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Damn! High Oil Temp and alarms? Here is a fix for it

151K views 211 replies 58 participants last post by  matt2thepoint 
#1 ·
I know that many have had problems with their Oil Temps reading incorrectly.... Mine has been acting up lately, and after the 3rd dealer visit, it still went off on me today on the freeway. It seems to stay ok until warmed up (approx 30 mins) then jumps up to around 240-250 then if I slow down/stop, or Turn on the A/C it Jumps up to 300 and Ding Ding... SOOOO ANNOYING! Its weird because it seems to be Steady, but high, until i come to a stop, or turn on A/C, The dealer has done the Ground Fix, 2 times at one dealer, and 1 time at another... I got off the phone with them and want me to bring it back on Monday. Seems like my car is at the dealer more than at my house :crybaby:
Anyone Ever Resolve this Issue?? Anyone have the same problems when turning on their A/C?? I would just ignore it, if it wasnt for that stupid Chiming Sound going off!
 
#117 ·
This was a consistent problem for me. 300+ oil temps having no correlation to driving style or outside temps, high oil temp alarm 'Bonging' all the time. I noticed the strange relationship with various electric accessories especially the sunroof. I thought it screamed of a ground loop issue. So I removed the ground at the Pass side strut tower, found the metal fully painted including ID of the threads. Pathetic GM QC... Anyway, scratchy scratchy until it was shinny and the problem is gone for good. For good measure, you should clean up the lug face while you're there is case there is some corrosion. If you want to go crazy, a star washer between the lug and the sheet metal with some 'No-Ox' Electrical Grease would be a good idea, but I didn't bother.

cheers,
mh-
 
#119 ·
Well I am getting to join the club! I did the hood prop ground before my 850 mile trip to PA and never got one ding and the temp hovered around 220. Fast forward to the return trip and it is bonging again! Although I couldn't be happier because the initial "fix" took care of my LC-1 Wideband problems for which I was about to "fix" with a new O2 sensor.

Monday I will check out all my grounds and install my catch can I got for Christmas, we shall see.
 
#122 ·
On a thread related note I spent the good part of 3 (back crunching) hours today locating and cleaning grounds. Preliminary results are good but I will wait a week or two before I say yes for sure and upload some more pics.
 
#123 ·
UPDATE:
Spent about 3 hours the other day and finally got these high temps under control! I still can make them fluctuate with turning on/off accessories but only by a few degrees and not 20 like before.

I ended up adding star washers to the following grounds as well as sanding the lug and area the lug attached to. (didn't sand the heads just cleaned them)

Drivers side head rear.



Passenger side head (both rear not pictured and the side facing the fender/battery pictured)



The ground below the underhood fuse box.

 
#125 ·
I had to Google ASIC (Application Specific Integrated Circuit) and I still don't know what the heck it is! :) I can share in the head banging though as these damn cars and their electrical gremlins can be frustrating. Although it wasn't all for not as I was able to clean up some wiring and route the evap and fuel line a bit cleaner and out of the way...
 
#126 ·
What a great tribute to the Forums! Thank you to all for this information, i will be implementing it soon...I'm curious has anyone noticed that on a cold cold day, (key on, no start) the oil temp can be quite a bit below the actual or forcasted ambient temp? I wonder if this is related or just a weird attribute of oil? I'm in Texas, so I have only seen it on a rare morning here...
 
#127 ·
I'd say its the correct temperature in that scenario. The engine would hold the cold from the night before and even though the ambient was now warmer it would read colder.

The grounding offset issues take some driving time to show themselves.
 
#130 ·
#131 ·
Sweet thanks Tony. My temps are still going off and I am to the point of replacing the sensor and/or grounding it better. I'll check out the connector though.


EDIT/ Which connector of yours was loose? The level/temp sensor plug or the starter connector? (I know my starter connector looks scary so I'm not sure I wanna go plugging and unplugging up in there! :) Brittle old plastic might not like it.
 
#132 ·
On the starter, right above the big wire you bolt down. The clip was broken and I just slid it back in. Only reason I even saw it was cuz the tranny/cats were out of the way.
 
#133 ·
Thanks. I will take a look at it when I get a minute to get underneath her. Thats what she said. :)
 
#134 ·
Well, I can't explain this one... I had the high oil temp gong alarm for the last two years. It was getting worse and would typically go off 10 times during a long trip...even when it is cold out. Definately worse in warmer weather. I cleaned up the ground on the fender well but it did not fix the problem. Never got to cleaning the back of the head or other grounds...

My motor mounts were completly shot and totally seperated. You could spin the top of the mount inside of the bottom larger portion of the mount. I replaced with the new Creative Steel mounts. Guess what, no more overheating oil alarm. I have been driving now for 3 months in cold and warm weather and the oil temp never goes above the 225 area. I can not answer what could have fixed this? The only thing I did was remove the negative battery cable during the install due to the starter being so tight to the mount & swaping in the new mount.

