Electrical issues. Not the ignition switch.

[CuyGuyE36]

2003 525i manual transmission

No radio, no turn signal or light indicators on the cluster, no steering wheel controls.

Here's the weird thing. With the key out of the ignition the Hazards will illuminate on the cluster and the radio will work perfectly.

Just replaced the ignition switch today thinking that would surely solve my issue, but here I am.

Anybody have an idea where to look next?

I like this car but I'm about to dump it.

[CuyGuyE36]

https://imgur.com/gallery/vavZfbn

Found these in the compartment where the 6 disk changer goes. The 6 disc changer was not there.

[TiagE39]

As I noted in your other thread, you have a K-bus fault. All of your symptoms are pointing to that.

There are many troubleshooting guides for isolating which one of your modules is causing the fault. I would familiarize yourself with the modules you would encounter on the K-bus on your 525i assuming it is Low cluster.

The simplest way to disconnect K-bus units is at the junction box located behind the glove box.

[CuyGuyE36]

I can't find anything out there for the e39 kbus... I removed the glove box and found a bunch of different wire junctions but have no idea what is what.

[TiagE39]

Follow this guide here. It's written for an E46 but the same steps apply. K-bus junction should be in the connector package behind the glove box.

https://www.bmwgm5.com/K-Bus_Troubleshooting.htm

[CuyGuyE36]

The K Bus block wasn't above the fuse box. It was in the back of the glove box basically on the fire wall... The connections are different too. On the e46 it's a 12 pin connection box I think... So far all I've found is 6 white/red/yellow wires. Not sure if I'm on the right track or not.

[CuyGuyE36]

Checked the white/red/yellow wires as indicated from the e46 kbus thread. No change. I did check my battery and it tested at 11v ... Is a weak battery a possible cause?

[Ed CT]

Yes, a weak battery can cause all sorts of electrical gremlins. Battery should be 12.4+vdc.

Assuming that you checked the battery at rest (engine off). If so, 11vdc is very weak. 11.9 vdc may be able to start the engine, but some non-essential systems may shut down. If you read 11vdc while running, you'll need to start looking at other issues (alternator).

[CuyGuyE36]

Tested the battery again today. It's actually 12.7 so it's pretty good. I'm out of ideas. Might just sell the car.

[TiagE39]

The K Bus block wasn't above the fuse box.

Is your car a high cluster model? (Cluster has OBC message center instead of 4-function trip computer) If so there will also be an I-bus junction box you'll need to test as well.

[CuyGuyE36]

Low cluster.

So far I have changed the ignition switch, checked the kbus wires, checked all of the under seat grounds and power boxes, removed the lcm, radio, and hvac modules individually, and no change.

When I tested the kbus there was one terminal that tested around 8-9 volts and seemed to be a slight drain on the other terminals but removing each terminal did nothing to clear either issue.

The only thing that has gotten rid of my issue, was taking the negative off of the battery for a few hours. That made all of the issues go away, but they returned within two minutes.

I may remove the air bag module just to see if that gives any change. The only other thing I can think of is that I've got a bad aux fan. I am stumped.

[CuyGuyE36]

I should also mention... When I start the car the air bag light goes away for a few seconds and then returns. That's why I suspect it may be causing me issues.

[TiagE39]

I should also mention... When I start the car the air bag light goes away for a few seconds and then returns. That's why I suspect it may be causing me issues.

This is how all BMW's from this era behave when an airbag code is present. The single flash indicates that the power-on self test is complete.

[TiagE39]

Here's the weird thing. With the key out of the ignition the Hazards will illuminate on the cluster and the radio will work perfectly.

Okay, so there has to be a module that uses I/K-bus which is powered down when ignition is in Position 1 but energized when in Position 2. You would need to zoom in on those.