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3 codes at once (same time) MAF DME Boost Pressure

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Relatively new owner. I bought my '02 996t (tip) at the end of last year. When I bought it threw the ABS PSM lights. After getting it hooked up to a durametric I learned I had the following codes:

4206 Front Left Speed Sensor - Signal Implausible5525 Incorrect data transfer with DME master control unitP0103 Porsche fault code 115 - Hot film MAF sensor

Well thanks to this forum I fixed the 4206 by splicing in a new harness, since the sensor itself was good (swapped left and right and code still came through).

So I thought I was down to 5525 and P0103. So I ordered a new MAF. Once I installed the MAF and cleared the codes I took the car out, put the pedal down and fairly quickly got the ABS PSM codes again.

Current Scan shows:

P0103 Porsche fault code 115 - Hot film MAF sensor

P1250 Boost pressure deviation exceeds limit value

5525 Incorrect data transfer with DME master control unit

So I got another MAF and cleared all codes, took a short trip no codes. On the return, within a minute it threw ABS PSM and the codes above in bold returned.

I am at a loss...

The car has a tune through GIAC, Fabspeed Exhaust, Evoms Intake (new oil-less flter with cover).

Please help...

Edited by magelin
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P0103 Mass Air Flow Sensor - Above Limit

Possible fault cause- Intake air system on pressure side (between turbocharger and engine) leaks- Short circuit to B+- Mass air flow sensor faulty- Throttle jacking unit faulty

When you get this fault PSM is turned off (until it is fixed).

I would start with checking for intake air system for leaks - use a smoke machine if possible.

Highly likely with the changes...

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Do you have the stock air intake / filter box? If so, put it back on and try that. I hate aftermarket air intakes, they seem to cause more problems than they are worth. But the people making them want to sell parts and so they advertise all these positive points. There is way more to a car's air intake than just flowing air. They are also tuned for intake pulses, etc which most aftermarket suppliers dont test. I had a 650+ HP TT with factory stock air intake and filter and the only problem I ever came across was blowing the rubber manifolds that connect the intake runners to the engine; had to have the intake runners strapped down to keep from blowing them out and then the problem was solved.

Loren says air leak between turbos and motor and he may be right. The deviation exceeded code,I think, is saying that there is a difference between the amount of boost one bank of cylinders is getting compared to the other. Or, it is saying that the boost sensor is detecting more boost than what the DME map allows for. In the first case,this gives one side of the engine way more torque than the other and so the car will try to protect itself. However, when this happens the car will usually turn the motor off. Even if you're driving down the street. But in your case it may not be bad enough for a shut-off and may just throw the code.

Have you crawled underneath and checked to see if the wastegates are moving freely? One or the other can bind which could cause this too.

I have a tool that I made using a standard bicycle pump with a gauge and some rubber hose that allowed me to connect up to the wastegates and then pump the bicycle pump and while checking the gauge I could verify at what psi they started to crack open and then at what psi they were fully open. This allowed me to synch them very precisely.

I also have two connectors that you remove the air intake hoses from the turbos, install these connectors with band clamps directly to the turbos and then connect an air hose and pressurize the system and then squirt around the engine with soapy water or even just listen for leaks. Its very common to have leaks especially when running more boost.

I was never a fan of GIAC with TT's. They built a good reputation with the older 911's and so many people assumed they were the hot ticket too when the 996 Turbo came out. This wasnt the case in my humble opinion as I knew many people with GIAC quirks and gltches. I think the best way around some of those issues with tuned cars is to get rid of the factory boost controller, retune the DME accordingly and then install an EBC. Otherwise the car is trying to control boost and is constantly monitoring it and when someting falls out of its parameters it throws codes. Now that is much safer, but more prone to annoying codes.

Porsche peeps are funny. GIAC was so ingrained in the community that many years ago I was kicked off of a forum for trying to seek out a Turbo X50 owner that lived near Atlanta, Ga that would be willing to let APR use their car to create custom maps for differing octanes. APR was going to supply the hardware and tuning for free. At the time, not many people in the US had heard of APR and the Porsche community was clueless. They thought they were some back alley shop that I worked for and kept telling me that anybody that didnt use Giac was dumb and that nobody was willing to risk their investment on "my crappy product" . In truth I didn't work there. They just had the only system that allowed for different octane maps that could be changed via the cruise control stalk in the car and I wanted it but they didnt offer it on X50 cars and so they told me that they would give me or somebody else everything for free if I or whomever let them use their car. So I was trying to find somebody that lived near them and wanted a free tune. I was kicked off the forum for my effort. Go look up APR Tuning and tell me how "fly by night" they look...haha.

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  • 1 month later...

I am back and will be ready to start diagnosing the car. As I do not have a smoke machine would building this work?


Or would this test the "vacuum side" between the turbos and the intake. Sorry if the question is stupid, I am a novice to all of this. Any diagram out there to help me?

Also I am a little scared of doing 25psi so I figured I would set it to 15-20psi to make sure I don't make things worse.

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