2004 Porsche Boxster low oil pressure idiot light ON

infj23

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Make
Porsche
Model
Boxster
Year
2004
Miles
117K
Engine
2.7
Hello all!
Several months ago, the low oil pressure light on the dash started coming on. No rhyme nor reason--no noted consistent situations/circumstances. Oil level fine (applies throughout; also using OEMs suggested oil of European 5W-40).
Just in case the oil filter was crushed/twisted, removed and replaced the filter and topped off the oil. The removed filter was beautiful--no problem. Situation not resolved.
Took it to the dealer who replaced the air/oil separator. Situation not resolved.
Then I learned that there is a piston and spring combination known as the oil pressure relief valve, including that there is an updated version (has a bit of a chamfer at the end). Installed new version of that piston and spring with OEM parts (including the update). Situation not resolved.
Replaced the oil pressure sensor. Situation not resolved.
Took it to the dealer who also replaced the oil pressure sensor. Situation not resolved.
Put an oil pressure gauge on the engine and drove it around. Pressures on the gauge seemed OK, but situation not resolved.
OK, now I got serious. Removed the oil filter, the oil pressure sensor, the oil pressure relief valve, and dropped the oil pan. See attached pics of the oil pan and the upward view of the siphon area. No metal in the pan and everything looked beautiful to me. Nothing blocking the siphon tube screen.
Put it all back together with a new filter, new pressure relief valve, fresh oil, and installed an oil pressure tester. One of the nice things about this car is that, leaving the engine covers off, I could watch the oil pressure test gauge while driving. Oil pressures seemed good. Cold start jumped to about 75psi. At regular speeds, pressure typically 45-60ish, depending on RPMs. After warming up, just above 180F, idle pressure about 12. All of these numbers are consistent with what I read on various online posts about this car/engine.
So, after all this time, and too much money, my guess is the problem is the wire that goes from the oil pressure sensor and turns on the evil red light.
I found a YouTube video that explains removing the instrument cluster, which seems surprisingly easy to do. Is it worth removing the instrument cluster to check for a loose/bad connection and test the continuity from the light to the oil pressure sensor? Is this system as simple as a single wire that goes from the sensor to the dashboard light, or is this more complicated? I could not find a schematic.
Or, any other ideas (other than selling the car!)?
Thanks in advance for your sage wisdom!
Dave
 

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billr

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I don't have time to look this morning, but suggest you try <charm.li> for schematics
 

grcauto

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Wiring diagrams for these need getting used to. Here's an example taken from Charm


Operation CHARM: Car repair manuals for everyone.
Home >> Porsche >> 2004 >> Boxster (986) F6-2.7L >> Repair and Diagnosis >> Diagrams >> Electrical Diagrams >> Instrument Cluster / Carrier

Instrument Cluster / Carrier​


Instrument Cluster - Sheet 2


Instrument Cluster - Sheet 2 (Part 1):​

1736026506




Instrument Cluster - Sheet 2 (Part 2):​

1736331759




Instrument Cluster - Sheet 2 (Part 3):​

1736903939





Diagrams: Other diagrams referred to by name and sheet number/coordinate (i.e. "Instrument Cluster 3/C5") within these diagrams can be found at the vehicle level under Diagrams By Name. Diagrams By Name

pro multis · About Operation CHARM
 

infj23

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Thanks for the schematic but, yes, there is no wire for the oil pressure light! I'll probably be able to figure it out if I pull the instrument cluster off.
But first, based on the history, does it seem a reasonable idea that the problem is not really oil pressure, but the system that turns on the idiot light?
Thanks!
 

grcauto

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Go into that manual and see if you can find how it determines to turn on the light.
It's not just using the oil pressure but the oil level as well. I never worked on more than a handful of these. I think it's calculated.
 

infj23

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Today I took off and apart the instrument cluster to see if I could figure out which wire was coming to the cluster that was turning the light on. I could not--these new fangled circuit boards make the old method of following a wire impossible!
Attached is a pic of the three connectors that connect to the back of the instrument cluster. Left to right they are white, blue, and green. Any chance anyone can tell me which pin, on which connector, is the one that goes to the oil pressure light?
Knowing that would allow me to troubleshoot the wiring to see if that is the problem.
Thanks so much for everyone's help!
David
 

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billr

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As I read it, they are GRY, BLU, GRN => A ,B,C respectively

Oops, it may be C,B,A I can't remember after just peeking at Charm. I'll check...

Yep, I had it backwards, should be GRN, BLU, GRY => A, B, C
 
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