[NPAKV10]

2004 Touareg V10 TDI
Recently my car has been having an issue starting and showing a low voltage. In VCDS I checked the battery voltages and the accessory battery shows 10.8v (dead) and the starter battery show N/A. I manually checked the started battery and it has a voltage of 12.7. I assumed that when you when to start the car it would switch over to the starter battery and use that to start the car. I can hear the solenoid click on in the back when trying to start the car but only get a slight chug and then nothing. I did check the isolation switch under the drivers seat and it is showing the copper coil in the sight glass. I don't know if this is just a 2004 thing that it doesn't show the voltage for the rear battery or what, I have search and searched but couldn't find anything on VCDS not showing voltage for the starter battery.

Also does the battery need to be re-coded if replaced, I have seen mixed opinions on this and VCDS times out when trying to get into the sections that are in the given instructions that I have seen.

One other thing if put on a charger the car will start and run just fine through out the rest of the day and then over night go dead. I assume that there may be a bad cell in the battery, it is 8 years old and hasn't had any issue prior to this.

Thank you,

 

[lgibson]

You do know the starter battery is the rear battery? The battery switch may not be good. Bentley made a big deal about disconnecting and reconnecting batteries in the proper sequence for 2004 V10’s to avoid damage to the electronics. Have you tried turning the key counterclockwise before clockwise to start?
All that said, I would replace the old battery. I monitor battery voltages in central electrics (09) measuring blocks IIRC.

 

[NPAKV10]

You do know the starter battery is the rear battery? The battery switch may not be good. Bentley made a big deal about disconnecting and reconnecting batteries in the proper sequence for 2004 V10’s to avoid damage to the electronics. Have you tried turning the key counterclockwise before clockwise to start?
All that said, I would replace the old battery. I monitor battery voltages in central electrics (09) measuring blocks IIRC.

Yes I do know the one in the rear is the starter battery, did some research on that because I was super confused on why the voltages we different in the batteries.
I did try turning the key counterclockwise first but I will do it again just to be 100% sure (its been a busy day today).
One other random thing I noticed when looking up the isolation switch, there is a plug on the end of it, would that plug into an electrical plug that has foam over it? I found that plug under the seat but at the time couldn't figure out where it went.

 

[nickyt]

There are two measurements needed to verify a battery is good. You do have a good resting voltage, however you also need a good load current. With the information presented, we can not give the battery a pass, yet. A heavily sulfated battery will show good current, but not deliver any electrical current.

You do not recode the batteries on the T1 and the T2. They charge the batteries the old school way.

The VW BEM coding is for the later year Touareg models, not the earlier years.

 

[NPAKV10]

load tested the battery and it was shot. Bought a new one and got it installed and now have a new problem.
ABS light, Hill Assist, Brake system warning stop car blah blah blah and a few other warning lights and the car is stuck in park.

Starts just fine and runs like a champ just doesn't move like one. (Trying to positive humor).

Tried clearing the DTCs and still no change.

I didn't attach a charger when switching the batteries and I'm now kicking myself for not doing that.

 

[lgibson]

Did you disconnect front battery before connecting rear battery, per Bentley?

 

[NPAKV10]

Yes I did disconnect the front before disconnecting the rear.