Low battery voltage to the release solenoid or coffe, coke etc spilled in the shifter area and gummed up the release solenoid. Owners manual should provide instructions to manually release it. Tow truck drivers have to release them manually to tow them sometimes with a dead battery.

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81 300CD (sold) 1972 280 SEL 4.5 (sold) 1966 250 S 4 spd (sold) 1974 450 SL (sold) 86 BMW 325ES (sold), 1973 280C (sold) 1988 300 SE.