any mechanics?

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any mechanics?

Postby MOSSBERG935 » Wed Feb 04, 2009 4:49 am

my truck is a 2003 Chevrolet Z71 5.3L

twice now on my way home from work (~10degrees outside) half way home (5miles) i noticed my oil pressure dropping. i check the dip stick both times and i have plenty of oil. the oil pressure reads zero.

i replaced my oil sending unit once. the symptoms the first replacement was: the gauge showed i had 80+ lbs. of oil pressure when i normally run around 50 to 60lbs. i replaced the sending unit and it was fixed.

what do you guys think the problem is?
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Postby devildog28 » Sat Feb 07, 2009 11:33 pm

Sounds like it could be an intermittant short in the wiring. A way to check would be to trace the wire and run an ohm test. This would of course require you to crawl under in and trace the wire. :biggrin:
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Postby LaRedneck » Sun Feb 08, 2009 3:39 pm

03 chev? I think to check the codes is turn the key on then off...pump the gas pedal three times "hold it down" then turn the key back ON...see what happens and get back to us.
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Postby MOSSBERG935 » Sun Feb 08, 2009 11:15 pm

the key thing didn't work.....it hasn't thrown a code....from what i understand the sending unit is not connected to the computer in anyway...it is only connected to the dash panel.
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Postby HuntersDad » Mon Feb 09, 2009 12:02 pm

I've worked on alot of GM vehicles and have found them to throw codes without the CEL coming on. Take it to autozone/advance auto and have them run a code test just to make sure.
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Postby devildog28 » Thu Feb 12, 2009 6:12 pm

I think the key thing only works in OB1 pcm's
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Postby KCDuckMaster » Thu Feb 12, 2009 6:29 pm

What is the oil pressure dropping to? When you say your oil pressure is dropping do you mean its going to zero or is it just loosing some pressure?

Also the engine PCM does see the signal from the oil pressure sender. That signal is communicated through the CAN Bus from the Dash Controller to the PCM and other Modules on the truck. If you look at a wiring diagram there will be 2 terminals CAN HI and CAN LO and they will be a twisted pair. Just some FYI
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Postby MOSSBERG935 » Fri Feb 13, 2009 11:29 pm

it was dropping to zero very slowely (about 15 seconds)....
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Postby KCDuckMaster » Sat Feb 14, 2009 10:40 am

Well, I'm thinking its still has to be electrical. If it was mechanical, you would either have too much pressure or you would have zero pressure.

Since you do have pressure usually, that tell me your pump is fine.

So the only other mechanical thing it could be is the pressure regulator. Which if it failed then you might see a low oil pressure but it would not be zero. And since this happens when its cold then that would only help increase the oil pressure.

I would be looking at that pressure sender again or the gauge itself, because a slow drop in pressure on the gauge usually isn't a bad or loose connection or bad wiring.

Another question though, does the oil pressure come back up on its own, without turning the engine off, then restarting it?
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Postby duckslayer82 » Sat Feb 14, 2009 2:15 pm

You are letting the truck sit for a bit before checking the oil correct? If so, sounds electrical to me too. You can also take it to a chevy dealer and have them hook it up. They should be able to find the prob in a matter of seconds then shoot you a price to fix or if you decide to fix it yourself you'll know where to start.

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Postby MOSSBERG935 » Sat Feb 14, 2009 11:18 pm

i replaced the oil sending unit...so far so good....every thing on the old one looked fince, but could have been something wrong with it..who knows.

thanks all
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Postby waterfowlhunter » Sun Feb 15, 2009 7:53 am

my 2001 was doing this and the bypass spring in the oil pump was bad. it eventually caused the engine to go and GM replaced it under warranty. I found out later that the oil pumps were a big issue with the 8.1L engines and there was a bullitin issued. The bad part was that the dealer would not fix it until the engine went.


I hope yours was electrical, it looks like you got it with the new sending unit. :thumbsup:
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Postby blineman » Mon Feb 23, 2009 11:34 am

Some time back (a few years) I had an oil pressure problem like yours , I went to everyplace I could find to corect the problem, spent oddles of cash on this thing. I just changed the oil and filter 250 miles before the crap started. Found out it was the stupid oil FILTER, was doing too good of a job and pluged it self up , changed it and never had a oil pressure problem again. It may have been just a bad filter I dont know.
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Re:

Postby devildog28 » Tue Mar 03, 2009 12:38 am

blineman wrote:Some time back (a few years) I had an oil pressure problem like yours , I went to everyplace I could find to corect the problem, spent oddles of cash on this thing. I just changed the oil and filter 250 miles before the crap started. Found out it was the stupid oil FILTER, was doing too good of a job and pluged it self up , changed it and never had a oil pressure problem again. It may have been just a bad filter I dont know.


Just what filter was that? A K&N?
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Re: any mechanics?

Postby ajmorell » Tue Mar 03, 2009 6:40 am

Probably a FRAM :eek:
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Re: any mechanics?

Postby MOSSBERG935 » Wed Mar 04, 2009 2:19 pm

no i don't use FRAM...i use NAPA Gold or WIX....and the problem is fixed....it was the oil sending unit....been three weeks now with no problems... :thumbsup:
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