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YOUR RESEARCHP0452 Dead Horse is kicking my butt!
Reported or suspected cause
elsewhere
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0
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Read evidence and context
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Reported cause · Original poster
Unless this is a red herring and the issue is elsewhere.
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Performed · outcome unconfirmed · Original poster
Checked fuel sender connector for scorched/burned leads.
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Performed · outcome unconfirmed · Original poster
Either way I inspected my connector and didn't see any issues but I cleaned it with Deoxit anyway.
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Performed · outcome unconfirmed · Original poster
I replaced the vent valve on the neck of the full tube as well as the big valve next to the pump.
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Suggestion
There are many ways you can test it ( if you know how it functions) ...You can cap it off and see if that changes the pressures on your tank pressure sensor, or you can take it off and bench test it for leaking...
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So I can't seem to clear the dreaded P0452 Porsche fault code 99 - Tank pressure sensor. Here's what I've done:
1. New gas cap
2. New tank pressure sensor
3. check for ground fault using multimeter, none. Used deoxit on ground lead anyway.
4. Clear the code and it immediately comes back.
5. Checked fuel sender connector for scorched/burned leads. None. Not even a little bit. Cleaned and reinstalled.
6. Engine runs fine as far as I can tell with no lag, lurching, gasping, etc.
So as part of my engine rebuild I had to drain the fuel from the tank during downtime. I tried to siphon the fuel from the filler neck, but could not due to surge flap. So I removed the filler neck and drained it. I noticed a large foam gasket that seals the neck into the tank. Could that be the next thing I look into? If there's a seal issue, would that cause the fault? If not, I'm guessing a smoke test would be next. My question then would be where do I the smoke check? into the filler neck or somewhere else? Unless this is a red herring and the issue is elsewhere. There are no other fault codes.
Yes, thanks. I read that one before. it's a discussion between a 996 and 986 sensor location. Just to be clear I understand, they mention one under the battery tray where the fuel pump resides but it's for an early 986. Either way I inspected my connector and didn't see any issues but I cleaned it with Deoxit anyway.
They mention short to ground as well in that thread. I did a continuity test from the body to the ground clip on the filler neck/fuel tank pressure regulator. Is there somewhere else I should check a ground short? FYI, my radio won't turn on and both side airbag sensors AND BOTH seatbelt tensioners are throwing faults. Just thought I'd throw that out there since a short to ground would definitely cause those to fault as well. Could be a bigger issue?
Yes the tank pressure sensor is located on top of the fuel tank....but is not in plain view and is hard to see/get to and covered by a foam sound proofing....I hope this is the one you replaced..
That said the purge valve can cause the "Pressure Sensor code" if the purge valve is leaking and causing a slight vacuum on the tank, it will make the pressure value implausible..
Also the purge valve I am referring to is located on the engine above the alternator and attaches to the AOS breather connector or throttle body on 99 cable cars..
Smoke test the fuel tank.
I have a bottle of nitrogen with a regulator that I use for EVAP troubleshooting if you want to borrow it.
If I recall correctly you already have a smoke machine, right?
You can check the actual pressures of that Sensor in PIWIS and probably in Durametric also..
It will show a slight negative pressure or slight positive pressure depending on conditions within the tank.....
I think the units shown will be in Mili Pascals or something... ( it's been about two decades since I have dealt with it..)
These f�ers are expensive too. I like the price on the image shared earlier because Porsche wants twice that retail. I�m going to run a test using my durametric since I don�t have access to a PIWIS.
Here are the Actual Values for anything fuel/fuel tank pressure related from the Durametric. Code can be cleared but comes right back. It does appear to be a ground fault somewhere. I'm going to test the wiring harness at the connector for continuity. For those of you who have taken/replaced this value before know it's a PITA and uses the cinch style hose clamps and is wrapped in a styrofoam shell. Anywhere else I should test for a fault? carbon filter?
The tank pressure Sensor is held on by a single screw and has an o-ring on the bottom.....I think what you replaced is the ORVR valve....
FWIW:: your tank pressure values seem plausible and is showing a slight vacuum in the tank (-28.4hpa= -8inwc or -.4psi) and could be caused by a leaking purge valve like I mentioned before...
Could be plausible as the culprit? I replaced the vent valve on the neck of the full tube as well as the big valve next to the pump. F-it I�ll just keep throwing parts at it. 😎
That's not the way this works, not the way any of this works....lol
I have no idea why you replaced those two parts....neither one is even the tank pressure sensor...
The actual value for tank pressure is showing to be a slight vaccum....is this accurate? maybe, maybe not....can we test it? yes.....
We can induce a known slight pressure and or a known slight vacuum on the tank and test the accuracy of the pressure sensor....( engine OFF..key ON ).
IF there is a slight vacuum being produced on the tank when engine is running it COULD be coming from a leaking purge valve on the engine as I have mentioned several times...
Oh I heard you mention that. I�m selectively filtering it out because it sounds like a lot of work! 😋
As far as throwing parts at it, my level of confidence on functioning parts on this Florida rescue is low. But you�re right, it�s now time to start testing.
It's not a lot of work,( it's actually more work fo me to explain/tell you how to test it than it would be for me to test it and the other associated parts/valves) on the 996 the purge valve is very easy to get to and is located right above the alternator and has a hose that is connected to the AOS breather pipe..
There are many ways you can test it ( if you know how it functions) ...You can cap it off and see if that changes the pressures on your tank pressure sensor, or you can take it off and bench test it for leaking...
One thing you can tell that is obvious is the the tank pressure sensor is not "shorted to ground" or "shorted to positive" because the actual value of the tank pressure sensor a slight vacuum of -28.4hpa which is plausible/believable.........if the wiring were sorted to ground or positive the value would be way way high or way way low...
So either the tank pressure sensor is inaccurate ( not likely) or there is something inducing a slight vacuum on the tank when it shouldn't be ( like the leaking purge valve= very likely) ...
Wait, you're talking about this one? Note the cracked hose attached to it.
Well step one will be to repair the damn leak I uncovered yesterday. I did indeed discover a small crack at the base of the connection barb. I'll update the other thread with some pics. Thanks for your help here.
Yes, that's the purge valve, very easy to get to and test for leaking ( internal leak) .. The cracked hose will not effect the tank pressures, but WILL effect the fuel trims...
BTW : since there are cracks in the fuel pump/gauge housing, they could effect the "tank pressures" and be causing the Sensor values to be inaccurate.... so yes, fix that first then retest !!
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