DanaT

I was driving my '04 CTT home and had a little boost then the pig fell flat on its face and barely ran. I pulled off to the next street. Luckily I was close to home. The PSM fault came on the dashboard but no CEL.

I grabbed my trusty ford Pickup and went back to the pig and hooked up Durametric.

The failure codes were misfires on all cylinders (p0300, P0301m, etc).

The top error code was

P0102 - Mass or Volume Airflow Circuit - Value below lower limit value.

So to get the CCT home, I unplugged the passengers side side MAF and the CTT ran just OK. It was little rough, but it ran and go go normal speeds.

Of course unplugging this gave me a CEL.

BUt what is strange is also with the MAF unplugged, there was a PSM Failure on the LCD display. This seems strange, but maybe in open loop PSM doesnt work?

That said the CTT has two MAF sensors. I dont want to replace both if I dont have to. Does anyone on here know how to determine easily (not swapping parts) which MAF is bad? I have a durametric if that can be used to test the two MAF sensors. I probably have to hook the one up again?

TIA

DanaT

I think I might have answered my own question.

I found the first MAF sensor output in Durametric.

Scrolling down, there are two more. MAF right and MAF left voltage.

I just need to try these out.

XR4Tim

I believe these faults can also be caused by a boost leak. You very likely could have popped a boost hose off of one of your intercoolers.

DanaT

That is a good idea to check...

My 951 ran like this when a fitting blew out of the intake manifold.

Being that the car was coming up on boost and instantly did this, it is quite possible that this is and issue.

Are the Cayenne Turbos prone to having boost hoses come off?

wrinkledpants

Have you tried completely disconnecting one MAF at a time and seeing how it runs? That's usually what you would do in other cars.

I'm not quite sure how a MAF code would be a boost leak. There is no air flow measurement after the MAF, so if you're leaking boost, it shows up as a boost code, or some other issue.

What air filters do you use?

DanaT

It runs "OK" with the right MAF disconnected. I havent yet disconnected the left MAF.

I am using stock Porsche filters. Car is 100% stock.

What is strange is my MAF reading with the durametric. I get 1.0V on both right and left MAF sensors when connected when running. There is no variation. When I disconnect the right MAF, left has 1.0V and right has 0.0V. They dont move. I would suspect that the MAF voltage would move.

But the MAF output (kg/min) does change with rpm so it seems to be doing "something"

wrinkledpants

There is a lot that goes into a MAF and the feedback it gives the ECU. I would try disconnecting one, the other, both, and see what happens. I'd also swap sides with the MAF's and see if the code follows. If it does - I think you have your answer.

Cole

Check the plastic hoses at the front of the engine. Mine cracked from age/heat and produced a very similar set of symptoms.

DanaT

I did not see any obviosu cracking, but I will check carefully.

I have two new MAFs on order so this weekend they should be here.

With 50K on the odometer, they probably are near the end of their life anyways.

DanaT

Off topic Cole, but did you ever find a place for reasonable priced upgraded intercoolers?

Cole

Apikol said thy would build a custom set for reasonable money.

Fwiw, it was this hose under the front plastic trim piece. It was cracked on the bottom where you wouldn't see it.

DanaT

I will check that hose...

A boost hose makes sense since the car was coming up on boost and then instantly fell flat on its face.

I dont know if a MAF would do that...

But having spare MAFs on hand, if this is the problem, isnt a bad thing.

DanaT

Did the IPD "Y" give you the extra 30 hp they claim? You should be able to feel 30hp.

DanaT

Unless it is a very small crack, I cannot find it by feel. I can feel the hose all around and I dont feel any cracking.

How big was your crack?

Cole

Probably about 1/2"