2005 Mini Cooper S (R52/53-BMW Gen 1)

P0128 Code -- "too long to achieve operating temperature"

When first got call last year -- did laundry list of typical preventative maintenance things: suspension (ball joints/struts/bushings/etc) ... typical oil leaks... serviced supercharger... including REPLACED THERMOSTAT.

But now getting P0128 Code -- reset -- goes away -- comes back in not much time -- troubleshooting so far:

1. Pulled thermostat out and checked it in pot of water on stove -- it opens/closes as should. Stamped with temp 91C - assume that's correct temp for '05 MCS
2. Monitored temp on scanner -- gets up to 215-217F operating temp -- in what appears to be fair amount of time -- not sure how long mini thinks is "too long" to achieve operating temp.

Car is not overheating, etc -- check engine comes on for too slow to temp only -- I realize this is for efficiency goals.

Only other changes on car that I can think off that might even remotely impact coolant temp:

1. Swapped supercharger pulley from my JCW -- so water pump is now running faster -- BUT if thermostat closed -- assume water pump speed would have no impact on taking longer to get to operating temperature.
2. Changed out fan relay with Detroit Tuned Fan Relay KIT -- the one to fix bad diode impacting low speed fan settings. Low speed fan did not come on properly before -- wasn't running with car idle and A/C on.

Anyone have any other ideas to try around resolving P0128?

Thanks
Chris

 

Is it possible the temp sensor is flaky and the temp is fine, just not getting a good signal?