I have a p0016 code that keeps returning only when engine is fully warmed up and I apply the brake when coming to a stop, I replaced the timing chain, timing phaser, VVT solenoid, cam sensor , crank sensor, PCM, spark plugs, 7quarts oil to proper level and code still returns only when coming to a stop, runs perfect when cruising. Any suggestions?
P0016 code
- Thread starter FrankV
- Start date
xavierny25
Member
---^--- +1 ... and If the CASE Relearn does not make the P0016 Code go away Permanently and you start getting the Dreaded P1345 Code as well... THIS Link has the Best Procedures to follow if ...God Forbid...the Cam Phaser fails to activate via a Tech2 Commanding it to do so... and it needs to be replaced ...again...to solve this problem:
https://gmtnation.com/forums/threads/how-to-replace-the-cam-phaser-aka-vvt-actuator.14924/
Did you also replace the Timing Chain Tensioner when you had the motor partially apart? These images on my "Flickr-Bucket" will show you what this extra HW looks like when New; Up Close and Personal... mixed in with other Head Removal Images not part of THIS particular job:
https://www.flickr.com/photos/126111508@N07/albums/72157695921930542
https://gmtnation.com/forums/threads/how-to-replace-the-cam-phaser-aka-vvt-actuator.14924/
Did you also replace the Timing Chain Tensioner when you had the motor partially apart? These images on my "Flickr-Bucket" will show you what this extra HW looks like when New; Up Close and Personal... mixed in with other Head Removal Images not part of THIS particular job:
https://www.flickr.com/photos/126111508@N07/albums/72157695921930542
Last edited:
Mooseman
Moderator
Yes cam phaser does activate using a snap-on scanner and yes I changed tensioner and crank and intake cam gear
The timing at idle will move anywhere from 4 degrees to 16 degrees, if I tap the accelerator pedal, as the engine RPM slows , the timing will go down to 4 degrees, then as the engine is idlingit starts to slowly climb up to between 11 and 16 degrees without touching accelerator, which puzzles me
You have not mentioned your sources of information and methodology for conducting this repair... but it is obvious from your answers so far that you did your Homework and you really know what you are talking about. The only other issue that can rear its Ugly Head here and cause the P0016 and P1345 Codes... concerns the Installation of the Harmonic Balancer using the proper New Replacement Friction Washer tucked around the inner HB Flange and then applying 110 Foot Pounds of Force... followed by Painting a Vertical White line that marks the position over the Facing Head of the Bolt... so it can then be tightened an additional 180 Degrees. Doing it this way obviates the need to use a Torque Angle Gauge in those tight quarters... so when the White Line gradually rotates Clockwise and gets matched up Vertically again on the Bolt... You're Done.
But..... Before you Start... There is a real need to Secure the Crankshaft in Place prior to attempting this action via pulling out the Black Plastic Plug in the vertical underside of the Oil Pan and then slip in a 1/2" 15 MM Deep Socket to match it up with one of the Three Torque Converter Bolts after aligning it with the opposite side of that Hole. Then just install a 1/2" Breaker Bar and Brace it in such a manner as to prevent the Crankshaft from Rotating while you take the action needed to make damned sure that the HB Bolt is tightened correctly on the Harmonic Balancer.
It is worth mentioning that even as robust looking as that Old HB Bolt appears to be... The Harmonic Balancer Bolt is a Torque To Yield Version that deserves to be Brand New because like it or not... it WILL get stretched enough NOT to to be able to tighten properly if it gets re-used. If the one you have presently installed is NOT New... then this could explain this entire problem, According to the TSB on this Matter... GM only offers what I mentioned here as the means to stop the HB from slipping and inducing the P0016 and P1345 Codes. Their Last Resort to solve this problem is the ridiculous requirement to Replace The Entire Engine. How absurd is THAT? Here are some excerpted images from my "Flickr-Bucket" for reference on New GM 4.2L Engine Parts:
https://www.flickr.com/photos/126111508@N07/albums/72157671179967478/with/29528230058/
But..... Before you Start... There is a real need to Secure the Crankshaft in Place prior to attempting this action via pulling out the Black Plastic Plug in the vertical underside of the Oil Pan and then slip in a 1/2" 15 MM Deep Socket to match it up with one of the Three Torque Converter Bolts after aligning it with the opposite side of that Hole. Then just install a 1/2" Breaker Bar and Brace it in such a manner as to prevent the Crankshaft from Rotating while you take the action needed to make damned sure that the HB Bolt is tightened correctly on the Harmonic Balancer.
