A5 B8 cranks but wont start

[SteveQ]

Hello Everyone

This is my first post .I hope someone can throw some light on my problem.

My A5 B8  3.2 fsi had been 

really good. Because of using it as a second car the battery started to loose its cranking ability. No problem it always started with a jump start.

I then bought a Topdon starter which seemed great.

But being in a rush one day I connected it with the polarity wrong. I dont think I pressed the button but could have.It obviously didnt start.

Since then the car cranks fine but wont fire.

I did find the pyro fuse was missing and the small connector had a resister added. I have reinstated both now and fitted a new alternator in case it has been damaged.

Obd eleven is not telling me much either

Any help would be much appreciated . 

 

[Steve Q]

Could it be an imobiliser issue? Any warning light on the dash? 

If it's not imobiliser then could it be an issue with cam sensor? 

[SteveQ]

Hello Steve Q.

I did think  it could it be an immobiliser fault but wouldn't  have a clue where to start with that to check it.

As for the camshaft sensor. I think there are four on this engine. I have changed the crankshaft sensor since the starting problem began.

Im worried it could be an engine ECM / ECU problem. An OBD eleven scan read an over voltage situation PO68700 was detected.

The engine warning light has been constantly on since the car wouldnt start.

Thanks for your ideas by the way 

 

[Steve Q]

No probs at all, from the fault code detected I wonder if the ECU is now defective. 

[SteveQ]

I hope it wasn't the Topdon

starter pack that did the damage. It does have built in protection against a wrong polarity connection.Or so it says.

Perhaps the boost it gave after that was enough to fry something in the ECM.

The lack of pyro fuse might have contributed to that maybe.

 

 

[Steve Q]

I'm not sure but I'd recommend getting the car checked by an Audi specialist or an auto electrician 

[SteveQ]

Yes I think you're right.Maybe a proper VCDS

scan would identify the fault precisely.

I did call in at a local vw/audi specialist but wont come out to scan.

I can't believe that all this could have been caused by that Topdon starter.  They must sell 1000s of them and there's no trace of a similar problem online.

Can anyone suggest a mobile VCDS  scanner 

I'm in east herts area.

Thanks for the input Steve Q