Check Gauges and Oil Pressure Drop [Archive] - Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum

: Check Gauges and Oil Pressure Drop


Trailblaze_2002
06-18-2010, 11:48 AM
Ok so i searched and read some threads on here about this problem but after replacing the Oil Pressure Switch the problem still exists. So i changed the Switch today while changing the oil and unhooked the battery since i cleaned the Throttle Body, but i drove around a bit and noticed that when i let off the gas the oil pressure gauge drops to 0 and the Check Gauges Light comes on. I know that the gauge is just a number made up by the PCM but would really like to knows its working in case i do have some problem with it losing oil. It is an 02 with 199,400 miles on it :eek:. It doesn't make any knocking or ticking noises and seems to run fine other than the gauge going to 0. If i push the gas pedal then it goes back up to normal but when i let off it will drop. Any help on this issue is greatly appreciated. I was thinking it could maybe be a short somewhere in the wiring to the Switch but not sure.

Thanks,
Drew

Trailblaze_2002
06-18-2010, 01:20 PM
I just went and got a socket for it and tightened it up also found some oil on the connector from earlier and wiped that off hooked it back up and it seems to be ok. Will get back and let ya know if its fixed later on after i put some more miles on it. :D

bartonmd
06-18-2010, 01:28 PM
What did the test gauge read when you put the $10 mechanical pressure test gauge on it, before replacing anything?

Mike

Trailblaze_2002
06-18-2010, 01:40 PM
What did the test gauge read when you put the $10 mechanical pressure test gauge on it, before replacing anything?

Mike

Didn't put one on it but know the pressure is ok has to be the motor runs great and no leaks anywhere don't burn oil. Changed the oil today and checked it and re-checked it again and again to make sure it was ok. Seems fine actually even better than fine runs like new after the Throttle Body cleaning and shifts good all seems good cept this damn gauge which seems ok now only time will tell. Can i get a Test gauge at an auto parts store or where can i get one.

bartonmd
06-18-2010, 01:56 PM
Didn't put one on it but know the pressure is ok has to be the motor runs great and no leaks anywhere don't burn oil. Changed the oil today and checked it and re-checked it again and again to make sure it was ok. Seems fine actually even better than fine runs like new after the Throttle Body cleaning and shifts good all seems good cept this damn gauge which seems ok now only time will tell. Can i get a Test gauge at an auto parts store or where can i get one.

I got mine from Harbor Freight, but you can get them a lot of places... Parts store may be a bit more money, though...

I had a Taurus that I thought had an oil pressure switch issue, then I replaced the switch and still had the issue... (Turned out mine was sludge that had clogged the pickup) ... No knocking, no funny noises, no nothin'... until I put a gauge on it and found out I had ~1-2psi of oil pressure...

With that mileage, your oil pump could be wearing out and the tolerances aren't as tight as they once were, so not only is it not pumping as well, but your bearings will be getting more worn, and will hold the oil less tightly, and also cause lower oil pressure... At speed, it could be that it pumps enough, but at idle when the pump slows down, it may not be putting out enough any more...

If you start getting the low oil pressure light again, before driving it at all, I'd check the pressure with a test gauge and make sure you're not grenading your engine while trying to troubleshoot your gauge and wiring...

Mike

Trailblaze_2002
06-18-2010, 04:02 PM
Well it hasn't done it again since i cleaned the oil off the connector. Just hope it's the issue gonna get a pressure checker and see just to be safe. As for the oil pump it pumps with the engine so don't think it's the issue but as you said with high miles like this could be possible. I honestly don't think i needed a new switch just needed to clean the oil off of the old one. But the old one's O ring was wore out thus is why it had oil on the connector in the first place. I know it's not the wiring, checked that. Will keep an eye on it and listen closely. As for sludge i can tell you it's not that i have used nothing but Synthetic oil in it and changed it via the OLM. Same for the tranny cept i do 30,000 mile intervals and only use Dex VI. I keep up really good Maintenance on it so i'm sure sludge isn't a problem. Thanks for the ideas will keep them in mind if the problem returns. :thumbsup:

Oh hey could you maybe show me a pic of the gauge you got? I just wanna know what it looks like so i get the right thing.

bartonmd
06-18-2010, 04:25 PM
Well it hasn't done it again since i cleaned the oil off the connector. Just hope it's the issue gonna get a pressure checker and see just to be safe. As for the oil pump it pumps with the engine so don't think it's the issue but as you said with high miles like this could be possible. I honestly don't think i needed a new switch just needed to clean the oil off of the old one. But the old one's O ring was wore out thus is why it had oil on the connector in the first place. I know it's not the wiring, checked that. Will keep an eye on it and listen closely. As for sludge i can tell you it's not that i have used nothing but Synthetic oil in it and changed it via the OLM. Same for the tranny cept i do 30,000 mile intervals and only use Dex VI. I keep up really good Maintenance on it so i'm sure sludge isn't a problem. Thanks for the ideas will keep them in mind if the problem returns. :thumbsup:

Oh hey could you maybe show me a pic of the gauge you got? I just wanna know what it looks like so i get the right thing.

