i have a 2000 A4Q 1.8t (ATW) i've had this CEL for about 3 months now. i have been reading up on it and i finally decided to do something about it. first i took my car to a mechanic to get a smoke machine hooked up to it to look for vacuum leaks and all the smoke went straight out the filter on the leak detection pump. so they said that my leak detection pump was bad cause it should be closed while the car is off so the smoke shouldnt be going straight out the filter. so i got another pump from a junkyard and it didnt fix anything. so then i bought vag-com so i can run the evap test to see what i get. well i cleared the codes, then let the engine idle for a little bit. i then ran test 070 under basic functions and it said "evap ok" so i then ran test 071 and it said "system not ok". i read a post saying to check for power and ground on the 2 wire electrical connector while your running the evap test. well first off, i have a 3 wire connector not 2 wires. secondly, you cant disconnect the electrical connector during the evap test cause then it says "open circuit" cause the pump isnt connected anymore so the test obviously wont work. so i ran the test and felt and listened to the LDP and it didnt do anything at all. so i'm assuimg that either the pump is bad or its not getting power. well i already swapped out the LDP with one from the junkyard and it didnt help so i'm thinking that the pump isnt getting power. i got out my multimeter to check for power and i couldnt find power on any of the wires....but im also not sure if i had a good ground. but my question is this.....what provides power to the pump? what fuse should i be looking at? any relays or anything that is involved in the system? where should i be looking at to search where power stops?

 

bump...need some help with this still. had CEL for couple months now and getting very annoyed. i bought a new N80 valve (purge control valve) and that still didnt fix it either...what else can it be??

 

im chasing the same CEL.

 

yeah its pretty annoying and i guess its a faily rare problem cause nobody seems to know too much about it

 

There is a vacuum line from engine compartment to the LDP (leak dectector pump). It may be disconnected or broken somewhere or check valve installed in reverse or bad vacuum reservoir. When performing the basic setting 071, you should hear clicking noise if you put your ear on the fender where the LDP is mounted. You said you have smoke machine, you can use it to locate the leak. If you can, inject the smoke at the vacuum hose at the pump back to the engine.

Yes, the LDP electrical connector has 3 terminals. Two for vacuum switch and one for Reed switch.