"BMW X5 - "Check Brake or Rear Lights"

By Ron Stultz

21 May 2010

Summary: only 1 out of 10 times has the problem actually been a bulb. Most often display when extremely moist outside, like rain for days. Problem is connection between bulb holder and rear tail lights assembly. Hassle to fix cause tight quarters but definitely a do-it-yourself (DIY) job.

Background:

BMW X5, 4.4i, model year 2000, 133,700 miles.

"Check brake lights" or "Check rear lights" display.

Tools needed:

- Electrical contact cleaner (sold at home improvement stores and Radio Shack).

- Small needle nose pliers.

To replace brake lights:

You get to brake or rear lamp assemblies (attached to SAV) by removing the access panel on each side.

A connector off the wiring harness connects to the tail light light assembly and provides power to 3 lamp holders via bare metal strips around the holes in the light assembly that are used to hold the lamp holders.

There are 3 plastic lamp holders per side that rotate clockwise into and lock in the light assembly and rotate counterclockwise to unlock and remove from the light assembly.

The 3 lamp holders have "keyed" tabs on them such that they can only lock in place one way.

The 3 plastic lamp holders have metal contacts on them that are bent inward or towards the installed lamp such that when the lamp holders are placed into the hole in the light assembly and rotated to lock, they make contact with the bare metal electrical junction of the light assembly.

Ok, you get a "Check Brake or Rear Light" message and determine which lamp is out by having the car turned on and some one stepping on the brake pedal for you or placing the car into reverse.

You remove the applicable lamp holder, buy a new lamp, install it in the lamp holder and place the lamp holder back into the light assembly.

All is well or well for a while and then you get "Check Brake pr Rear Light" again.

A test reveals that the lamp you just replaced is "out" again.

Lamp holder needs adjustment:

While the design of the lamp-holder-to-light-assembly is mechanically sound, not so much electrically.

In a 12 volt direct current (VDC) system, corrosion at the junction of contacts can disrupt electrical flow and in the case of the brake and rear lights, the junction between the wiring harness connector and light assembly and lamp holders and the light assembly are open to the air and thus damp air can and will corrode the non-copper contacts.

So, whenever you have to replace a brake or rear lamp or if you are getting "Check Brake or Rear Lights":

- Unplug the wiring harness connector from the light assembly.

- Spray contact cleaner onto the contacts of the connector and then onto the contacts of the light assembly.

- Let the contact cleaner dry, evaporate.

- Reconnect the wiring harness connector to the light assembly.

- Remove lamp holder and spray metal contact(s) with electrical contact cleaner.

- Using small needle nose pliers, bend the lamp holder metal contacts toward the lamp.

Now when you reinstall the lamp holder into the light assembly, it may be a little tougher to turn and lock into place but at least you know the electrical junction between the lamp holder and the light assembly is sound.

Finally, should you break the contacts of a lamp holder, simply buy a new lamp holder but use contact cleaner.