What did you do to your GMT today? [Part II]

Mike534x

Member
Apr 9, 2012
879
That is correct! I'll check the kit to see if the appropriate fitting/adapter is in there. So at minimum, the pressure should be 12 PSI at just idle. I don't know for sure if the pick up tube is blocked, but the oil on the dipstick is relatively clean with the 1500 miles on the oil change done via dealer in Oct (prior to purchasing the truck). No hint of gas in the oil from the smell test either.

I am curious on why the dummy gauge wasn't reading 40 PSI with the switch disconnected, because from past readings the gauge should at the very least give the false reading then?

Cleaning the TB is definitely on the list, I wanted to remove the coil packs and inspect the spark plugs to see if a tune up was ever done, and whether the correct plugs were used. I've got Iridiums on hand, so it'll line up perfectly this weekend when working on her. I'm half tempted to pull the VVT solenoid to inspect the screen, to see if it looks like there's any blockage/gunk clogging it or if the screens are missing like most of them are prone to with age.
 
  • Like
Reactions: Mooseman and mrrsm

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,598
Tampa Bay Area
In order to minimize "Customer Complaints" with an Oiling System NOT using an Analog Gauge... The Factory Default Reading is always ...40 PSI... @MAY03LT has an extensive series of YouTube Videos where he investigates ALL of these Questions with his Tech 2 AND an Analog Oil Pressure Gauge simultaneously ...with very definitive Step-By-Step outcomes to prove what is really going on here. If you check those out, you can compare your results with his and see other important aspects of this issue.
 
Last edited:
  • Like
Reactions: Mike534x

Mike534x

Member
Apr 9, 2012
879
That was precisely where I got the idea from! Which is why I'm wondering if there is a short somewhere, because the gauge still read 0 despite the sensor being disconnected (before the reset). Otherwise, the gauge should default back to "40 PSI". But I am still curious getting a mechanical gauge connected to get a true reading, just to confirm if that is the case or not.
 
  • Like
Reactions: Mooseman

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,598
Tampa Bay Area
You could use the Wiring Diagram that illustrates the Sensor Leads and their destination to check the Continuity of those wires. It is important to know whether or not the Oil Pressure Sensor receives Power either as 12 Volts DC or 5 Volts DC ...or as in the case of most Piezo-Electric Devices...the registry of ANY Internal Oil Pressure acting upon the Zirconium Diaphragm innards manages to generate its OWN Mild Electric Current ultimately carried through the OPS Harness to the PCM.

That signal would then prompt a Pulse Width Modulated signal up to the IPC Oil Pressure Gauge. If you have a Tech 2 ... you can compel the IPC to perform a Gauge Sweep and observe whether or not the Oil Pressure Gauge is performing properly in an almost *Bench Test* manner. If you follow the Alphabetized Listings of the Specific Key Pad Steps to follow in the "IPC" portion of this amazing Document... these Instructions will make this process that much easier to do:
 

Attachments

  • TECH2 Paths.pdf
    490.2 KB · Views: 0
Last edited:

xavierny25

Member
Mar 16, 2014
6,323
Staten Island, N.Y
Yesterday...Cleaned the throttle body and maf sensor. Installed a cleaned and treated green air filter. :Banghead:I'm having issues with a code p0017 and I have to get it fixed before I have to go in for the annual state inspection. :coffee:
20240210_095926.jpg
 

Mike534x

Member
Apr 9, 2012
879
Managed to get some work done on the Trailblazer this weekend. @Mooseman and @mrrsm oil pressure is registering roughly 14-15 PSI at idle. Revving her to 3k yielded 72-73. So it could be an idle issue maybe, waiting on a new VVT solenoid to get here. Otherwise, no further warnings popped onto the dash.

So after doing that, I took care of chopping off the old links, and replacing those. Sway bar bushings were shot, but I'll do those another time. Temps were starting to drop just as I finished. Of course, not every job is "finished". After being satisfied with the oil pressure readings/the less clunky rear it was time to grab dinner. Got home, and pulled into the driveway and kept smelling something...familiar followed by a "groan". Oh no....please don't be the power steering line again. Yep. The crap clamp allowed the UPPER steel line to pop free of the rubber hose.

Dremel came out, chopped off a little bit of the line, inserted a 3/8" barb fitting, and slipped on a few 3/8" worm gear clamps and topped it back off. Before/After pics attached. Should be the last thing I have to touch PS line wise *knocks on wood*.
 

Attachments

  • 20240213_180705.jpg
    20240213_180705.jpg
    605.9 KB · Views: 5
  • 20240213_184531.jpg
    20240213_184531.jpg
    531.7 KB · Views: 5

mrrsm

Lifetime VIP Donor
Supporting Donor
Member
Oct 22, 2015
7,598
Tampa Bay Area
Re: Post #1,125 for @xavierny25 ...FWIW

If you get the chance to do Testing of the Crankshaft to Camshaft Correlation using any Oscilloscope.... This Information will prove invaluable in Diagnosing the P0017 Code:

Known Good Wave Form of a Crankshaft to Camshaft Comparison...with an explanation:
KNOWNGOODWAVEFORM.jpg
But THIS is What a a Known BAD Wave Form looks like for the Crankshaft vs, Camshaft :
KNOWNBADWAVEFORMP0017.jpg
More information can be found via Post #23 in this Link:

 
  • Like
Reactions: xavierny25

Mike534x

Member
Apr 9, 2012
879
Time to track down a short somewhere in the Envoy. Moved it out of the garage yesterday morning with no issues, got into this afternoon to take it for gas/errands and it was completely dead. Ugh...alright, jumped it, and it started it up no problems. Took it for a drive, got home, shut it off and it restarted with no problems. Hooked up the battery tender, and the display is showing the capacity was at 30%.

Hoping to get time this weekend to look at it, its so sporadic that I can't narrow down where its happening. Everything was fine last year with the cold temps we had, and I didn't have this problem. Oddly enough, the gauge cluster stops working partially whenever the battery is disconnected/dead. As in, I'll a working RPM and MPH needle, but gas, temp, voltage, and oil pressure will all read 0/off. ABS, Airbag, and brake light will be illuminated and the "PRND" selector will be lit up and not show the little selector box over what gear the shifter is in. (requires disconnecting the battery a few times before it starts working again). I installed my spare new megafuse earlier, as a precaution that maybe the one in there was the issue.

So my suspicions are either, the cluster has a parasitic draw, or there is a minor fault somewhere causing my gremlins. Wiring harness running alongside the middle half of the center console is pinched/has a minor break somewhere (it was removed by a shop when they replaced the gear shifter), or less likely (and hopefully not) culprit is the BCM....or I've got a module somewhere in the truck that's not shutting off like its supposed to.
 
  • Like
Reactions: Matt and Mooseman

Forum Statistics

Threads
23,236
Posts
637,132
Members
18,404
Latest member
Zoie

Members Online

No members online now.