3 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHPlease help solve P0446
Leading reported evidence
Check operation of both valves above the front right tire
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
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Discussions that performed work without a confirmed outcome
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Performed · outcome unconfirmed · Original poster
I checked the operation of both valves above the front right tire using a 9 volt battery.
Leading evidence: 'Check operation of both valves above the front right tire' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check operation of both valves above the front right tire' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Discussions that performed work without a confirmed outcome
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Performed · outcome unconfirmed · Original poster
Cleaned the MAF a few times due to P0172 & an occasional P0175 code.
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Performed · outcome unconfirmed
typically need to be replaced every season or 25 hours of use.
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Performed · outcome unconfirmed · Original poster
I replaced my gas cap and the purge valve near the intake manifold.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
3 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261026T122219Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
I�ve been battling EVAP codes all summer. At first it was P0455 large leak. I replaced my gas cap and the purge valve near the intake manifold. My car is an 03 C4S with about 92K mikes on it. My idle had been pretty smooth early this summer and intermittently it would flutter. I originally had the cold air intake, but removed it and went back to stock. Cleaned the MAF a few times due to P0172 & an occasional P0175 code. After replacing the purge valve I didn�t get the large leak anymore.
I then started to get the P0446. The next thing I replaced was the tank vent valve. When I would fill up I would only occasionally hear the sound of air being sucked into the tank. After replacing the tank vent valve I think I hear it every time now.
I�ve scoured the forums about the P0446. There are many, but none that come back and say what their fix was. Some recommend blowing out the purge air line. I�ve blown out from the purge valve back to the charcoal canister and other lines. I checked the operation of both valves above the front right tire using a 9 volt battery. Both function properly. One is normally closed and holds solid pressure. The other is normally closed but will open if I blow hard enough. I thought it may have been bad so I ordered a replacement but it functions exactly the same.
If if anyone has any suggestions I would greatly appreciate it.
From what I've only read, you seem to have covered all the bases except, I would change the MAF with a new Bosch part first. Your looks to have gone through the ringer!
Also, this from Pelican
P0446 Fault Symptoms :
Check engine light comes on
Engine stalling or misfiring
Engine performance issues
Car not starting
If one of these reasons for P0446 code is occuring now you should check P0446 repair processes.
Now don't ask yourself; What should you do with P0446 code ?
The solution is here :
Porsche 996 P0446 Possible Solution :
Disconnected, dirty or fouled
spark plugs
are common causes for engines that won't start.
Spark plugs
typically need to be replaced every season or 25 hours of use. You should also check that the spark plug gap is set properly. If your spark plugs look good, problems with your ignition system can also preventing a spark. These can range from a faulty spark plug lead, shorted kill switch or flywheel key damage.
P0446 OBD-II Diagnostic Powertrain (P) Trouble Code Description
P0446 OBD-II Trouble Code The Evaporative System ( P0446 code.
Reason For P0446 Code
The reason of P0446 OBD-II Engine Trouble Code is O2 Sensor Heater Circuit Malfunction.Parts or components should not be replaced with reference to only a P0446 DTC. The vehicle service manual should be consulted for more information on possible causes of the fault, along with required testing.
Main engine trouble code archive on Web.
Hopefully one of the Gurus will chime in.
Do keep us posted!
Thanks for the input. I had thought about the MAF too. My MAF is Reading 5.75 - 7 g/s at idle to about 10 g/s @ 3K rpms. I thought that seems about right. That said it is probably original.
My O2 sensors pass according to my OBD
Fusion app. Do you notice anything here?
Thanks again!
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