[TDF9]

Driving my 250k mile 2006 325i from Denver home to Boston. Sailing along just fine when Trifecta of lights come on: brake, abs, low tire pressure, all yellow. Uh oh.

Pull off the interstate in Big Spings, Nebraska, just over the colorado line. Get a motel room, come back to the car and it won't crank - starter won't turnover, interior lights dim when I try. As if battery is discharged.

Seems like the cars not charging, and perhaps the ABS / cruise control was just the first system to be impacted? (Although no alternator or battery light or warning.)

Battery is newish, serpentine belt and pulley new and in place (I checked).

I brought tons of tools on my road trip, but of course not a multimeter.

How do I check the alternator? Regulator?

Other things to check?

Weirdly, headlights seemed to be working fine. Only other possible clue is that the gas mileage began to drop considerably over the last 60 miles, from average of 30 to 25. I chocked it up to headwinds or something.

I appreciate any advice! Need to get repaired and back on the road!

[Serf27]

Did you bring a scanner?
Start the car(if you can) and disconnect the battery positive cable to see if the engine stays running or dies.

[TDF9]

Thx for reply. Won't start. Just click and interior lights dim.

No scanner, unfortunately.

[PhaceN52]

Any chance you have/can source an obd scanner?
Maybe check the accessible ground points near the engine and in the trunk for corrosion, but as you said it could be alternator/regulator not charging well the battery, trifecta error could be the result of low voltage.. My car too when the battery was dying throwed any kind of random error.
Tried to jumspart it?

EDIT: was writing when Serf27 asked for scanner too
any way to get one near the motel?
If alternator or voltage regulator went bad they should've triggered codes

[PhaceN52]

try this to check the voltage, enter the secret menu in the dash
(turn off headlights, radio and any other useless thing that drains the battery)
insert key, turn on dash pressing start engine without pressing the clutch/brake pedal (auto or manual?), wait till it stops with the chimes, press the trip reset button right under the gauges and keep it pressed for maybe 20 30 seconds, it should show first the service menu reset, then it should disappear, then it enters a strange menu with written something like 01. fng bla bla (can't remember). Then you push rapidly the button to arrive till point 19, it says lock: on and asks a code , you insert the sum of the last 5 digits of your vin pushing the button (45 is the max obv if you press it one time extra then goes back to 0), and the menu goes back to 01. then you navigate till 09 and it should show the voltage (07 is the coolant temp just for reference lol)

Don't now it it makes sense, but with the voltage live on the dash you can then try to start the engine and check if it drops bad or not, it could point to a jammed starter, but I'm not sure
Did you register the battery with inpa/some diagnostic after replacing it?

[Serf27]

You’re going to need to get it jump started.
Test the alternator by disconnecting your battery cables while the car is on. It might die right after whatever is jump starting it is disconnected.

Sounds like the alternator/voltage regulator went out.
Hopefully it didn’t drag anything else down with it.

[TDF9]

Thank you both! Just awake here, with call into AAA for jump, and will try both ideas!

[TDF9]

Final resolution:

Car mysteriously started this morning, with no warning lights. AAA guy confirmed alternator was putting out 14 volts, so I decided to proceed to North Platte 70 miles away, where I'd (miraculously) found a suitable alternator at an O'Reilly Auto Parts.

40 miles in, symptoms returned - trifecta of lights. I made it to the O'Reillys by the skin of my teeth, with the dash now a full Christmas tree of lights, and the car trying to die.

Changed alternator in the parking lot, got a jump, and the car seems ok (and covered 700 miles today).

Thanks again for all the quick replies and help!

[Serf27]

Nice. Next thing to consider when taking a long trip would be a new starter.

[Tambohamilton]

Earth strap. Check them