Thank you , everyone.

I remembered Elekie's post from years ago but was not aware that some Zetecs, like this one, do not have a separate ECT sensor until I hunted for one in vain...

Serial data shows engine coolant temp. in degrees C and CHT sensor voltage.

I was just concerned that the lean-running condition we were seeing on this engine could be due to too high an engine temperature being seen by the ECU.

The main cause of its lean condition was the common breather valve failure.

Thank you again,

Steve