All that I know is this... Something I did during the motor mount upgrade fixed my oil temp alarm issue... I don't believe there is any continuity through the motor mounts so I am pretty much stumped...But very happy...

Dave
 
#135 ·
FINALLY FIXED!!!

I have had this finally taken care of for about a month now and its consistently in the 90's so I know I am good to go. Just ended up running another ground wire from the stupid sensor and that took care of it! (Temps don't exceed 224* and no combination of windows/ac/etc will cause it to raise).

 
#136 ·
Fluctuating oil temp

Today I was driving in some good old Texas heat and my oil temp warning indicator beeped at me. I checked the oil temp and it read 295. I got really worried and coasted for a little but and the temp dropped to 240. I decided to try and make it home, during which the temp fluctuated around 250-270, spiking once more to the 280-290 range.

I never had this issue before my header and cam install in 6000 miles of driving. I driven less than 1000 miles on with the new setup so far. Mods are B&B headers, SNL cam (with supporting hw), intake, modified exhaust and tune. I currently do not have a 160 thermostat or oil cooler.

Anyone have a similar issue after mods? Trying to figure out what I need to do. I'm guessing oil cooler?
 
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#138 ·
Need Help...

Does anyone know if the oil level / temp sensor is one combination sensor? I have cleaned the grounds on the back of the head, main battery ground, replaced the oil sensor in the oil pan and added a jumper from the negative to the frame. Seems to work better for a while but I am now getting the alarm again. Turning on / off headlights and air conditioning causes the oil temperature to jump 50 degrees. I seem to be all out of options and and really sick of this alarm for over two years now. I wanted to make sure I replaced and added the jumper to the correct sensor.

Any help is appreciated.

Dave
 
#139 ·
Yeah it's the same sensor.
 
#141 ·
Thanks for the quick reply... I just read this entire thread again and will add the star washers to the grounds. Also, you may have something with the sensor plug. When I replaced the motor mounts the problem went away for a while. I probably banged against this plug and shook it up a little... My ground jumper is directly outside of the plug but if the plug is bad internally, none of these fixes work.

I am going out with the volt meter now and will add the washers first. Hope it is not the plug as it looks like something hard to find...

Thanks again - Dave
 
#143 ·
Re: Fluctuating oil temp

It is not the ground for the temp sensor that is affected, but the ground reference.

It makes sense if you know anything about low level signal testing and telemetry.

This problem is particularly found in single ended measurements vs differential (no ground reference).

(I happen to be a telemetry "expert" and I got paid BIG BUCKS to solve problems like this before I retired).
 
#144 · (Edited by Moderator)
Re: Fluctuating oil temp

It is not the ground for the temp sensor that is affected, but the ground reference that the PCM uses.

It makes sense if you know anything about low level signal testing and telemetry.

This problem is particularly found in single ended measurements vs differential (no ground reference).

(I happen to be a telemetry "expert" and I got paid BIG BUCKS to solve problems like this before I retired).
I'm sorry...but you are incorrect. A 2005 CTS-V does NOT send the oil temp signal to the ECM. It goes directly to the instrument cluster. Now, a V6 CTS does indeed send that signal to the ECM. But not the LS6. The engineers did not want to see the ECM reducing performance of the LS6 due to elevated oil temps. It's considered a performance vehicle and they left that up to the driver to deal with...not the ECM. The ECM does indeed see oil pressure and oil level in the LS6...but the oil temp is a gauge only.

GM did finally come out with a repair they consider a fix. Please note where they have you fasten the new ground. This is a major vehicle ground used by the cluster, among others.







Subject: Engine Oil Temperature Reads High Or Improper Display Of Warning Message - keywords DIC display gauge IPC #PIC4508A - (10/30/2007)



Models: 2004- 2005 Cadillac CTS-V




--------------------------------------------------------------------------------

This PI was superseded to update model years. Please discard PIC4508.


--------------------------------------------------------------------------------

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
Some customers may comment the engine oil temperature rises very quickly and remains high when they are not driving on long hills or performing aggressive maneuvers. In some cases the Oil Temperature Warning Message is displayed.

Recommendation/Instructions:
If the Engine Oil Temperature Indicator is always on, follow Engine Oil Temperature Indicator Always On (5.7L) Document ID# 1541697. If the oil temperature seems to rise quickly and remain high, install a redundant ground for the Engine Oil Level/ Temperature Sensor to the Instrument Panel Cluster ground G200 using the following instructions:

Splice a new length of .35 AWG wire into circuit 1550 (BK) near the Engine Oil Level/ Temperature using procedures in Splicing Copper Wire Using Splice Clips Document ID# 303646.
Run the wire under the Engine Harness protective sheath following the harness over to, and through the Wiring Harness Pass-through Grommet into the passenger compartment on the driver side.
Attach the end of the redundant ground wire to G200 behind the left kick pad using suitable eyelet terminal.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
 
#145 ·
Re: Fluctuating oil temp

"install a redundant ground for the Engine Oil Level/ Temperature Sensor to the Instrument Panel Cluster ground G200"

"Redundant ground"

I am right, BAD GROUNDING causes a voltage offset.

