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Help please - p1145 and notIced a small crack in the header

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Hi All,

I am a new owner of a slightly modified 2003tt and love it. I bought it about 2 months ago and just last month the check engine light came on. I went and bought the durametric entusiast cable (which I read about here - thanks to everyone) and read a p1145. I watched the o2 sensors while the car was running and they seem good (voltage fluctuating and both bank 1 and bank 2 seem to have simular readings.) I did notice the sensors after the cat have spacers. (PPI didn't state that and I didn't know a thing about it until reading forums).

Anyway a long story short I was reading the maintenance records of the car and noticed one mentioned a small crack in the aftermarket header (oh yeah techart headers and exhaust and I believe k24 turbos and GIAC flashed) - anyway I looked and in the collector of the bank 1 header it looked like a small black line which I assumed might be the crack.

Would a crack in the header cause a P1145? Any other good checks? Car seems to run fine but rich at startup. Lots of power.

Any help would be great! Thanks all!

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  • Admin


P1145 Oxygen Sensor Ahead of TWC, Bank 1 – Above Limit

Possible fault cause

- Valve lift fault

- False air on the oxygen sensor after TWC

- Oxygen sensor

Either way you need to replace the cracked header - then clear the code and see if it comes back.

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Thank you very much for the information and the welcome! I have thought about trying to get it welded. Any thoughts?

As for stock headers - I didn't think they were tuned like aftermarket ones?

There is so much to learn - really love this site.

Thanks again!

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As for stock headers - I didn't think they were tuned like aftermarket ones?

You can't tune headers...the best headers are the ones with the shortest length and least restrictive to airflow (reducing back pressure). TMK, the stock headers for the turbo are the shortest ones out there. Port and polish the stock headers and you are good to go to about 700hp.

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As for stock headers - I didn't think they were tuned like aftermarket ones?

You can't tune headers...the best headers are the ones with the shortest length and least restrictive to airflow (reducing back pressure). TMK, the stock headers for the turbo are the shortest ones out there. Port and polish the stock headers and you are good to go to about 700hp.

Totally agree with Wross. Port and polish the stock headers.. Aftermarket Headers for Turbos (996 and 997) are VERY expensive and a waste of money.

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That's exactly what I was thinking (wasn't sure but I know air passing over a surface at high velocity can create a vacuum). Plan on bringing it in to my local Indipendant.i talked with him and he thought welding it would work.

Thank you!

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  • 1 month later...

Finally getting around to getting the work done. Getting the header welded (I know against many smart people) I had a long talk with the owner of the Indy shop with me saying stock headers are fine to go to - he said his welder was fantastic and it would not crack and send flakes into my turbo. Praying he's right. Regardless once I get it back and drive for a while I'll let you guys know if it comes back.

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  • 3 weeks later...

You know I have a durametric. Couldn't I just use it to test the o2 sensors? Also I've noticed about 1800 type 2 overrevs (thati thought was from the previous owner/giac rev limiter change - don't see any with my UMW tune). Regardless would type 2 do damage to lifters? And um that sounds expensive. :/

Thanks guys for the information you give - it is very appreciated.

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More information: before I bought the car I had a PPI done with a leak down test. All cylinders were 5% except one that was 6%. Thought that seemed good. The CEL wasn't on at the time but afterwards the person I purchased it from mentioned it and said it was the O2 sensor. Of course I was maybe too trusting and believed him. Of course it could be that.

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More thoughts:

- False air on the oxygen Sensor after TWC

Figured out TWC means the catalytic converted (three-way catalytic converter) - so it seems having spacers on the o2 sensors after the TWC certainly could do this. Sigh. Maybe remove spacers. (previous owner had the spacers installed).

I wish I knew exactly what is meant by "false air". I feel another visit to google coming on. :)

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False air: air that enters the induction system but had not been measured by the Mass-Air sensor. The result of false air will be a too fast or erratic idle.

Okay did the MAF test (using the durametric and Following the voltage guidelines on here.) off it reads just above 1.0v running it fluctuates a bit but like 1.42-1.44. Didn't wait until it was hot. So anyway it seemed to pass that test but my idle with AC on or off is at 820-840 rpm (I have a umw tune so that may be correct)

Anyway just posting information - hopefully this may help someone else in the future!

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  • 2 weeks later...

Well it wasn't the MAF. Replaced and cleared the code with the durametric. It certainly idles smoother and runs better but still has the p1145 code. Next I have the o2 sensor after the cat on order. I will replace and report back (wish I knew if it was the spacers!)

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  • 1 month later...

No much - I changed out the MAF with a new one, got the same code and MAD seemed to go bad in a month (got a p0102) some quick research showed it may be the wrong model. Regardless I used some MAF cleaner on the old one and just put it in yesterday and cleared the code. Running well but really expect it to come back.

I read a recent posting on another forum which suggests a boost leak (that person was getting other codes along with the P1145).

Once it is time to do the breaks (soon) I will likely bring it to my Indy to do a fluid flush and let him try and diagnos (a different Indy suggested the GIAC coding which has been switched to UMW now and still throws the code.)

I haven't forgotten about this thread and will keep it updated with info. I'm glad there are people reading it. I wish I had better info. Any suggestions are welcome!

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  • 2 weeks later...

Hi Loren!

Had the headers welded. I checked the o2 sensor and i can see when in neutral and do a rev then a auick stop the voltage on bank 2 goes much lower. Maybe a lazy O2?

So now i am tired of the CEL and since I do not have the time to dedicate to it I am going to take to my Indy for his diagnosis. I'll post results!

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Well he (we) replaced the o2 sensor before the cat and did some data logging. It looked much better (normal) than the sensor replaced (the old sensor never went below 1 volt unlike bank 2) now they match more closely. However after about 35 miles of driving its on again with p1145. (Also p0430 but I believe that is unrelated? Different bank and cat efficiency)

Taking it back in tomorrow. More posts to come!


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  • Admin

P0430 TWC Conversion, Bank 2 - Above Limit

Possible fault cause

- Oxygen sensor ahead of and after TWC exchanged

- Valve lift fault

- Aged oxygen sensor after TWC

- TWC faulty

Odd to be both banks.

Sounds like a leak still (intake and/or exhaust).

I suggest you have a close look at O2 sensors pattern at idle, low RPM, and then at 4000 RPM.

Any other mods?

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