Hello everyone. My 2015 s4 is having overheating issues and I cant figure out what’s wrong with it. I changed the thermostat and water pump a few months ago. Last week randomly on the highway the car started overheating and I got a coolant system fault on the dash. Scanned in OBD11 and got “coolant pump malfunction: mechanical error”. (P1B1C00)
Did some forum searching and thought it would be the solenoid on the front ride side of the engine going to the water pump nipple(based off a Ross-tech forum). Changed that and still overheating. Checked the old solenoid and found it still works, checked the black one above the supercharger and that one still works too. Is my water pump defective? I’m running out of ideas as to what it could be. I also thought it might be the auxiliary pump so I purchased a cwa100 but have not yet installed as I believe the stock one is working and didn’t wanna introduce new variables until there’s no other option. Water pump is GRAF oem, thermostat is Mishimoto. Car is stage 2+ with CTS heat exchanger. Very confused and would appreciate any advice.


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