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2005 CTS-V Stealth Gray stock (unmodded and happy this way)
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511 Posts
Discussion Starter #1
Is anyone experiencing this? I'm at my wit's end other than getting a new sensor. My oil pressure gauge reads either ----- (no reading) or 128 or 129 (max reading). This indicates to me the sensor is alternately full closed or full open. There is no variable reading. I can think of only two issues that might cause this. 1. bad sensor or 2. grounding issue. And I know I have those... Anybody have any ideas?
 

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Premium Member
2005 CTS-V
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8,363 Posts
Because the indicated pressure goes from 0-100%-0 the most likely problem is electrical - mechanical issues rarely exhibit that kind of toggle-switch behavior. Having said that, the issue could be the gauge, the oil pressure relief valve, the oil filter, debris in the oil system, or an issue with the oil pump.

See attached.
 

Attachments

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2016 ATS Premium 6-spd MT
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13,973 Posts
Mine's been reading 129 psi for years.


(Note to self: Get off your butt and fix the darn thing!)
 

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2004 CTSV
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590 Posts
Replacing the oil pressure sender is a 10 minute job or less assuming you have a thin wall deep socket. I would do it as a PM job if you haven't already since they are cheap. Get one with a lifetime warranty since you will likely replace it more than once. I've replace 2 so far. First failed at a high continuous reading. The second developed a leak which traveled down the rear of the engine and made me think the rear main seal was leaking.
 

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2016 ATS Premium 6-spd MT
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13,973 Posts
It's behind the Maggie and has to be done by feel. I've got one of those little mirrors that swivels on a stalk. Just need to pop the hood and take a looksee.

Got a modified socket somewhere, just haven't taken the time to do this. Probably misplaced the darn new sender unit I bought, too.
 

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2005 CTS-V Stealth Gray stock (unmodded and happy this way)
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511 Posts
Discussion Starter #9
Thanks everyone. Looks like I have a few things I can check. As far as the oil changes I've done two since buying the car (2 in 6 months at about 3,000 miles each time). Hopefully it's not contamination as the gauge has been faulty since day one.

Darkman: Based upon what you have supplied, two further questions...

1. Can I eliminate the gauge as the problem? I have the multi-function digital gauge. All the others seem to be working fine (except the oil temp for obvious reasons). So can one of the functions fail while the others function normally?

2. In your experience how often would you estimate the relief valves fail? I am planning an oil change in the next few days so I'd consider changing the valve. How easy are they to get? Any parts supplier or dealer only?

Those attached files are awesome by the way. Makes everything so simple to do. Thanks.
 

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2005 CTS-V
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8,363 Posts
Both gauge and relief valve failures are rare. I have not found an online listing for a relief valve, so I assume it's a dealer item.
 

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2005 CTS-V Stealth Gray stock (unmodded and happy this way)
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511 Posts
Discussion Starter #11
Thanks darkman. Maybe I'll bypass that for now and concentrate on the sensor with new ground.

----------

Oops I mean I'll replace both oil pressure and oil temperature sensors.
 

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2005 CTS-V Stealth Gray stock (unmodded and happy this way)
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511 Posts
Discussion Starter #12
Calling darkman!

Or anyone else who has been here... In another thread I was discussing my oil pressure gage and I finally have the replacement switch. I was planning on replacing the switch and replacing the plugs/wires at the same time. Problem is I can't remove the engine cover. I could probably do the wires if I shift around the cover but there is no access to the oil pressure switch. I was reading an on line repair manual that explained "remove the rear half first" but mine is, as I suspect all are, one piece. Is removing the cross engine bay strut bar an option? Or am I looking for more problems?
 

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2004 CTS-V, Black, Borla exhaust
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50 Posts
Re: Calling darkman!

I removed the strut on one then removed the cover. Also had to remove the strut to replace the actual shuts, so no issue removing it. Just torque it down to specs
 

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2005 CTS-V
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8,363 Posts
Re: Calling darkman!

Yep! Remove the strut bar. And unbolt the coil racks from the valve covers and move them out of the way to better access the plugs.
 

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2005 CTS-V Stealth Gray stock (unmodded and happy this way)
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511 Posts
Discussion Starter #15
Re: Calling darkman!

Thanks guys. I was afraid that's the way I'd have to go. I heard about removing the coil racks too but I was hoping to avoid that too. But if it provides better access I'm there. So now... Torque specs on the strut bar? And if I remove it is an alignment necessary? I might do it anyway as I got lifetime alignments when I bought the tires.
 

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2011 CTS-V and 2004 CTS-V
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87 Posts
Speaking of torque, be careful when torquing down the sending unit... I'm sure Darkman can provide the number; if you're not careful you'll strip it quickly. Hard to see what your turning with your deep socket behind the engine. Other than that, super easy job.
 

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2005 CTS-V Stealth Gray stock (unmodded and happy this way)
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511 Posts
Discussion Starter #18
Re: Calling darkman!

Thanks again darkman! :worship: I am ready to dive into this now.

johnathan2169 - - You're correct. I will need torque specs for the sending unit. But in my original thread on the oil pressure gauge it was recommended to me to use the brass fitting instead of the standard aluminum fitting. So I hope that will help some.
 

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2005 CTS-V Stealth Gray stock (unmodded and happy this way)
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511 Posts
Discussion Starter #20
Re: Calling darkman!

Thank you again darkman! I love those pdf's.
 
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