Hi everyone,

Can I ask for a "hands up" on pulling together into a single thread all known issues resulting from loss of battery power ... I know that many are correctly noted in Owners Manual; many more throughout the thousands of pages of Workshop Manuals TSBs, Update Notes, and these forums. Not trying to reinvent knowledge - simply to bring it all together into a single resource that can be printed out as a workshop or glove-box reminder along with the car's maintenance schedule.

Here are some examples for you to think about ...


Unexpected Warnings & Codes:

Often and without prior warning, strange and/or unexpected notifications or symptoms may alert the driver to one or more sudden faults in either the drivetrain or discrete control modules. The car may exhibit strange instrument panel behaviour, warning lights or messages, perhaps only clicking noise behind dash -

1. Before ordering new engine/gearbox - check battery on load (>12.5V?)
2. Charge battery overnight; re-test under load - refit or replace;
3. Check test "new" battery under load - rarely are they sold "fully charged";
4. charge overnight then re-measure under load and fit into vehicle;
5. Observe ALL reset or calibration issues after battery replacement.

Reset and/or Calibration Issues:

Following interruption of battery power - whether temporarily for safety reasons or replacing a flat battery - there are several known issues that owners need to be aware of

1. user input of radio access code;
2. reset of user memory of radio presets;
3. reset of seats, mirrors, pedals, steering memories;
4. reset of local/global window auto functions;
5. reset of local/global doorlock security functions;
6. reset of keyfob functions to both above;
7. calibration of EPB function.

The Special Case of HIDs:

1. first disconnect battery, then remove/replace 1 headlight = no problem;
2. battery still connected, then remove/replace 1 headlight = no problem;
3. first disconnect battery, then remove/replace 2 headlights = no problem (but need to verify this);
4. battery still connected, then remove/replace 2 headlights = controller lockout, can only be fixed by dealer reset of internal firmware.

A note to our Moderators - I am guessing that the sheer volume and diversity of contributor posts points to the need for a better understanding of these issues. If vindicated by member feedback, I would be happy to pull it together but need help to make it happen.

Suggested format to specify fault/issue > solution/action > validated link.

What do you think?

 

Great idea!

 

For many repairs, the battery ought to be disconnected. Not only is it safer (avoids risk of severe fire or damage to modules) but the workshop manual often remembers to say it should be disconnected (pretty good for a manual that's only aimed at trained people).

Yes it's a bit of a nuisance. It's worth people understanding that failing to disconnect it is a risk only sometimes worth taking, I feel.

Don't leave key in ignition (let alone On) if you're disconnecting the battery!

Why? Well, heard that noise when you put the key in - it's a big clue that things are live.

So, before disconnecting the battery make sure the key is out of the ignition and I strongly suggest out of the car interior.

Oh - Make sure your key opens the trunk (boot) lock!! If not, get one that does.

 

Great info JagV8 - all your input essential, but you are especially right to point out safety issues, and reinforce cautions in workshop manuals. Thanks also Mikey and abonano for your interest and support. Perhaps I should PM others like Gus, Graham (GGG), Norri, Thermo - I don't know - who else.

I reckon the key to this project is to identify each and every issue, then validate each with a source reference First stage is to inspire as many of our tech gurus to post here as much accumulated knowledge on low power > battery replacement > what to reset as possible - I certainly don't have it all, but I am willing to pull it together.

Please help however you can - 4 of today's top 5 threads all point to this one issue. It may not be sexy ... but it seems there is a need especially among newer members, and perhaps more than they realize. I see people like you chaps constantly repeating basics, when a single reference thread may help spread the word.

Best wishes all.