Oil pressure light on, pressure ok

[Intragration]

Here's a new one for me. This is one of my folks' vehicles, not GMT400, but 2007 Trailblazer 4.2 with 130k miles. Oil light comes on, but the oil level is fine and pressure per the gauge is around 40, which is normal for this engine. It's not nearby, so I'm not able to go look at it right now. Any thoughts? My current guess is bad idiot light sending unit.

 

[95burban]

Bad sending unit or the screen under it is stopped up. Happened to me on my 5.3

 

[skylark]

Here's a new one for me. This is one of my folks' vehicles, not GMT400, but 2007 Trailblazer 4.2 with 130k miles. Oil light comes on, but the oil level is fine and pressure per the gauge is around 40, which is normal for this engine. It's not nearby, so I'm not able to go look at it right now. Any thoughts? My current guess is bad idiot light sending unit.

Eh, its a trailblazer. Dash lights are a way of life.

 

[Schurkey]

Funny thing about the Trailblazer 4.2L inline six popper.

THERE IS NO SENDING UNIT/SENSOR FOR THE OIL PRESSURE GAUGE. The dash gauge is controlled by the computer, THE COMPUTER LIES. The computer spins the oil pressure gauge needle to somewhere that looks good, while actually having NO IDEA what the oil pressure actually is. This is GM deceitfulness in action. They give the consumer/operator a "gauge" that in reality is connected to nothing more than wishful thinking.

There is an oil pressure switch, that signals the computer that there is some minimal oil pressure. Like perhaps 3--5--7 psi.

So if the oil pressure light is on...Good luck. Maybe the oil filter collapsed, maybe there's a wiring short to ground in the switch wire.

Maybe the engine is cooked. Point is, since the oil pressure gauge reading is a TOTAL FABRICATION, having the oil light on probably means "something" needs IMMEDIATE attention.

Hard to tell until you remove the switch and install a "genuine" pressure gauge. (Careful...almost certainly Metric threads.)

I have been told--but not confirmed--that the computer lies about the oil pressure because that engine was designed to have unusually-low oil pressure, and they didn't want a bunch of owners coming into the service department crying about warranty-work due to "low" oil pressure that in fact is normal for that engine.

My '03 Trailblazer has 270K miles on it, and I've never checked true oil pressure.

 

[someotherguy]

Funny thing about the Trailblazer 4.2L inline six popper.

THERE IS NO SENDING UNIT/SENSOR FOR THE OIL PRESSURE GAUGE. The dash gauge is controlled by the computer, THE COMPUTER LIES. The computer spins the oil pressure gauge needle to somewhere that looks good, while actually having NO IDEA what the oil pressure actually is. This is GM deceitfulness in action. They give the consumer/operator a "gauge" that in reality is connected to nothing more than wishful thinking.

There is an oil pressure switch, that signals the computer that there is some minimal oil pressure. Like perhaps 3--5--7 psi.

So if the oil pressure light is on...Good luck. Maybe the oil filter collapsed, maybe there's a wiring short to ground in the switch wire.

Maybe the engine is cooked. Point is, since the oil pressure gauge reading is a TOTAL FABRICATION, having the oil light on probably means "something" needs IMMEDIATE attention.

Hard to tell until you remove the switch and install a "genuine" pressure gauge. (Careful...almost certainly Metric threads.)

I have been told--but not confirmed--that the computer lies about the oil pressure because that engine was designed to have unusually-low oil pressure, and they didn't want a bunch of owners coming into the service department crying about warranty-work due to "low" oil pressure that in fact is normal for that engine.

My '03 Trailblazer has 270K miles on it, and I've never checked true oil pressure.

I wonder.. the Colorado and Trailblazer seem to have a lot in common; does the H3 suffer from some of this mess? My wife likes them but so far I've avoided entertaining the subject because they don't seem durable, to me. Maybe I'm wrong? The only one I see as even being an option is the Alpha with the 5.3, and people want too much for 'em.

Richard

 

[Schurkey]

I don't know.

My suspicion is that any of the Atlas engines are the same as far as oil-pressure-sensing--5 or 6 cylinder. Did they make a 4-cylinder version? I once heard that they did, but not from a reliable source.

 

[Intragration]

I don't know, I was aware of the 6- and 5-cylinders, never heard of a 4. It's my opinion that overall, the 6-cylinder is a pretty excellent engine. It's about the latest vehicle I've experienced that still feels like a REAL vehicle, rather than an alien spacecraft. Anyway, this was my old man's truck with the problem, I have an identical one, but his had the oil light. I was busy working at the time and I told him to maybe hold off driving it, but he did anyway, the light went off, and hasn't had a problem since. Not the way I personally would have handled it, but it worked out alright for him. Thanks to all for chiming in.

 

[Dropped88]

They made 5 versions of the atlas engine.

2.8 & 2.9 4.cylinder.
3.5 & 3.7 5 cylinder.
And the 4.2 6 cylinder.

Not saying this is your issue but I've replaced a many of the oil pressure switches because they are junk. But have never seen an issue of low oil pressure in one that's been took care of.

But lack of maintenance eats the chains up in them and then that metal goes through the engine taking out the bearings.