It is worth mentioning that even as robust looking as that Old HB Bolt appears to be... The Harmonic Balancer Bolt is a Torque To Yield Version that deserves to be Brand New because like it or not... it WILL get stretched enough NOT to to be able to tighten properly if it gets re-used. If the one you have presently installed is NOT New... then this could explain this entire problem, According to the TSB on this Matter... GM only offers what I mentioned here as the means to stop the HB from slipping and inducing the P0016 and P1345 Codes. Their Last Resort to solve this problem is the ridiculous requirement to Replace The Entire Engine. How absurd is THAT? Here are some excerpted images from my "Flickr-Bucket" for reference on New GM 4.2L Engine Parts:
https://www.flickr.com/photos/126111508@N07/albums/72157671179967478/with/29528230058/
Last edited:
Ok my source of information on this repair was Google and YouTube, they explain every step very clearly, including the proper way to torque down the harmonic balancer and both cam gears and also the use of the socket through the opening in the rear of the oil pan which I didn’t trust because I did not want to crack the pan so I use a wood wedge after I removed the oil pan and wedged it between the crank and the engine block to stop the crank from turning, which was also the means I used to loosen the harmonic balancer bolt. I have been working on cars on and off since I was a kid now in my 60’s, so I had basic knowledge but this design blew my mind how you have to take the whole front of the car apart for that one small bolt on the oil pickup line, but getting back to matter at hand yes I did put new washer and bolt in harmonic balancer and new bolt in cam phaser gear, I am regretting not getting the original Delphi type phaser and purchased the Dorman type and keep thinking this could be the problem maybe or not putting a new oil pump in all though the pressure reads good, 40 pounds at idle and 60 when accelerating. Also it is not my car, I am helping a friend out and when I opened it up I could see he didn’t change the oil on a regular basis, I flushed the engine with half diesel and half oil but am conserved I am not getting the proper oil flow to the phaser and thinking this is why the p0016 code only triggers when I am coming to a stop with low rpms
Sometimes it is necessary to remove the CPAS and Clean the Screens again AFTER performing the Diesel-Oil Flush as more of the dislodged CRAP from elsewhere inside of the engine can be re-deposited within those Screens. The Oil Pressure Gauge on the Dash Panel is NOT Accurate. You might want to take a look at these two videos... I just posted them here this morning on this exact topic. They will explain what needs to be done to determine the ACTUAL Oil Pressure inside of the Engine and will be definitive in showing any problems with the Gerotor Oil Pump:
https://gmtnation.com/forums/threads/no-oil-pressure-at-idle.4800/post-564587
By the way... As far as the strength of the back of the Crankcase around that Access Port is concerned... The unique aspect of this motor is just how much of the structural "load bearing members" are distributed between the Engine Block, the Crankcase, the Front Timing Cover and the Rear Crankshaft Seal Cover Plate... to sort of create a "Strong Box"effect. This is a quote that also explains just how robust the Aluminum used in the making of the Motor... really is:
"GM used a Premium Aluminum called A356 as the Primary Material for Casting. The Aluminum is very similar to the Aluminum used in Wheels, but is Heat-Treated to Increase Strength. The same Aluminum and Heat-treating were also used for the Cylinder Head."
