Tail light Sensor Fault On 1997 328i - United Bimmer Community

**Habanabananas** · 06-13-2010, 04:26 PM

Im having a bit of bother with the OBC displaying a tail light fault even though both tail light are working.

I have replaced the bulbs on both sides and cleaned the terminals with emery paper, but it still displays the fault?

Has anyone else experienced the same problem, and is there an easy solution to the problem?? Im getting sick of resetting the OBC every time I put the lights on.

Thanks for your time

Peter

**David Mc** · 06-16-2010, 06:39 AM

If you mean you are getting a brake light circuit failure message, you can easily fix the problem by replacing the brake pedal switch (a common fault). Otherwise I would be looking at the light switch/dimmer control.

**Habanabananas** · 06-16-2010, 06:54 AM

Thanks Dave

Break light circuit is fine and don't get warning for that...just tail light fail message. Maybe it is something to do with the light switch....tail lights and all other light work fine, just a pain having to press check button on the OBC every time I put the light on.

**David Mc** · 06-16-2010, 07:05 AM

The only other possible causes are incorrect bulb fitted (dual filament where single is required or vice versa) or incorrect bulb rating (volt/wattage). A quick check against the specs in the owners handbook will tell you.

**Habanabananas** · 06-16-2010, 12:37 PM

I have replaced both single and dual filament bulbs on both sides with recommended Bosch bulbs, but still the same. Looks like a trip down to the auto electrician...see if he can find a solution.

Thanks for your time

**DSP543GP** · 07-14-2010, 08:11 AM

Hi!!!
I'm also experiencing the ssame problem, I changed the bulbs even the brake switch. Still getting the annoying brake light fails. Any suggestions please, or is there a way to reset the obc? Pls help guys

**Winter** · 10-02-2010, 04:52 AM

The check control module often becomes a pain in the ass with folks who replace their lights with aftermarket gear. You sound like the alerts just started coming out of the blue, no bulb change was involved. Did you check your wiring harness in the trunk? Something might be loose, or there might be some moisture getting in there.

Quote:

Still getting the annoying brake light fails. Any suggestions please, or is there a way to reset the obc?

There are modifications that can be made to the check control module which essentially just deactivates the warning, but that defeats the whole purpose for having the friggin thing to begin with

Better to find out what the real problem is. If you have a short or something in your wiring it could start blowing stuff out, creating a bigger problem than you already have. Once its beyond your capabilitity to figure out its time to bite the bullit and pay somebody who can solve the problem.

**gc325is** · 10-02-2010, 11:37 AM

Also check the bulb socket itself and in the car light assembly. They do corrode and result in a poor contact.

**David Mc** · 10-02-2010, 04:35 PM

This is very true, the bottom line is that your OBC expects to see a certain resistance across the tail light circuit. If the resistance is substantially higher or lower than the preset, it triggers the warning. With this in mind, all you have to do is consider what factors could introduce changes that cause the resistance to change - burned out bulbs, bulbs of incorrect wattage, dirty trailer connector plugs, corroded bulb sockets or wiring loom connections, faulty brake light switch (which may actually function perfectly) and wet or damaged wiring.