AudiSport4000

Today was a mixed bag. Got the car in the garage to replace a lower coolant turbo line that was seeping. Undid the line and lost all the coolant in the block and then some, so that sucked. Got the line replaced and then had troubles bleeding the coolant system. Seem to have that sorted out though.

This next one concerns fault codes, maybe Frank can help here. I drove the car to the bank to test the cooling system. The light flashed but thats because I was low on coolant, no biggie. Get to the bank, shut car off, go in and do my business, come out, start car and take off. Everytime I hit boost I get a CEL. Strange, I thought, but I figured it was the knock sensor, it did that when I chipped the car. Get home and pull the codes, its that damn air temp sensor code again. But WHY do I get a CEL when I hit boost? Ive never had this happen except when the knock sensor was the cause. Ive had the coolant temp sender code and air temp sender code with NO CEL when I hit boost.

What gives here? I didnt touch that stuff at all today and I was fault code free after I replaced the air temp sensor.

Ugh. Ideas...?

Katman

I'm thiking that you IAT sensor is causing your problems again.

I recall there is someting about the ECU severly limiting boost if it sees no IAT.

(Whch makes sense, as too much boost with hot intake air could cause problems).

If you think that there is nothing wrong with the IAT sensor itself, try and figure out if resistance of the sensor shows up down at the ECU connector. After all that's what the ECU is looking at. That will test for any wiring problems to the sensor too..

SJM or similar should tell you how to do it that, or at least what pin on the ECU connector to measure..<ul><li><a href="http://www.sjmautotechnik.com/trouble_shooting/10vcoolt.html#airt">Somewhere in here, on SJM's site</a></li></ul>

AudiSport4000

Saw the 2 things mentioned about the CEL coming on while driving and what would cause it.
Just strange that it happened after I fixed this leak.
Just puzzled because Ive never had the CEL come on at anytime besides when I first chipped the car.

Would it be wise to pull the sensor first to check it? Or go straight to the ECU plug?

At least the car runs and drives fine.

Katman

Me, I'd go to measure a the ECU pins first..
(My ecu just pops out)

From what it sounds like, that IAT is pretty fragile, and I'd not want to be messing with it too much. (I did acidently step on my IAt, and bent the pins! Still works ok though.. :-)

Besides, if the IAT is good, but it's a wiring problem, measuring the sensor itself won't tell you anything..

AudiSport4000

Which I dont mind doing, its just a hassle. I'll get the Bentley out and do a pin test tomorrow at some point, or when I have some time.

Until I get it sorted out I'll be careful with the car, but I always am careful

AudiSport4000

When going to measure at the ECU pin, what 2 pins am I looking for? I thought I was supposed to measure from one pin of the sensor to one pin of the ecu plug?