2.7T Avant Manual won't start...

[eejit]

Hello, first post, hope this is the right sub-forum, etc...

I've recently got myself a 2002 A6 Avant, 2.7T Quattro Manual (about 2 months ago). Prior to this I've had Mondeo's and Volvos and have been able to do work on them myself (so I'm quite disappointed to find out that there's no Haynes Manual for the C5 A6!).

Recently it's been taken longer to start, and having come back from a holiday is now completely failing to start. The starting process sounds absolutely normal, it just will not take. A quick google throws up this thread from here, which seems to match my symptoms. I have read the OBD and it is showing an EVAP flow rate incorrect code, so I have three questions:

1) Could the EVAP code cause the car not to start? It seems unlikely from googling this.
2) Would a water temperature sensor create a fault code? I have an Autel EU702 for reading more codes than a standard OBD but haven't had the chance to use it yet as the car's in another city.
3) Is there any other common causes I could have a look for?

Many thanks.

 

[eejit]

OK so I've read all the codes I can with the Autel EU702, it comes up with the following codes:

17861 - P1453: Exhaust Gas Temp Sensor 1 (G235): Open or short to plus.
17865 - P1457: Exhaust Gas Temp Sensor 2 (G236): Open or short to plus.
16825 - P0441: EVAP Emission Control Sys: Incorrect Flow
18010 - P1602: Power Supply Terminal 30: Voltage too low

I'm guessing if my Water Temperature Sensor was faulty I would have a code for it? So I'm going to have to assume that one of these codes is causing my start issue. I can write off the P0441 code, as a bit of Google-Fu would suggest that it won't cause the car not to start. Again, Googling P1453 and P1457 would suggest that if those stop working the car would just assume that they were at the maximum temperature and overfuel, again not causing the car to not start. Can anyone offer an alternative opinion on that?

That would leave me with just P1602. Now the battery is definitely dead - I connected a power pack to it today to crank it, it was definitely only cranking off the power pack, and when I unplugged the power pack I watched the needle drop from 8-10V to zero in the space of about 3 seconds. I assumed that like the OP of the thread I linked to in my first post, that's because of having to keep cranking it to get the engine to start and that getting steadily worse, but now I'm wondering if the battery was dying before and that was causing it to be progressively worse at starting? My issues with starting the car started about a two weeks before it failed to start entirely. Any thoughts?

 

[eejit]

Incidentally I have a replacement coolant temperature sensor because it wasn't expensive to get - is it worth just changing this anyway even though there's no code?

 

[eejit]

Have now replaced the battery and still won't start, so it wasn't the battery. Have unplugged the temp sensor and tried to start it and it won't, so I guess it's not the sensor that's faulty? There was some corrosion around there though.

I also cleared all the fault codes in the hope that it would leave a single fault code for whatever's causing the car not to start, but now there's just no fault codes. What's that about?