How do you replace bulb on turn signal on BMW x5?

TURN OFF THE HEADLIGHTS FIRST. REmove the four 8 mm bolts. Two are on top,and two kind of hidden behind, inside the engine compartment. You have to look for these, and you will need a socket extension. Don't drop them down the back of the engine or anything stupid. On the passenger's side, it is quite easy to disconnect the air intake from the secondary air pump by accident, so check this on reinstall.

Don't pull it all the way out, just far enough to get to the turn signal. LEAVE THE HIGH VOLTAGE STUFF ALONE and hope you never have to fix that. Note the body-colored plastic trim piece slides toward the center of the car (froma tab on the fender), so you have to pull the inside of the headlight out, and then slide toward the center of the car. Be gentle, or you just bought yourself a new $1000 headlight assembly while trying to replace an 89 cent bulb.

Check the socket for corrosion or signs of arc-ing. It only takes a little, as it is a point contact. Here there is telltale black arc'ing burn on the socket (not sure you can see it in this picture or not).

A little fine grain sandpaper will take that corrosion off. Don't go crazy. It is pretty flimsy brittle plastic, so be gentle. BLOW OUT the sanding dust.

To prevent water corrosion or even arc'ing in the future, jam some dielectric grease in the socket. Connectors are one of the highest failure rate items in any electrical circuit. Buy a can and USE IT anywhere on your car there is a connector (make sure the power is off, first!).

After CAREFULLY re-installing the headlights (lots of brittle plastic here, be gentle and don't force anything) we test the lights. Note the spec'd Sylvania is a 3457AK, but in many stores, the 3457 is a clear bulb. Make sure you get the right bulb. NOTE: The "sport package" X5 has clear turn signals which use a yellow bulb. The standard X5 has yellow turn signals that use a clear bulb.