I erred on what part of the sensor goes to the PCM (temp does not, level does).

The main battery ground is the biggest culprit.

If you don't think so, take a DVM and go measure the voltage drops (like I did).

I fixed the problem by fixing the grounds, not by adding another one.


Furthermore, the GM "fix" does not correct the main ground cable offset.

All it does is connect the grounds to chassis through a big "ground loop" that are now all offset by the main cable ground mounting bolt to battery negative.
 
#146 ·
You know, I have to apologize for sounding condescending. That was wrong of me.

However, in this case, it's not as simple as you make it out to be. Keep in mind the first attempt was a software upload that broadened and changed the limits that were interpreted. This was done clear back in 2004 or 2005. Since this is so sensitive a measurement, the age of the vehicle comes into play. The fix you advocate is just not practical. It's not just a connection, it's the entire resistance measurement of the ground circuit. If you trace that circuit, it's a nightmare to get to everything. Nobody is going to pay $2000 in labor to rip out a wiring harness and repair and replace everything needed. This is so sensitive a measurement that a voltage drop measurement may not be able to tell you what you need. What this repair is doing is running a ground directly to the cluster ground. The circuit originally grounds through the back of the passenger side head, chassis, etc. This eliminates part of that circuit and allows the cluster to properly read the voltage on the circuit. I applaud GM for coming out with such an affordable fix that should work for a long time.
 
#150 ·
The fix you advocate is just not practical. It's not just a connection, it's the entire resistance measurement of the ground circuit. If you trace that circuit, it's a nightmare to get to everything. Nobody is going to pay $2000 in labor to rip out a wiring harness and repair and replace everything needed.
I'm not sure what you fix you think heavymetals is advocating, but the fix I think he's advocating is cleaning up a couple of pretty easily accessible ground points in the engine bay. It doesn't cost $2000, it costs about 27 cents (for a few star washers) and maybe 15min of your time. And it works (or at least helps).

What this repair is doing is running a ground directly to the cluster ground. The circuit originally grounds through the back of the passenger side head, chassis, etc. This eliminates part of that circuit and allows the cluster to properly read the voltage on the circuit. I applaud GM for coming out with such an affordable fix that should work for a long time.
I have that "fix". It helped a little bit, but it certainly is not the final answer. Before the additional ground was installed, my oil temp would jump 45-50F instantly when I turned on the A/C. With the additional ground installed, it would only jump about half that much. With a few grounds cleaned up in the engine bay, it only jumps 5 or 6F.
 
#147 ·
It wasn't condescending, it was insulting and I edited it out.

That's what happens when you insult a mod.

As for the software "fix", GM figured that it could correct the problem by raising the overall offset, which is not a fixed value (the offset) as it changes with the amount of load drawn through the junction of the main ground, air conditioning and lights being the big draw.

Adding a redundant ground, does not "fix" the bad junction between the negative ground bolt and the battery cable, it only masks it and creates a big ground loop.

Also, aluminum is a funky conductor.

I did trace the circuit.
 
#149 ·
I can add a data point. Not long after a bought the car (over a year ago) I did the star washer mod to the ground cable next to the hood strut. I wasn't having any problems at the time but I prefer preemptive maintenance. Back when I was combing over the car to benefit from the end of my CPO warranty, I also found some bare wires in the oil level sensor harness and I believe the dealer spliced in a new pigtail. There were no over temp alarms at this point, but that plug HAS been replaced, so it may be a contributor to my continuing good luck.

Sometime later, when I was doing plugs, I cleaned up the ground at the back of the passenger side head. I still wasn't having any problems.

Finally, I drove the wheels off this car last weekend, including the Dragon, and the highest temps I saw were around 280F, which I believe was probably not too far off reality.

If the ECM doesn't use oil temp, does that mean the OLM calculates oil temp, instead?
 
#151 ·
The bulletin being quoted was released in 2007 to correct a condition where the temp reading was "pegged".

The reason was a bad ground (INT or NO GROUND).

The cause was probably a bad connection at the crimp in the connector but whatever.

Reed has pointed out, as you have, that his car exhibited this exact problem and he had the dealer fix it, which they did, and I presume by the bulletin.

I stand by my "fix" that the bad connection at the primary ground is the cause for FLUCTUATING TEMPERATURE readings.

Outright failure, ie "pegging" the meter is the result of NO GROUND.
 
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