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Seeking help from experienced Porsche 986 owners

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Good day to all,

I am new to this forum with a limited to fair bit of understanding of mechanics of a Porsche...just bought one a couple of weeks ago its a 2000 model with about 130k miles on it already.

I did go in for an inspection and failed as I had the following codes: P1126, P1128, P1130, P1133,P0650,P0150, P0420

The CEL on the dash just does not come up..guess the led has been either tampered with or just not working and needs a bulb replacement...just not sure

I am seeking advise from all you more experienced Porsche Owners on what do you suggest be the next steps...I know I will get ripped out at a Porsche Dealer. Are there any DIY steps I could follow and try the elimination method of managing 1 error code/group of codes at a time, kinda lost

Look forward to your guidance

Many Thanks,


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As I see it, you have a Mass Air Flow sensor problem and, after combustion, a bunch of O2 sensor problems. If the MAF isn't working, I can see the fuel/air mixture being seriously fouled up leading to some seriously confused O2 sensors. So I'd start by looking at the furthest upstream problem as it needs to be right or it can affect all the readings after combustion.

P0650 says there is a connection problem between the ECU and the MAF and it can be in either the wiring and or the connection.

If you don't have the factory manuals, some hints can be found at Info on the MAF site. The disconnect doesn't say the MAF is bad, more like it can't be seen by the engine management computer so you need to look at this first.

Could be disconnected wires, chewed by rodents, all sorts of things.

I'd also look at the air cleaner not because it should cause any of these codes but just because it is the first step in the air coming in to be measured for computation of the air/fuel mixture.

It is odd that the CEL isn't lit with all these serious codes. Are there any mods to the car (air cleaner, headers, modified cats/exhaust)? Could someone have pulled the light bulb behind the CEL?

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Thank you so much for your response, truly appreciate your help here.

I will do a step by step and get the Air cleaner, MAF, O2 sensor and ECU checked for any issues and connection problems.

As far as I know there are no mods, however the CEL being pulled out is a possibility - the guy at the DMV had a strange reaction to this too and suspected that the bulb has been pulled out. Are there any guides available to replace these bulbs?

Many thanks


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Does your secondary air compressor come on at start up? At the initial start up do you here a sound from the passenger side that sounds like a vacuum cleaner then goes off at about 30 seconds? Breaks in hoses, malfunctioning diaphragms, broken vacuum tanks in this system can all cause the codes you've published.

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Here is a quick update on stuff I have worked on so far... I did manage to open the instrument cluster and noticed that the CEL bulb has been removed - annoying!!!

Also, have changed the Air Filter, cleaned the MAF...they seemed to be in new condition... I just wanted to be sure I do the right thing though. News is that the CEL (that was missing and I replaced it) is still on. I am now beginning to guess that it could be something wrong with the O2 sensor, catalytic converter, lose connection, etc

I was just wondering that if I use a OBDII tester and clear the codes will that help in anyway?

Ronald: Thank you for your response, I have not noticed any of the items mentioned in your note, but I will keep a close watch to see if something on those lines do happen

Will keep you all updated!


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If your secondary air pump is not coming on at start up you can clear all the codes you want and replace and or clean up everything but it will not fix your problem and the codes will come back. Do yourself a favor and check to make certain that system is working. This is advice from someone who had those same codes and spent over $900 trying to fix the problem when all it was was a $0.25 hose that was disconnected in the secondary air system.

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Thank you everyone for all your guidance, here is a quick update on the car so far:

I did clear the error codes and the CEL bulb and as discussed here they did come back after 50 miles, infact I did go in for a state inspection and following is a report: Error code - 0420, 0133, 1130, 0150

the following items showed not ready: Catalytic Converter, Evaporative System and Secondary Air Injection, everything else seemed just fine (02 Sensor, Fuel System, Engine Misfire)

There is also another issue that has occurred as on friday, i.e. when I start the car and rev it the rpm does not go above 2000, I have to keep trying for about 15 minutes (wait for the oil indicator to settle, etc) and then one fine moment it will start working just fine...the first time this happened i heard popping sounds twice when i rev'd up the engine and no popping sound after that.

The start up issue/cold start issue still continues though...could all this be still an issue with a lose connection or would you suggest I show the car to a mechanic or are there any DIY items I could still try

Thank you for your time reading this post!

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When you clear the CEL codes, the car needs to be driven for some the to remove the not ready flags? BMW has BMW FTP driving cycle that if you execute it will make the not ready flafs to ready.

As for the technical portion, The most that my car had at one time were P1128 and P1130. Cleaning MAF fixed for 2 years. The second time, replaced the MAF. Some say that cleaning the MAF works for couple of time, the it needs to be replaced.

