DIY Part 2: Calibrating and/or Re-Coding your new 18 Button OBC to your specific car!
So I have a lot of new information for everyone that is attemtping this DIY that I will add here since installing my own 18 Button OBC.
The little bugger is actually really smart and holds TONS of relevant information about your car. For the 1st week or so I noticed my MPG Consumption was way way off (between 8 MPG per city and 12 MPG for Highway). Also the Range would recognize my fill ups and reset to about 350 to 390 Miles, but quickly decended down to double digits (90 miles) before my fuel guage reached the half way mark.
So I went ahead and unlocked it only to realize I now had a plethora of new information about my car (sadly most of the units in unlock mode is in Kilometers and Liters).
So if you read the long list of what the TEST #s all mean and still felt confused about what to do next, I will break it all down for you.
A. IF YOUR CONSUMPTION AND RANGE VALUE IS OFF DO THIS:
1. Unlock the unit. Google this or Search it-I'm not going to repeat it here.
2. Run Test #5 and write the number you see down. It will be your RANGE to empty in Kilometers based on the two information values stored in the OBC. These are CONSUMPTION RATE and REMAINDER OF FUEL IN TANK. If your Consumption Rate is off then this number will be off as well.
3. Run Test #7 and write the number you see down. It will be your exact FUEL in your gas tank in Liters based on information directly from your Fuel Level Sensors. This number is always correct.
4. Run Test #20 and write the number you see. It should be 1000 or a number close to that value. This is the OBC's default or previously set Correction Factor value.
5. Go to
Find a Car and find your Car, get your New EPA MPG Estimate for Combined MPG (for example a 1995 318i is 18 City-26 Highway and 21 Combined-You will only use the Combined Value) and write number down.
6. Now get out a pencil and a calculator. You will now compute the Correction Factor for your OBC. Basically you will use the actual MPG for your car to change the Value of 1000 that is stored in your OBC.
7. Find your the OBC's incorrect MPG Value; Start by multiplying your Fuel Remaining in your Tank from TEST #7 by 0.26 to get the Fuel in Gallons. Then multiply your Range Value that you got from TEST #4 by 0.62 to get your Range in Miles. Now Divide the Range (miles) by the Fuel left in your tank (gallons) to get your OBC's MPG which should be incorrect. Now divide this MPG by your car's actual MPG-The Combined Value you got from the EPA website. You should get a low number like 0.590 or thereabouts. Now multiply this number by the Correction Factor Value that you got from TEST# 20. The number you end up with is your new Correction Factor Value.
8. Return to TEST #20 and use your 1000/100/10/1 Keys to reset the value to your new Correction Factor Value* that you just calculated. Hit Set/Reset and there you go. Your Range and Consumption should be fixed.
NOTE: If you find that your Correction Factor is not allowing you to input a number less than 750 then your OBC needsto be recoded at the dealership.
B. IF YOU HAD THE 7 BUTTON OBC or YOUR CAR DOES NOT HAVE CHECK CONTROL and YOU GET THE CHECK CONTROL ERROR MESSAGE AT START UP DO THIS:
1. Run TEST #11. You will see EINHEIT 1 [XX]. Whatever code you see in [XX] write it down and store it. It may be a B6 of BC or some combination of letter and number. If your car is a Europe Model change this figure to BC if your car is a USA model change this figure to B7. Hit Set/Reset. Before exiting the TEST hit 1000 or 100 to see the value for EINHEIT 2 [XX]. It should be set to FF or a similar configuration of letters/numbers. Write that down and store it.
2. Exit the TEST and Turn off and the Turn on your car you CHECK Light on the Odometer and Check Control Error messages on your OBC should be gone. The OBC will now be blank at start up (only the time/date section will be on) until you select an option.
3. If the B7 FF/BC FF codes don't work try other configurations of the EINHEIT 1. The configurations either deletes the Check Control Error Message or changes around your units from USA to Euro. I'm not sure about EINHEIT 2, so leave it alone. If you run into problems just restore the original values of EINHEIT 1 and 2 that you wrote down.
OTHER USEFUL TESTS:
TEST #8 will give you your current speed in digits. Only your speed will be in Kilometers.
TEST #9 Will give you Alternators/Battery output voltage at Terminal R. Good to have if you have a bad battery or alternator and don't want to pay a mechanic to test the voltage.