JayBirdWs6

iTrader: (1)

Driving home yesterday I had the AC on auto on the highway and got an alert and saw my oil temp was near 300 and thn it went away for a few seconds and came back so I turned the AC off to see what would happen and the temps went back down to 230-240.

What gives?

Naf

iTrader: (1)

Do you have an oil cooler on your car?

There also might be a fault in your sensor...

Lastly, when was the last time you washed your radiator and engine?

JayBirdWs6

iTrader: (1)

No oil cooler (any info on this possibly?) and I've read about the sensors but havent really came across anything understanding.

It's been awhile since I washed my engine bay area. Would cleaning the engine cause this problem?

Stone17

iTrader: (3)

It a ground issue.

Read.

http://www.cadillacfaq.com/faq/answers/oilguage.html

JayBirdWs6

iTrader: (1)

Software update so I need to contact a dealer? Am I reading that right

Stone17

iTrader: (3)

Yes, I want to do it but never got around to it.

Alot of guys saying adding a star washer on this ground will help (See attached picture). Did nothing for my car.

DarkCharisma

Star washer helped a bit for me, but what fixed the problem was running some 14 gauge wire from the ground on the sensor to the bolt under the hood strut.

JayBirdWs6

iTrader: (1)

Where is the sensor?

Stone17

iTrader: (3)

http://www.cadillacforums.com/forums...-oil-temp.html

demang

iTrader: (3)

I had to do the same as dark did. Now no problems at all.

JayBirdWs6

iTrader: (1)

Is this sensor easy to get too?

DarkCharisma

Really easy. It sticks out the passenger side of your oil pan. I found a schematic online to figure out which wire was the ground, clipped it, ran my new wire up around the battery to the bolt under the hood strut, and voila--fixed.

odthetruth

iTrader: (4)

Ground. Test em with multimeter... wirebrush it all up, add star washer, and test again. Heavymetals had a fix for this a long while back. Seems to only have issues with 04-05.

heavymetals

iTrader: (3)

Actually it is a problem with all models.

Aluminum is a **** ground.

The real method would be to measure the voltage drop across the grounds and see which one has the highest voltage across it.

The bolt beneath the hood strut is the biggest culprit (main ground), however, there is the ground on the frame near the alternator and the ones on the rear of the heads, plus the one by the starter motor.

There is also a ground on the drivers side underneath the carpet on the side next to the radio, which is for the dash.

The temp sensor ground reference is from there if I am not mistaken.

The how to:

Using a DVM, connect the negative lead to the battery terminal.
Turn everything on, A/C, lights, radio.
Measure the voltage on the bolt head that is securing the ground terminal.
You want to see less then 25 mv.
If more then that, remove the bolt, wire brush all contact areas to the bolt, terminal and frame.
Add a star washer between the bolt and the terminal, not the terminal and frame.
Use a contact cleaner to clean the threads of the bolt and the mate.

JayBirdWs6

iTrader: (1)

Sounds like a headache.

DarkCharisma

FWIW I re-did all the grounds (with the exception of the one under the driver's side carpet) and they mitigated the problem, but didn't resolve the mis-reporting.

The new ground wire took me literally 10 minutes and has 100% solved the issue.

JayBirdWs6

iTrader: (1)

And thats the 14g from the sensor to the bolt? I've had this car for 4 yrs and this is the first time it happened to me. It kind of freaked me out.

heavymetals

iTrader: (3)

The oil temp is read by the dash then transmitted by classII to the PCM.

Same as the C5 vette.

There is more then 1 way to skin a cat.

A ground from the sensor to the battery negative is optimum.

demang

iTrader: (3)

Heavymetals do you have a diagram of where all those grounds are? I have a 05 if that makes a difference.

heavymetals

iTrader: (3)

The bolt beneath the hood strut is the biggest culprit (main ground), however, there is the ground on the frame near the alternator and the ones on the rear of the heads, plus the one by the starter motor.

There is also a ground on the drivers side underneath the carpet on the side next to the radio, which is for the dash.

They are all pretty obvious except the ones behind the heads, but even those are obvious once you locate the bolts.

The one near the starter motor is hidden by the headers.