1998 955i Speed Triple Ecu Compatibility.!

Hi,

Are you sure its not th sender unit on your radiator thats not faulty...

 

Need the diagnostic fault code to narrow it down. Unless you know for sure it is the ECU itself I would be checking the coolant temperature sensor and the fan relay plus associated wiring and connectors including the connectors to the ECU. The coolant temperature sensor is located under the front of tank near the coolant filler cap and the fan relay should be under the front seat in a bank of 4 second from the left.