I have a 1988 735i e32 with 280,000 miles. the instrument cluster started to randomly go to German display and many of the lights started to fail. So I had my mechanic (not a dealer) replace the instrument mother board. He kept the original code plug and everything worked fine for about 20,000 miles. When the mileage reached exactly 300,000 miles, the odometer stopped. The trip odometer still works and everything else works fine. The mechanic tried another mother board but the odometer will not go beyond 300,000.
Is there a way to fix this without taking this car to the dealer? The dealer will probably fix it, but will charge many 100s of dollars.