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2003 Passat Battery Replacement

I had to replace the battery on my 2003 Passat (without temporary power thru the lighter) and shortly afterward the check engine light came on. I got a scan tool that indicated three fault codes shown below. Are these likely the result of the battery change and I can reset the faults or should I take the car into a shop to have them checked out? Thanks for your assistance.

16805 Warm up Catalyst Bank 1 Efficienct below threshold
18011 Internal Control Module: Failed Self-Test
00532 Airbag supply voltage

I would say 18011 and 00532 could be caused by low voltage

As for 16805 . . . wait and see

In any case, I would clear the codes and see what, if any codes come back

May we assume the check engine light was NOT on before the battery replacement?

You’re probably going have to take it to the dealer so the modules can be reprogramed.

Here’s what can happen when a battery is disconnected. And as you can see, VW’s can have problems were the modules need to be reprogramed.


What the article in that link says is not universally true. Here in NY state you can have one system not ready to read and pass emissions. Two systems on a 96 car.

Next time you need to swap batteries get one of those battery-powered gadgets that you can plug into the cigarette lighter and will keep 12 volts on the modules.

Those memory savers used in cigarette lighters use a 9 volt battery. But it only requires 5 volts to save the programing in the computers/modules.


The check engine light cleared today (came on after the battery replacement and was not on before the replacement). The Passat never showed signs of impared driving. So, the error codes were likely due to the battery replacement. I will use a temporary battery via the cigarette lighter next time. Thanks for the advice. I appreciate it.

I think you are right Paul, the codes were the result a side effect of the battery replacement. VW designers thought of this problem already, put code into the ecm circuits to fix the problem for you after replacing a battery, all you had to do was drive the car a tad to reap the benefits of their efforts. You’ll probably agree it would have been nice if VW had put a mention of this in the owners manual.