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This PI was superseded to update model years.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