try this it works for me everytime. just read carefully.

Instructions to access the hidden OBC functions:
1. Hold Trip Reset while turning ignition key to on position
2. OBC should show "Test"
3. Use Trip Reset to select function 19.0 that unlocks all the features
3. Wait for display to show "Off"
4. Depress Trip Reset for 1/4 second and release it
5. With no delay press Trip Reset several times to select one of the following function s
BMW E46 On-Board Computer (OBC) Hidden Codes
nr example description
1 Car Engine and cluster data
1.0 46nnn Chassis nr/VIN serial number (last 5 digits)
1.1 4nnn K-number
1.2 690236 Cluster Part #
1.3 045210 Coding (04)/diagnosis (52)/bus index (10)
1.4 1200 Week (12)/year of manufacture (2000)
1.5 09_160 Hardware (09) and software # (16.0) of cluster
1.6 Not used
1.7 04__44 CAN-version (04) KI-revision index (44)
2 (test) Cluster System Test - Activates the gauge drivers,
indicators and LEDs to confirm function
3 SI Data
3.0 1098 Used fuel in liters since last SI (Service Inspection)
3.1 0231 Periodic inspection days; elapsed days (since last SI)
4 Momentary Consumption
4.0 0145+ Instant fuel consumption - 0145=14.5 liters/100km
4.1 0018 Instant fuel consumption - 0018=1.8 l/Hour
5 Distance Gone Consumption
5.0 082 Average mileage; 082=8.2 liters/100km
5.1 0536 Calc. km to refuel (momentary distance to go)
6 Fuel Level sensor inputs in liters
6.0 109330+ Fuel level averaged; Left half sensor input=10.9 liters; Right sensor input=33.0 liters
6.1 0439+ Total tank level averaged; vlgs 6.0: 10.9+33.0=43.9 liters
6.2 0442+ Indicated value (44.2) and tank phase
7 Temperature and Speed
7.0 021+ Coolant/Engine temperature (2.1C)
7.1 130 Ambient/Outside temperature - chg met 5 pts. 125/130/135
7.2 + Engine speed / Current RPMs 1/min
7.3 + Vehicle speed / Current Speed in km/hour
8 Input value in HEX form
8.0 1d0+ System voltage ADC-Value Hex code
8.1 26C33C+ ADC Values HG left/HG right
8.2 0000 ADC Value brake degradation sensor (000=o.k.)
8.3 18C ADC Value outside temperature
9 Battery
9.0 140 Battery Voltage - 140 = UB 14.0v
9.1 242013+?
9.2 074_78+?
9.3 0011+?
10 Not used
11 Not used
12 Not used
13 GonG Gong Test
14 Not used
15 Status cluster I/O-ports (bit codes) 0=low; 1=high
1st-belt contact, seat belt fastened=0; 2) ignition lock contact, key inserted=0; 3) door contact, door open=0; 4) clock button pressed=0; 5) SI reset=0, for reset=0; 6) EGS transmission failure=0
Status Digital Outputs (bits) 0=inactive, 1=active
1) Gong output; 2) Brake warning lamp; 3) Low fuel warning lamp; 4) EGA lamp; 5) seat belt lamp; 6) manipulation dot
16 Not used
17 Not used
18 Not used
19 Lock Status; unlocks functions in range 3-18
19.0 L-On/L-Off Unlock: press button when "L-Off"
20 Not used
21 Software Reset; reset OBC settings
00 End of test

^^^^^
 

Thanks alot. The obc works alot better then having to check volt meter.

New battery at stop is 12.4 and with it running I'm at 13.7
With headlights and heater and radio on.

Am I good or do I need an alternator??

Actually I assume I do.

I started to rev the car. And when it goes above 2k rpm the red battery light came on, then goes off below that.

After raving acouple times voltage dropped from 13.7 to 12.7 then I turned lights and heater again and revved and it went to 11.7 volt....

Give me the bad news

if alternator is working, it should be putting out consistent voltage not erratic, should be a steady voltage like around 13.8 v .nothing lower than 13v. (thats with the engine idling or and revved up.

The voltage fluctuation is a classic example of a failing regulator or the lack of contact of the slip rings and the brushes, which in turn drives the regulator to fail.
Volt flux is a sure sign of alt failure that only gets worse. Tests are done at idle, should read over 13.5 volts and again at 2500 which should show an increase to >14.0v.

Quick test, with one eye on the voltage, bring the rpm to 2500 hold, tap the alt with a soft hammer and see what if any change.
At anything over 85k I would remove the alt, while checking for worn or frayed wires. If your plans are long term ownership buy new, if not buy reman AFTER making the seller test the unit before installing. Some remans are slow to break in and provide full output volts/Amps. As mentioned before some models have water cooled others are just air cooled. When you lay underneath your x you will be able to tell.
Good luck.