Bmw 3 series e46 1999---- fault code 171

SOURCE: BMW 325 TD STARTING FAULT

i have a 1995 bmw 318tds compact that when i try to start it will not turn over i have changed the glow plugs they heat up but there is no power going to them dose anyone no the answer

SOURCE: speedo and abs light on bmw 5 series

I've had the same problem twice on my 1999 528. The problem is your ABS module. (Bosch 5.7 to be exact.) The failure mode is temperature sensitive and shows up after driving. To test this, turn off the car, get a can of freeze spray and cool down the module. Inverting a can of compressed air used for computer cleaning works too. Give it a healthy freeze, then start up the car again. If the lights are out, then you know your problem. 
All sorts of things don't work when the module is bad. Speedo, windshield washers only give you one speed, fuel gauge drifts back and forth, cruise control,  check engine lights, airbag lights .... and so on, you get the picture, basically anything connected to the computer. My new (great) mechanic calls this the BMW christmas tree. 
You can either replace the module with a new one from the dealer, very expensive, or get it rebuilt. There are a number of rebuilders out there, so take your pick. I've used ModuleMaster in the past and they've been great. $300 and works like a charm. Google them to find their web site, and good luck. 
db

SOURCE: bmw e46 electric wing mirror wiring diagram

your mirror control switch has 9 wires.,your drivers door mirror has 5 wires color coded .from your mirror control switch to your drivers siide mirror / 0.5 black .0.5 brown. 0.5 brown. 0.5 black. 0.5 black.
your passenger mirror wires are 0.5 blue/black .0.5 blue/grey. 0.5 blue/white. the passenger mirror has a ground cable 0.5 brown.
the passenger mirror wire 0.5 green/white connects to a 5amp fuse/F25 onto F31 5amp to a wire 0.75 green/yellow.back to the mirror control switch.

SOURCE: xenon headlight problems

there are 3 things that make the xenon in your car work the bulb, an ignitor, and a control module, you know your bulbs are ok so thats good, now you will want to swap the control modules they are a metal box attached to the headlight assembly its roughly 4"x4" you will remove the hheadlight assemblys to get to the module, there are 4 8mm bolts and then it pulls out, it the light follows the control module then thats what you will need if not you will need an ignigtor, as far as the flickering that is moet likely the module going bad, the company that makes this system is AL (automotive lighting) there is an SIB from BMW about this that says under a warr claim both control modules are to be replaced and the bulb of the faulty headlight, however i cant count the number of times i have done all that and still have to replace the ignigtor, If it is the Ign that is alot harder to swap as you have to dis assembly the entire light assembly

SOURCE: BMW E46 fault code P2799 - what does it mean

If is for a 3 series compact (318ti most common) then
P2799 is the intake air tem sensor 2
Which would explain the high idleing. Probably a sensor problem (bmw will charge) a competant mechanic should do it easily.