The red light ONLY comes on with low fluid or a misadjusted parking brake. The orange (amber) light comes on for thin front pads. So, stepping on the brake will lower the fluid, hense the red light. Yes the main reason for low fluid is thin pads at either the front or the rear. So top of the fluid then inspect all pads.

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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.