https://www.topspeed.com/cars/car-n...-engine-gm-s-42-liter-atlas-i-6-ar174949.html
https://gmtnation.com/forums/threads/no-oil-pressure-at-idle.4800/post-564587
By the way... As far as the strength of the back of the Crankcase around that Access Port is concerned... The unique aspect of this motor is just how much of the structural "load bearing members" are distributed between the Engine Block, the Crankcase, the Front Timing Cover and the Rear Crankshaft Seal Cover Plate... to sort of create a "Strong Box"effect. This is a quote that also explains just how robust the Aluminum used in the making of the Motor... really is:
"GM used a Premium Aluminum called A356 as the Primary Material for Casting. The Aluminum is very similar to the Aluminum used in Wheels, but is Heat-Treated to Increase Strength. The same Aluminum and Heat-treating were also used for the Cylinder Head."
https://www.topspeed.com/cars/car-n...-engine-gm-s-42-liter-atlas-i-6-ar174949.html
Last edited:
Thank you for all your input , I will check that pressure with the gauge which I thought I should have done. i do watch many of videos put out by May03. One other thing, do you think you would totally rule out a bad throttle body being that the throttle position sensor is permanently attached to the throttle body, cause I was thinking if the TPS is has a dead spot or is bad if it sends a false reading to the PCM and the PCM asks the VVT solenoid to adjust the timming incorrectly and triggers a correlation code
Probably not... Since The PCM, The Throttle Body, The Accelerator Pedal and if 2005 or later in Age... The MAF/IAT Combo (no MAP) are all intimately connected as a Discreet Circuit; strictly to deal with nothing but Managing Air Flow into the Engine and using the O2 Sensor Readings to figure out how much Fuel to add at any given moment of demand.
The Discreet Circuit for Managing Torque Throughout the Full Wide Performance Range of what is possible with this unique LL8 Engine involves The PCM, The Camshaft Phaser, The CPS, The CPAS and The CKP Sensors to know when the PCM should make variations of 0-25 Degrees of Advance/Retard of the Exhaust Camshaft and accommodate the Power Band.
As Brilliant a design as the Cam Phaser really is... its only Weak Spot centers around the fact that the CPAS Solenoid has INFINITE VARIABILITY in motion as an "Oil Valve" and thus... there is no way for the PCM to know exactly how much Oil is passing In and Out of the Cam Phaser...or whether the CPAS Screens are totally Clogged Up... or Patent and Clean. The symptoms of the Stumbling at Idle and the Sketchy Performance at Higher RPM at Highway Speeds are usually the first clues that the CPAS is probably Clogged Up and/or Leaking Oil through the Electrical Connector and Malfunctioning.
These are the Mechanical Things that can Go Sideways:
(1)The P0016 Code could mean that the In-Dwelling Cam Phaser 0-25 Internal Stopping Lock was accidentally broken off during its installation (...not an uncommon occurrence) and the result will cause this malfunction.
(2) Another cause would be the Incorrect relationship between the ACTUAL position of the Crankshaft versus that of the Exhaust Camshaft if the Lower Timing Cog and the Crankshaft Alignment Pin (...a poor substitute for a REAL Woodruff Key-Slot) are being disturbed by having a Loose Harmonic Balancer.
(3) Of course, the relationship between the Timing Chain and the Marks originally set in place should have the Two Camshaft Locator Teeth covered by Black Links on top and the Crankshaft Cog at the Bottom Right side also showing a Black Link over the Alignment Dot and not prove to be off by even One Tooth.
(4) And also the Two Flats at the Back of the Dual Camshafts should be sitting Level and equally Horizontal back there while the OEM Name of "Delphi" on the Cam Phaser is horizontally even with the top leading edge of the Engine Head when all of these other set-ups have been established.
According to your prior description... you achieved these results properly during re-assembly... so if (2), (3) and (4) can be eliminated...it only remains that (1) Cam Phaser might be The Culprit if the Internal Stop has been damaged or broken off ...or not correctly repaired during its "Re-Manufacture".
