3.8 oil sensor problem

[goldsmith]

OK so here is another one about a 3.8. its a 94 olds 88 royale automatic that my wife drives (165K). it had been giving the trouble message "low oil pressure stop engine" sometimes but not consistently so i took it to autozone for a free scan. the guy said the 94 is sort of a transitional model that is cranky to read because they were switching to the newer scan system and he couldn't pull the code that would have confirmed or clarified the problem. nevertheless, he said this was a common problem that is typically caused by a faulty sender, so i bought one. A mechanic from the shop around the corner from the parts store was there and said these senders are notorious for failing and leaking.I found that the old one had burst at the seal around the inner diaphragm and was indeed leaking. when started i got a message right away "oil pressure 124 psi", then "oil pres sender prob". i took it off and cleaned the connection with brake fluid spray and air and tried it again- a couple of times. then i took it back and swapped it for another one and went through the same process with the same result. i disconnected the battery while replacing it this time hoping that if it was a reset problem that might do it. Nah. The part is the right one for a system with idiot lights (we qualify) rather than gauges and fits the connector precisely. The connector is probably a bit oily inside since it has been leaked on awhile but i don't think thats it. I did see through the oil filler that there is a good pool of oil in the top. surely i didn't get 2 bad senders brand new- did I?

[DanD]

No I don’t think that you bought two defective pressure-sending units, you likely have the wrong one.
Sometimes the after market suppliers will have what their listings say is the proper one, it’ll look and fit but electrically it’s different. I know you’ve checked with Autozone and it should be the proper unit for an oil light system, but the way I read your post you also have a driver information center. Which would make the sending unit more then just an off on switch but a variable resistor as well.
I would go to the dealer with your VIN# and order one from them, if that doesn’t fix it then I’ll try and go through the test procedure with you.
Dan.

[goldsmith]

You were right about the wrong sensor. i talked to the dealer about the parts (with the vin in hand) and found that the one i needed would more appropriately be classified as the one for gages rather than lights. After all, as you pointed out, the message center gets a gaged value for the pressure in this set up. i should have reasoned this out before i did- though i didn't think about it when first buying the part (the old one fell apart when I removed it) it is noticeable when seeing the right part that it is physically closer to the one i removed. The gaged sender is longer by 3/4" or so which makes sense because it has to allow travel through a range rather than just contact off and on. The misunderstanding was whether it was gaged or lit only, and while there is no permanently mounted gage sitting in the dash the MC achieves the same function interactively or when there is a problem. Autozone let me swap for the right one and we're rolling again with about 65 psi. Thank you for lending your experience.

[DanD]

Glad to hear you’ve got it sorted out and thanks for posting the fix.
If you need anything else don’t be afraid to ask and maybe tell your friends about the site.
Dan.

[Tom Greenleaf]

In our day of the computer once incorrect info gets in a parts store's system it's hard to get it out!! New car dealers seem to do well at being accurate. Now a days having your VIN can really help. Also - many cars say the date of manufacture on the driver's door jam and that can help. The car makers do change things mid year. I try to bring old parts to my favorite local store and match them up.