Cybrjaz

I have an '06 Avalanche 5.3L Z71 (4x4) with 168K miles ...

Never had any major issues with it ... just a bunch of little annoying ones (lights on steering wheel not working all the time, passenger side rear door doesn't trigger interior lights, Climate Control system doesn't blow on setting 1 or 2, but does on 3-5, occasionally says that it is in 4H when it's not ... the list goes on) ...

I am the only owner of this truck and I've always used synthetic oil ...

Here's my concern ...

Two days ago I noticed my oil gauge was pegged at 80psi while driving ... it only drops slightly (75-78) at idle ...

It has always run between 40 - 60 psi depending on how slow/fast the vehicle was traveling ...

I'm guessing this means either a bad Oil Pressure Sending Switch (oh so conveniently placed in the top of the block at the back of motor underneath the fuel rails and about 3,000 wires) or a bad gauge ...

NOTE: Three days ago, I came out to my truck having a dead battery .. I jumped it with my jump box, charged the battery , and haven't had any problems since (I know, I know - it's only been three days)


QUSTIONS:

(1) How do I test the gauge? ... Since checking oil pressure means pulling the sensor and if I do that I might as well replace the damn thing ...

(2) Is this really a big deal? I know that low/no oil pressure is a big deal, but I get differring opinions on high oil pressure ...

(3) Assuming it is a bad gauge, how much of a PITA is it going to be to change it out or should I just leave it be?

Thank you in advance for your time and input ...

oldchevy

You can put in a mechanical gauge to see if the pressure really is that high. There was a problem with all gauges in all GM vehicles from 03 to 06. The had bad stepper motors in all 6 of the gauges and they can fail one at a time or several at the same time. This may be your problem so a mechanical gauge can lead you in the right direction.

Cybrjaz

I ran across a test for the gauge ... goes something like this ...



(1) Check the oil level and correct as necessary. Turn the ignition switch on, but do not start the engine.

(2) Disconnect the sensor lead at the sensor. The gauge should read full scale.

(3) Ground the connector. The gauge should read at the bottom of the scale.

(4) If the gauge functions properly, replace the sensor.




I run this test and my guage reads fullscale once the key is turned ... disconnect the sensor lead and the gauge drops down to zero ... After that I didn't bother attempting to ground the sensor lead ...

I'm guessing the gauge is shot ...

kevinkpk

Looking at an electrical schematic (such as it is in Haynes). Power goes to the gauge, the ground side is to the sender unit which is a variable resistor to ground. I'm going to guess the voltage to the guage is 5 volts as that is what most contol systems use. The higher the oil pressure the lower the resistance to ground, thus higher the guage reads. Example, say 5 volts with zero ground resistance is full scale, or 80 psig. At 40 psig, the sender unit is moving 2.5 volts to ground. If you have a volt ohm meter, I'd check the voltage with key on not running at the sender unit. I'd also check resistance at the sender unit, record it. If you can start the car without the sender hooked up, with it running, check the resistance at the sender. No significant change I'd call it sender issue.

Cybrjaz

okay ... so I went awhile with the gauge pegged at 80 ... last week it started bouncing all over the place ... everything that I came across said it was the Oil Pressure Sending Unit ... which by all accounts does absolutely NOTHING but regulate that gauge ... Suffice to say, I would simply leave it but for the fact that driving around with your Oil Pressure readings zero is enough to drive anyone crazy ...

So research showed that the aftermarket versions of this part suck ... and the placement of the sensor in question sucks even worse ...

GM part cost a litte under $50 and it takes a 1 1/16" Deepwell socket to remove ...

The biggest socket you can use is for the 1/2 drive ... 3/4 drives are too thick to fit down in the recesses of the block ...

You can't see anything even if you do remove the plastic intake manifold cover ...

USE GLOVES otherwise your hands will be cut/scratched up while reaching down to get to the part ...

Felt kinda like I was noodling for the damn thing ...

You'll also need a 4" extension bar as the standard 2" is too short but the 6" is too long ...

I didn't want to use a knuckle because I didn't want to tweak the sensor while going in or coming out ...

All in all - slow and steady progress had the part changed out in under 30 minutes ...

The local shop quoted me $140 to replace the part (which included the part) but I just can't get past paying someone to do something that I can and/or should be able to do myself ...

Now the guage is working as it should and all is well ... for now ...