Quiet fan noise / error 3B97

[z4lincs]

Morning all!

I came back to my zed a few days back to find it totally dead, couldn't even unlock. Managed to get it in manually and hooked up a smart battery charger but after quite a few hours it wasn't taking any charge whatsoever.

Batter was new one in May this year, so got the company to send a new one out which I've just dropped into the car. Car starts ok etc but once turned off there is a very quiet what sounds like a fan noise in the centre of the engine bay which just doesn't go away. My fear is this happened when the car was last driven and is actually want caused the battery to run flat.

Got BimmerLink reader on it and the only code showing is a 3B97. Any ideas before I head to a dealer?

I've disconnected (the new) battery again to stop it running this one down.

[B21]

That error on N20 DMEs is caused by a failure of a data bus link between one or more modules..

Probably the reason why the battery went flat is that the DME couldn’t shut down all electrical consumers.

It’s going to take a pretty knowledgeable Indy / dealer with electrical skills to de-bug it..

Unfortunately the usual trick is to unplug things till the error goes away…then that highlights the fault area..

You could try re-installing a fully charged battery and then clearing all codes and see what re-appears..

Have you done any electrical mods to the cat?

[flybobbie]

Just odd suggestion, is the outside temp. reading correct.
I had to replace my temp. sensor, car did something odd, can't remember what now.

[z4lincs]

That error on N20 DMEs is caused by a failure of a data bus link between one or more modules..

Probably the reason why the battery went flat is that the DME couldn’t shut down all electrical consumers.

It’s going to take a pretty knowledgeable Indy / dealer with electrical skills to de-bug it..

Unfortunately the usual trick is to unplug things till the error goes away…then that highlights the fault area..

You could try re-installing a fully charged battery and then clearing all codes and see what re-appears..

Have you done any electrical mods to the cat?

Thanks! And this sounds fun..

I put on the new battery and cleared a whole load of codes, and it's just this 3B97 one that won't go away.

Just odd suggestion, is the outside temp. reading correct.
I had to replace my temp. sensor, car did something odd, can't remember what now.

I'll hook up the battery again and have a check!

[B21]

That error on N20 DMEs is caused by a failure of a data bus link between one or more modules..

Probably the reason why the battery went flat is that the DME couldn’t shut down all electrical consumers.

It’s going to take a pretty knowledgeable Indy / dealer with electrical skills to de-bug it..

Unfortunately the usual trick is to unplug things till the error goes away…then that highlights the fault area..

You could try re-installing a fully charged battery and then clearing all codes and see what re-appears..

Have you done any electrical mods to the cat?

Thanks! And this sounds fun..

I put on the new battery and cleared a whole load of codes, and it's just this 3B97 one that won't go away.

Just odd suggestion, is the outside temp. reading correct.
I had to replace my temp. sensor, car did something odd, can't remember what now.

I'll hook up the battery again and have a check!

These cars have several data buses both legacy ones then later ones to support more modern devices..they are then cross tied to allow comms across them..great until something probably quite trivial goes wrong..tricky stuff with out data bus analysers ..let us know what you find out..

[z4lincs]

That error on N20 DMEs is caused by a failure of a data bus link between one or more modules..

Probably the reason why the battery went flat is that the DME couldn’t shut down all electrical consumers.

It’s going to take a pretty knowledgeable Indy / dealer with electrical skills to de-bug it..

Unfortunately the usual trick is to unplug things till the error goes away…then that highlights the fault area..

You could try re-installing a fully charged battery and then clearing all codes and see what re-appears..

Have you done any electrical mods to the cat?

Thanks! And this sounds fun..

I put on the new battery and cleared a whole load of codes, and it's just this 3B97 one that won't go away.

Just odd suggestion, is the outside temp. reading correct.
I had to replace my temp. sensor, car did something odd, can't remember what now.

I'll hook up the battery again and have a check!

These cars have several data buses both legacy ones then later ones to support more modern devices..they are then cross tied to allow comms across them..great until something probably quite trivial goes wrong..tricky stuff with out data bus analysers ..let us know what you find out..

Will do, thanks for your input!

[z4lincs]

Zed is booked in to an indy in a couple of weeks but in the meantime I've been trying some diagnosis.

Next to the battery are a bank of large connectors, one with a brown end to it and when this is disconnected the noise stops in the engine bay. What does this send power to? I can't seem to find any answers...

Thanks!!!!

[Pondrew]

Zed is booked in to an indy in a couple of weeks but in the meantime I've been trying some diagnosis.

Next to the battery are a bank of large connectors, one with a brown end to it and when this is disconnected the noise stops in the engine bay. What does this send power to? I can't seem to find any answers...

Thanks!!!!

Brown is usually the earth, or negative. Disconnect that and everything will stop.

[z4lincs]

Zed is booked in to an indy in a couple of weeks but in the meantime I've been trying some diagnosis.

Next to the battery are a bank of large connectors, one with a brown end to it and when this is disconnected the noise stops in the engine bay. What does this send power to? I can't seem to find any answers...

Thanks!!!!

Brown is usually the earth, or negative. Disconnect that and everything will stop.

Ah thank you! Although other bits do stay on, for instance you can lock and unlock the car...

[Pondrew]

Ah thank you! Although other bits do stay on, for instance you can lock and unlock the car...

May be just the earth for that bank of circuits, or even just one. Car wiring colours do seem to be a law unto themselves. In my game brown is always a live, but no so with stupid cars!

[z4lincs]

After taking it for an (unavoidable) drive up to Kendal and back, the problem has somehow stopped and the fault code disappeared! So may be slightly nervous the first few times I leave it, but somehow, it's righted itself