I didn't say you had sludge... Mine was, but it would turn the oil light on at high RPM... The pushrod 3L Ford is pretty bad about that, apparently, and this one had been overheated a lot (purchased it with a dead fan controller and blown head gaskets)...

Because of the type of positive displacement pump that an oil pump is, if it's getting worn out, it will stop sealing as well between the rotor and housing, and and won't pump as much oil, especially at low RPM...

It could also be that the oil pump is fine, but the clearances in your engine (hydrodynamic bearings) have gotten bigger, so even though it's pumping as much oil as it was before, the bearings let is go too easily, which causes low oil pressure...

If the light doesn't come back on, it was probably just the connector... If it does, I'd go ahead and get the pressure tester...

Mine looks like this:
http://www.amazon.com/Engine-Oil-Pressure-Tester/dp/B002TK7CFK
http://ecx.images-amazon.com/images/I/31hbfPt8o7L._SL500_AA300_.jpg

hondok9
07-23-2011, 08:35 PM
Hello to all;
I have a 2002 Trailblazer with 144,457 miles on it.
I recently started a problem that came on rather quickly.
After running my vehicle for a period of time, generally until it warms up (5-10 min) I noticed that when I came to an abrupt stop I would lose oil pressure and My "check guage" light would activate.
I took it to my garage and they said it was a sending unit issue and replaced it.
They did say there was a leak at the sending unit and assured me that the problem was fixed!
After getting it back I experienced the issue the very same day I got it back from the garage.
I took it back and was told "it sounds like to oil pump is going".
When quoted the price I started to look on my own for some other potential problems.
I found that there could be an issue with the guage cluster and read that my best bet was to connect up a conventional guage to confirm that it is actually losing oil ppressure.
I left it and the garage had my vehicle for about 3 weeks and after being called to say it was done, when I went to pick it up I was told that a guage was not connected and that they just put a heavier weight oil (10-40) and an oil additive.
At this point I was irate and left with my vehicle.
I have not noticed any indication of oil pressure after 2 days of driving but, I did check the oil level and found it was down about 1 quart.
I did not check it to see if it was topped off after immediately getting it back from the garage.
I topped of the oil and am going to monitor it.
I bought the vehicle brand new and have always had the oil changed every 3000 miles and used mobile 1 synthetic oil in it.
While driving it today I now have another issue appear and that is rough idling and my service engine light is on.
I forgot to mention that when I got the vehicle back the garage said that the coil pack on cylinder #2 was bad and that was replaced.
I am about at my wits end.
I dont have the money to keep going on fishing expeditions and keep spending money on parts and labor to keep trying various parts to isolate the problem.
I appologize for the long post but, am looking for someone to point me in the right direction since it appears that my garage is not doing that.
Thanks to any and all who can offer advice!

prakoski
10-04-2011, 10:12 AM
I recently started having this issue on my 03 TB, 4.2L, I6. It happened once last week while driving at 40 MPH or so where the check gauges light came on and my oil pressure gauge read 0. It last about 20-30 seconds and then the light went out and the gauge read pressure (45-50 psi).
While driving today, this issue occurred again at slow speed (about 10-20 MPH) when parking at work. Before I jump into changing sensors etc, I would like to check my oil pressure. How can I do this with a pressure gauge?

RayVoy
10-04-2011, 08:47 PM
Your problem sounds like the classic bad oil pressure switch (now called a sensor).

It will take less time to change that to test the pressure.

I say that, because, to connect a pressure tester, you must remove the pressure switch (sender/sensor) and screw in a fitting that will let you connect the tester.

prakoski
10-10-2011, 04:29 PM
THanks Ray. The wiring is disconnected from the sensor so that appears to be the problem. Now to figure out if any local guys carry the wiring from the PCM to the sensor.

RayVoy
10-10-2011, 09:17 PM
Hmmm, that's strange......someone must have broken it changing the filter.

BTW, it is easier to fix if the filter is out of the way.

The old connector is probably still on the original sensor.

avewads
01-23-2013, 06:59 PM
I know this is a very old thread but I am experiencing the same problem in my '03 4.2l. Where, when I stop at a light or stop sign and at low RPM, the gauge goes to zero and then when the RPM's go up the oil gauge goes back to its proper setting.

So My question is this, where is the oil pressure sensor located on on '03 4.2l engine so I can check it, tighten in or replace it?

Thanks - Bob

Tatonka
01-24-2013, 08:46 AM
It's located right above the oil filter, you can't miss it. But that is not your problem. I had the same issue for years and tried to figure out the problem. I just recently read a post here that someone changed their CPAS and that fixed the issue. I have no idea what the CPAS does but it was a $30 part and it's relatively easy to change. When I had my problem I changed the oil pressure switch and it did nothing. I got the same issue within days of changing the pressure switch. Search on here for CPAS and you'll have a better chance at fixing your issue than focusing on the oil pressure switch.