Another way to tell its the cluster screwing up and not actually overheated is the red light on the temperature gauge doesn't come on. The needle pegs out overheated but the light behind the red area of the gauge doesn't light up.

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Just BMW's - All cars and trucks was two pages long
1994 318is
1997 528i
2000 323i
2001 X5 3.0 auto
2005 X5 3.0 auto
2011 535xi auto
2013 X5 xdrive35 Turbo
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Aftermarket E53 Radio Install