Good luck

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So you have a sensor that isn't responding as quickly as a new one would (P0133), one whose signal is not within expected limits (bad sensor, bad wiring, bad ECU???) (P0150), a code showing your catalytic converter is suspect (How long has the CEL been on? Could it have dumped so much bad stuff into the converter that it fouled it?)(P0420), and the P1130 has multiple symptoms;

Incorrect signal from MAF sensor

Intake air system leaking

Fuel pressure too low

Volume supply of fuel pump too low

Fuel injectors fouled

Exhaust system leaking

So lets ask a few basic questions... when did the symptoms start and is the car stock and has there been any work done on it recently? And the answer is you just bought the car and so there aren't any real clues.

So you can shotgun parts starting with 2 O2 sensors which typically last around 60k miles. The previous owner may well have just ignored the CEL, removed the bulb to sell the car after giving it to the dealer after a test ride when it had all warmed up. And an accumulation of miles with non functioning sensors eventually dumped enough unburned gas into the cats that they are damaged. You can also look for air leaks into the intake system or out from the exhaust ssytem ahead of the front O2 sensors. See my article on O2 sensors and alternatives to the Porsche-branded parts.

Or you can go to an expert Porsche mechanic (doesn't have to be a dealer) and have him help you diagnose the problems.

Or go back to the guy who sold you the car and ask him to refund the sale due to the fraudulent emissions system tampering you discovered. Good luck documenting it.

Edited by mikefocke
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  • 2 weeks later...

Hi all,

First of all thank you for all your help and guidance (will need it further too) and sincere apologies for the delay in responding. I will continue to write and share my experience with you all until I close loop.

Here is an update so far...

Ran a bottle of techron, reset the codes and they were back after about 40 miles....I was told by a local mechanic that its the O2 sensors...got them changed (thanks to you Mike for the details in your article), I did get rid of the error codes P0150, P1133, P1130. After driving for about another 50 - 60 miles, I have now got the CEL back on and P0420 and P0430 error code (The P0430 was never there all this while...not sure what triggered this)

I have now taken the Boxster to a Porsche Specialist (Provost Motorsports) and when he attached the PST2 reader the cat converter showed 3.74 reading (not sure what this means...any guidance would be helpful) and they further diagnosed the following (took this description from the Porsche Specialist so that I can write it here):

  1. The oil fill tube is leaking (there are 2 tubes, the one that is leaking is not on the fire wall and takes more labor to replace, the tube OEM part costs $40)
  2. There is a air/vacuum leak - whenever he moved a particular tube/pipe in the engine it would make a very low "hisss" sound

Though with these codes, ironically the "System Readiness" now shows the Cat Converter as "Ready" and the only thing that is Not Ready is the Secondary Air System

So in a nutshell I have a P0420, P0430 causing the CEL and Secondary Air System - Not Ready

I do have an appointment on Monday 10th Sep to have the above 2 points fixed and we are hoping this solves the issue, anything I am likely to be missing here? Any guidance would be helpful...



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  • Admin

Thank you for your response, will certainly share this thought with them...I am hoping this should fix the issue and help me clear the state inspection :)

Please realize that after correcting the problem the car must be driven for a number of drive cycles before the system readness will ready (all happy faces). This can take up to a week of normal driving.

This is an EPA requrement so there is no getting around it -- sorry.

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Here is another update...changed the oil tube leak..there was a crack in there, also a couple of c vaccum leaks were fixed...after driving for about 40 - 50 miles I have the CEL on again with P0420 and P0430 codes back on.

In the system readiness monitor it does show that Catalytic Converters are ready, however the Secondary Air System is NOT READY

Do you think its the cats that need to be changed? Any adivce would be helpful

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Thank you for the advice, I have been looking for these and a bit confused as there are 4 parts that come up as Cat Converters...I know I need to change 2 (P0420/P0430), however can you guide which are the 2 part numbers I need to look at. Following are the parts I have come across: 996.113.103.07 , 996.113.104.07 and 996.113.023.06, 996.113.024.06


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  • 2 weeks later...

Hi there...

Quick update...

The Secondary Air system was ready after a couple of drive cycles...however the CEL was still on with a P0420 / P0430 code and me being unable to clear state inspection

I showed my car to a couple of Porsche mechanics and all of them suggested I change the cats...I did manage to find one online aftermarket Cats - "Davico" a pair of cats was to cost me $700 Plus labor ofcourse to have them fitted in.

Finally, I poured in 20oz of Techron, reset the lights and went for a long drive...and guess what??? the I/M readiness monitor was all set to ready with no CEL...I drove the car (Wish I could have it fly) to the nearest Inspection center and cleared the state inspection with flying colors :thumbup:

Techron turned out to be a miracle fluid...Would like to thank every1 on this post to help me sail thru my situation

Would be happy to share my learnings with over 3+ Porsche technicians about Boxsters...Hope I could be of some help to some1 someday :)



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