILD the throttle there, you'll likely be OK.
 

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Discussion Starter · #18 ·
I'm trying to find details for expected crank and cam pulses for my 04 so I can make sure the math checks out. I'll have to keep digging.

Just adding for reference, another P0016 thread from a while back. Luckily we have different issues along with the code knock on wood again

Most of those threads are 2004 LT models. Hmm...
So that's two P0016 threads with a good ending. Let's hope this becomes another lol
 

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Discussion Starter · #19 ·
This bit will be helpful for sure (also from another 2004 TB P0016 post from another forum);

"P0016 CHEVROLET - Crankshaft Position - Camshaft Position Correlation Bank 1 Sensor 'A' ...Possible causes; Mechanical timing fault (stretched timing chain or damage timing chain tensioner), Blocked oil passage, Low oil level, Faulty Intake ('A') Camshaft Position (CMP) Sensor, Faulty, Crankshaft Position (CKP) Sensor.....If this DTC started after recent internal engine repairs, inspect for proper engine mechanical timing. With the camshaft cover removed and the #1 cylinder at top dead center, make sure that the darkened chain links are lined up with the alignment marks on the exhaust and intake cam sprockets. If a P0016 is resetting without any engine performance concerns but the above information did not isolate a cause for the DTC, replace the Cam Phaser Actuator sprocket....The Powertrain Control Module (PCM) has detected the actual Camshaft Position (CMP) Sensor angle of one camshaft is greater or less than the commanded state. Possible symptoms, Engine Light ON (or Service Engine Soon Warning Light) Engine hard to start, Engine stall while driving. P0016 CHEVROLET Description; The Crankshaft Position (CKP) sensor is a permanent magnet generator, known as a variable reluctance sensor. The magnetic field of the sensor is altered by a crankshaft mounted reluctor wheel that has seven machined slots, 6 of which are equally spaced 60 degrees apart. The seventh slot is spaced 10 degrees after one of the 60 degree slots. The CKP sensor produces seven pulses for each revolution of the crankshaft. The pulse from the 10 degree slot is known as the sync pulse. The sync pulse is used to synchronize the coil firing sequence with the crankshaft position. The CKP sensor is connected to the Powertrain Control Module (PCM) by a signal circuit and a low reference circuit. The Camshaft Position (CMP) sensor is triggered by a notched reluctor wheel built into the exhaust camshaft sprocket. The CMP sensor provides 6 signal pulses every camshaft revolution. Each notch, or feature of the reluctor wheel is of a different size for individual cylinder identification. This means the CMP and crankshaft position (CKP) signals are pulse width encoded to enable the PCM to constantly monitor their relationship. This relationship is used to determine camshaft actuator position and control its phasing at the correct value. The PCM also uses this signal to identify the compression stroke of each cylinder, and for sequential fuel injection. The CMP sensor is connected to the PCM by a 12-volt, low reference, and signal circuit."
 

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Discussion Starter · #20 ·
Here's a page that has scope shots of a 4.2 comparing bad timing to good.

I'm waiting on some accessories for my oscilloscope and will post screenshots over the weekend.
 
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