tartar

<center><img src="http://pictureposter.audiworld.com/105216/006.jpg"></center><p>I have a 2000 A6 2.8 FWD with 80,000+ miles. I just had a bunch of repairs and maintenances done such as replacement of front tie rods,right front axle, numerous gaskets, numerous hoses, timing belt, serpentine belt, water pump, coolant reservoir, complete tune up, filters, oil change, etc... Lately, I've been getting the following engine codes.

16805 warm up catalyst efficiency below threshold (Bank 1)
16815 warm up catalyst efficiency below threshold (Bank 2)
17704 cooling system malfunction
17831 Sec. Air Inj. Sys., bank 1 flow too low

Any advice/suggestions would be greatly appreciated. I'm just afraid that I would have to fork out more money which I don't have.

tartar

I found this tech article written by Victor Silva regarding replacement of Engine Coolant Sensor which is the apparent culprit generating the 17704 engine code.

https://www.audiworld.com/tech/eng54.shtml

The 16805 and 16815 codes seem to be O2 sensor related issues (I think). I'm still looking up the reason behind the 17831 engine code. Any help would still be appreciated from any of the "pros" in this forum. Thanks.

plova

Hi there Tartar,

The fault code - 17831 (SAE P1423) refers to a fualt in your Secondary Air system. There is an Audi Technical Bulletin out on this code - No. 01-03-08. It might be something as simply as a cracked or broken vacuum line (these are the small, black, cloth braided lines under your engine covers). If these are ok check your secondary air injection pump fuse.

The codes 16805 and 16815 are referring to the oxygen sensor as you mentioned in a follow up post. This can be caused either by the O2 sensor or the wires connecting to the sensors. The repair manual gives directions on how to test the wire to eliminate this problem. These are the two sensors before the converter.

code 17704 can be a number of issues related to the cooling system. I would have thought they would have replaced your thermostat when the timing belt was replaced. It might be either a faulty thermostat or a problem with your Engine Coolant Temperature (ECT) sensor.

Hope this helps.

tartar

Thanks for your help Plova! I will have to let the indie mechanic down the road look into these codes. They did replace the thermostat at the same time they changed the timing belt. If it's a faulty thermostat, they will have to change it "free" of charge.

I will check with the repair manual and see how to test the O2 sensor wires and inspect the vacuum lines for any cracks.

I'll keep you guys posted. Thanks again!

P.S. This morning the "worn brake pads" light came on my dashboard. Man, when it rains...it really rains! Ces't la vie!!!