Hi All,


I have a 2005 A4 B6 Cabriolet (8H) that recently threw a MIL/CEL with EPC & battery light at me. Multi-metered the brand new battery and its +12V or more. Pulled VagCom and got the following:


2 Faults Found:
16825 - EVAP Emission Control Sys
P0441 - 002 - Incorrect Flow - MIL ON
16705 - Engine Speed Sensor (G28)
P0321 - 008 - Implausible Signal


Now the car is dead in the driveway, with a start no crank issue. It has 1/4 tank of high test in it, was running fine several days but had been sitting quite some time before that. Just did oil change & filter, new air filter, new cabin filter, have new fuel filter ready to put in. Been working on a top controller / hydraulic motor issue but these engine issues are totally unexpected. Did have a mouse issue from sitting but all tests indicate not a wiring fault, at least so far (they were living in the airbox, not the cabin).


My biggest question is why after clearing the faults in VCDS does the dash indicators persist? I pulled the N80 to find that it was clogged. Cleaned and applied 12V to confirm solenoid opens and I can blow through it. Tried with MAF disconnected but no change. I also pulled off the ECU-side to the G28 and tested ~900 Ohms from pin 2 + 3 which apparently is within spec. Any ideas or next steps would really be appreciated. I can order a new G28, but if it's gonna wind up being dead fuel pump then why waste the $$. How can I mechanically test the fuel pump or meter it? Also some have said fuel pump relay which I will check today.


This is my first post after reading many many others that have been oh so helpful but I have yet to find any mention of dash lights remaining on.. Seems most people fix theirs with one or more of the things I've tried.

 

Status update. DMM test at fuse 28 shows ~3V at ACC and ~10 on start attempt. Same test results directly at fuel pump power plug (brown is GND, green/yellow is +, thanks ELSA) yields same results, but no hum no grrr all quietlike in that back seat. Pulled the pump without any special tools, see a4mods and also audiworld (really need that Audi bucket from step ~12). Outside, tested with my handy dandy 12V wall-plug super secret expensive test equipment = not even a death rattle.

Off to the wrecker's to pull a pump (because I'm poor that's why).. brb

Side note, confucius says always do fuel filter when you do fuel pump, lucky me I have on hand. For archival purposes, the A4 B6 Cabriolet Quattro has a dumb cross beam that will be in your way. See here, although mine is just torx. Else see here.

 

You mentioned testing the pump with a 12V "wall plug" and no action from the motor. Keep in mind that you need a power source that can supply 12 Volts at about 10 Amps. If you are using one of those small devices such as a cordless phone power supply, it won't run the pump. You've got to measure the voltage while the power adapter is connected to AC and the pump terminals. Unless you find 12V while attached to the pump terminals, that test is a wasted effort.

 

turbo510 thanks for the response, note taken! First I ran with the key on ACC and then start position, measuring V+ at the pump still installed. That yielded the test results needed and the old pump, she has quit. I failed to mention the deep dark whining heard prior here to fore. Agreed that the 10A is beyond the capabilities of my little handy dandy test power source, however the new/used pump pulled from the scrappers just rumbled up with a quick touch of the leads. Looking to install tomorrow but first to deal with the pump cap that does not match up with mine. Fun fun!

 

Pump installed with the help of this little gem!! She fired right up and ran no troubles.

Well we went the requisite 60 miles and CEL/MIL back again. ****

VCDS now shows the following:
3 Faults Found:
16706 - Engine Speed Sensor (G28)
P0322 - 004 - No Signal - Intermittent
17072 - ECM Power Relay Load Circuit
P0688 - 004 - Open Circuit - Intermittent
16839 - EVAP System
P0455 - 001 - Large Leak Detected - MIL ON
Readiness: 0000 0000

What's next?

 

I"d change the engine speed sensor, which is on the block right below the oil filter. one hex bolt holds it in, and the wire plugs in up on the fire wall where the O2 sensors plug in. inexpensive and can't hurt to replace an old one.

 

Had a similar problem, turned out to be a 20 amp fuze was blown. The coil pack wires were causing it to blow. So after buying and installing a repair kit it runs just fine. Just thought I'd share.