The Discreet Circuit for Managing Torque Throughout the Full Wide Performance Range of what is possible with this unique LL8 Engine involves The PCM, The Camshaft Phaser, The CPS, The CPAS and The CKP Sensors to know when the PCM should make variations of 0-25 Degrees of Advance/Retard of the Exhaust Camshaft and accommodate the Power Band.
As Brilliant a design as the Cam Phaser really is... its only Weak Spot centers around the fact that the CPAS Solenoid has INFINITE VARIABILITY in motion as an "Oil Valve" and thus... there is no way for the PCM to know exactly how much Oil is passing In and Out of the Cam Phaser...or whether the CPAS Screens are totally Clogged Up... or Patent and Clean. The symptoms of the Stumbling at Idle and the Sketchy Performance at Higher RPM at Highway Speeds are usually the first clues that the CPAS is probably Clogged Up and/or Leaking Oil through the Electrical Connector and Malfunctioning.
These are the Mechanical Things that can Go Sideways:
(1)The P0016 Code could mean that the In-Dwelling Cam Phaser 0-25 Internal Stopping Lock was accidentally broken off during its installation (...not an uncommon occurrence) and the result will cause this malfunction.
(2) Another cause would be the Incorrect relationship between the ACTUAL position of the Crankshaft versus that of the Exhaust Camshaft if the Lower Timing Cog and the Crankshaft Alignment Pin (...a poor substitute for a REAL Woodruff Key-Slot) are being disturbed by having a Loose Harmonic Balancer.
(3) Of course, the relationship between the Timing Chain and the Marks originally set in place should have the Two Camshaft Locator Teeth covered by Black Links on top and the Crankshaft Cog at the Bottom Right side also showing a Black Link over the Alignment Dot and not prove to be off by even One Tooth.
(4) And also the Two Flats at the Back of the Dual Camshafts should be sitting Level and equally Horizontal back there while the OEM Name of "Delphi" on the Cam Phaser is horizontally even with the top leading edge of the Engine Head when all of these other set-ups have been established.
According to your prior description... you achieved these results properly during re-assembly... so if (2), (3) and (4) can be eliminated...it only remains that (1) Cam Phaser might be The Culprit if the Internal Stop has been damaged or broken off ...or not correctly repaired during its "Re-Manufacture".
Mooseman
Moderator
Depending on if you need to replace the phaser or return it on warranty, Dorman does make new phasers for these engines. I installed one to replace a reman one from ACDelco. The symptoms are similar to yours.
https://gmtnation.com/forums/threads/dorman-now-has-vvt-cam-phaser.14839/
https://gmtnation.com/forums/threads/dorman-now-has-vvt-cam-phaser.14839/
Thanks again, I think I will have to tear it down again and double check everything and this time install a new oil pump while I am at it. It does have 130,000 miles so the pump could be worn, but first I will check the oil pressure with a regular pressure gauge. I will not be happy if I purchased a bad phaser, but that is very possible, but it was brand new, and I blew light compressed air in the inlet hole and it worked properly, so hoping that maybe oil pressure is not strong enough to move phaser and I don’t have to get another one. The timing when accelerating does top out at 25 degrees and like I mentioned it will go down to 4 degrees when rpms come back down to idle, but slowly move back up to 11to16 degrees when idling, so my thoughts are oil pressure is not strong enough to fight the spring pressure and hold it down to the 5 degrees at idle , I believe the timing is supposed to be at idle. One other thing I read one guy on this site doing a timing chain on the same year Trailblazer, 04, he said he set the black links on the timing chain to all the proper marks, then manually turned the engine over, and for each 2 rotations of the crank, (one rotation of the camshaft) the black links would be one tooth off from the marks, so it would take 14 revolutions of the crank to get all of the black links back on all of the marks, this was the same situation I had, I didn’t see anyone answer his question on this, so do you know if this is what is supposed to happen
Last edited:
Mooseman
Moderator
Oil pump failures on these are quite rare. More issues with clogs at the screen but since you had it all open, you did clean it out? Possible that the tube to pipe seal was damaged. We'll see after your oil pressure check.
