It's possible. The auxilary pump is operated by the PBU to help circulate coolant through the heat core under low flow conditions (like at idle). The 124 PBUs have an overcurrent limiter in them to prevent the board from getting fried if the pump shorts out. 123s had no protection and many PBUs got fried from a bad pump.

If you remove the windshield washer tank (suck out most of the fluid with a baster, unclip the pumps, lift straight up) you will see 2 heater hoses going down below where the tank was. There is a small pump about the size of your fist. Follow the electrical lead to a 2-pin connector and unplug it. Since it's summer you don't need it right now and it will remove the load from the controller to see if that's the problem.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech