P261A - is there any way to confirm that coolant pump is faulty?

Question

My mechanic checked it manually and said that it's working fine! The diagnostic also shows oxygen sensor problem. Are these related?

Answer 1

One of the main jobs for the ECM is to look for open short and ground the code you have is for the auxillary water pump , This does not come on all the time only when the engine is off and when the cooling is needed, The Pump may be working  manually it is  the ECM that turns this on.check the connection to the auxullary water pump