Yes I installed a new variable valve solenoid so the screens were clean and I removed the exhaust cam front cap and made sure the ports were cleaned out
Yes that is the phaser I used on this vehicle, I seem to like this design better then the original, it seems that it won’t get stuck as easy as the original one would, I just hope I didn’t get a defective one
Oh yes, I took the pick up tube out and cleaned it, also put a new seal in it when I installed it,all good there
Every 7th Link on the GM 4.2L LL8 Timing Chain ...is a Black Link. Since the Two Camshafts Rotate at 1/2 the Speed of the Crankshaft ...from a proper Starting Setting where ALL Three (3) Black Links are lined up with their correct respective markings on each of the Three (3) Sprockets... Beginning with that First Rotation...it will take a total of (14) Clockwise Rotations of the Crankshaft in order to bring all of the Original Three (3) Black Links right back to their Original Positions.
In Post #15 @Mooseman mentions the rare possibility of the Gerotor Pump Failure ...and I can bear out that this CAN happen...if any of the (7) Fasteners holding the Gerotor Oil Pump and Gear Box to the Timing Chain Cover ever come loose. During the Tear Down of my 2004 GM 4,2L LL8... I was unfastening the Gerotor Pump Housing Gear Box... when I reached the Bolt/Screw located near the Oil Pick Up Tube Side... and THAT Screw came out with my Bare Fingers.
At first... I thought, "Perhaps I unbolted this damned thing...and just forgot doing so..." So to double check myself on that possibility... I eyeballed the Threads on the Screw ...and they were completely saturated with Old Engine Oil. To make damned sure that I wasn't Crazy... I also inserted two dry Cotton Swabs...one into the Suspect Hole in the Timing Chain Cover...and the other into the opposing adjacent hole ...to see if perhaps they had simply gotten filled with oil if I had loosened previously loosened those Bolt/Screws. It was impossible to tell if this was caused either by a Crack in the Housing ...or one in the Pump side of the"Clamshell" . Nonetheless... replacing the whole damned thing was the only thing that made any sense.
As you can see from the attached images... the Suspect Hole was FILLED WITH OLD MOTOR OIL and the adjacent one ...was Bone Dry. So the "Moral of this Story: would be to engage with that Gerotor Pump Housing with an abundance of caution... even if like me...you opt for the Later, Updated GM Version/Pump Design by obtaining a NEW ONE ... and perhaps R&R those (7) Bolt-Screws and after using some High Temp Thread Locker on ALL of them... tighten them all down following a Star Pattern to the Factory Torque Spec ...just to be safe:
At first... I thought, "Perhaps I unbolted this damned thing...and just forgot doing so..." So to double check myself on that possibility... I eyeballed the Threads on the Screw ...and they were completely saturated with Old Engine Oil. To make damned sure that I wasn't Crazy... I also inserted two dry Cotton Swabs...one into the Suspect Hole in the Timing Chain Cover...and the other into the opposing adjacent hole ...to see if perhaps they had simply gotten filled with oil if I had loosened previously loosened those Bolt/Screws. It was impossible to tell if this was caused either by a Crack in the Housing ...or one in the Pump side of the"Clamshell" . Nonetheless... replacing the whole damned thing was the only thing that made any sense.
As you can see from the attached images... the Suspect Hole was FILLED WITH OLD MOTOR OIL and the adjacent one ...was Bone Dry. So the "Moral of this Story: would be to engage with that Gerotor Pump Housing with an abundance of caution... even if like me...you opt for the Later, Updated GM Version/Pump Design by obtaining a NEW ONE ... and perhaps R&R those (7) Bolt-Screws and after using some High Temp Thread Locker on ALL of them... tighten them all down following a Star Pattern to the Factory Torque Spec ...just to be safe:
Last edited: