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2005 Escalade 6.0
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7 Posts
Discussion Starter · #1 ·
Dose someone know the voltage output of the oil pressure sensor?
I have escalade 2005 with 6.0L LQ9 Vortec V8 345 hp motor in and I'm getting sometimes low oil pressure on the car. I measured the output on the sensor and it is measuring from 0,75V in idle to 1,18V on 3500 rpm. And I was wondering what is normal voltage and how dose that translate to pressure.
One year ago I changed out the oil pump, oil pick up and more. Since that I have been getting this error on the sensor mainly when I'm driving uphill for 2-3 minutes.
579426
 

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Administrator
2002 F55 STS, 2014 Explorer XLT, F-150s
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74,575 Posts
General gauge information for background - You would need the sender electrical resistance specs from the GM/Cadillac service manual. If the vehicle has a gauge that actually moves a needle in response to engine rpm/pressure changes then the supply voltage is a constant and the voltage to the gauge is a variable, determined by the changing resistance of the sending unit. The "gauge" is actually a calibrated voltmeter.

A low oi pressure warning when going uphill sounds like there's a pickup tube leak near the normal full oil level line - tilt the engine, air enters the oil pickup, foaming begins, pressure drops. Just for grins, overfill the pan by a quart or so and see if the pressure stays up.
 

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2006 Cadillac Escalade
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39 Posts
Not sure if this has anything to do with your problem but i picked up some parts from a guy who had a wrecked 2004...he told me he uses the LQ9 in a lot of cars he builds and that a common problem with them is the o-ring on the oil pick up tube...he said it’s a $7 o-ring and he’s replaced a bunch of them...maybe this will help
 

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2005 Escalade 6.0
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7 Posts
Discussion Starter · #4 ·
Not sure if this has anything to do with your problem but i picked up some parts from a guy who had a wrecked 2004...he told me he uses the LQ9 in a lot of cars he builds and that a common problem with them is the o-ring on the oil pick up tube...he said it’s a $7 o-ring and he’s replaced a bunch of them...maybe this will help
I replaced the oil pump, oil pickup tube and o-rings around 1 year ago.
 

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2002 F55 STS, 2014 Explorer XLT, F-150s
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74,575 Posts
That's where we're going - something may have gone wrong with your repair.
 

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2005 Escalade 6.0
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7 Posts
Discussion Starter · #6 ·
That's where we're going - something may have gone wrong with your repair.
There is also one thing more that is giving me hard time. The pressure gauge in the dashboard is moving all over the whole gauge, can be 20, nest time when I start the car 80, sometimes when I'm driving for long hours (4-6) then it starts in 20 and in the end of trip is above 80,moving slowly upwards. The voltage meter is often in 19V+ and very often at max of the gauge, but in real when I measure it is around 14V with engine running.

So I was wondering can the pressure sensor give out some fals signals and the pressure gauge in the dashboard is not picking it up? Or do you still think it is a mechanical problem and I need to take the bottom of the engine down to inspect the o-ring and pick up tube?
 

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2011 CTS4 Coupe, 2014 ELR, 2018 XT5 AWD
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911 Posts
I think your problem is electrical not mechanical.
The oil pressure can be low or high depending on the problem sure.
But there is no way the alternator is outputting 19+ volts without major codes and lots of other issues. Check the connections to the cluster and the main cluster ground. Look for grounds on the IP supports and by the base of the A pillars.
My bet is on a ground problem. It could be a bad cluster.
 

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2002 F55 STS, 2014 Explorer XLT, F-150s
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74,575 Posts
Yep - you have major system voltage problems.

Several gauges - oil pressure and coolant temperature for example - depend on fairly steady vehicle system voltages of 12.5 - 14.2 to be somewhat accurate. If system voltage goes above the high spec the gauges read higher; voltage goes below some 12V spec, gauges read lower.

As far as true accuracy goes, nothing beats the old mechanical (capillary tube) gauges. The only electricity going to them was lighting.
 

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Premium Member
2004 Escalade 6.0
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1,227 Posts
Since our Escalades are know for getting bad stepper motors on the gauges I would first read the voltage with a voltmeter and compare with the gauge reading. You can get them cheap on eBay and change them using YouTube videos or send the cluster in for a quick repair. This place can even change your cluster lamps, the also fail often, with colored LEDs. Same day service.

 

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2004 ESV
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908 Posts
You can verify the voltage output by getting a cheap accessory outlet voltage meter. Battery should be a little over 12V when car is off, and just over 14V with vehicle running and alternator charging properly. Something like this;


I know you aren't in the US, but you should be able to find something similar locally.

You could have stepper motor issues in the gauge cluster, which is why the gauge dials are bouncing all over the place. This is a very common issue.

Oil pressure sensor is also very failure prone. Gauge usually fails either reading a constant 0 or 80. Sensor is on the back of the intake, and is removed by feel. If I ever need to replace mine, I'll probably pull the intake at the same time. I know the gaskets are original and the car is 16 years old. I'm sure they aren't in the best shape. It would also make it super easy to replace the sensor.
 

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2005 Escalade 6.0
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7 Posts
Discussion Starter · #11 ·
This is the voltage on the system. But when I took this the voltage gauge in the dashboard was in 19+ Volts.
579471


Dose someone know what are the output voltage on the pressure sensor supposed to be? And how dose that translate to pressure. 1V = ???PSI
 

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2002 F55 STS, 2014 Explorer XLT, F-150s
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74,575 Posts
Your graph of battery voltage (engine off) and system voltage (engine running) as well as start indication of voltage droop is textbook-perfect.

So you have indication or sensor problems.
 

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2005 Escalade 6.0
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7 Posts
Discussion Starter · #14 ·
I revived new oil pressure sensor and put it in. Then I get right away low oil pressure alarm when I start the car. Sensor voltage is about 0,6V. The engine is not making any sounds like the oil pressure is low. So what can then be wrong?
 

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2011 CTS4 Coupe, 2014 ELR, 2018 XT5 AWD
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911 Posts
it could be loose terminals in the connector to the oil pressure sensor or a broken wire leading to that connector. They may have been the intermittent problem you were having and have now totally failed because you disturbed them.
 

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2002 F55 STS, 2014 Explorer XLT, F-150s
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74,575 Posts
Post #2. You need to graph the sending unit resistance vs. pressure, then calculate the gauge indication vs. voltage.
 

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2005 Escalade 6.0
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7 Posts
Discussion Starter · #17 ·
This is getting strange now. I took the new sensor out to see if I damage it, but no visible damage. I changed oil and filter at the same time and now I'm getting low oil pressure when the car is in idle. When it gets above around 1500 rpm then the oil pressure alarm disappear.
Submariner409 do you know where I can get a graph or information about sensor V vs pressure?
 
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