Engine light won't go off... out of ideas
 

Engine was leaking coolant. Dealership told me it was the thermostat housing. So I bought the thermostat kit and replaced (saving about $1k). So excited that the engine purring again without adding coolant every trip. But then the engine light comes on. So I go down to my local auto parts store to have them tell me why the engine light is on. Cylinders misfiring so I replace all the spark plugs just to be safe. I conduct an code reset but the engine light just won't go! 2010 Coop S R56... any suggestions???

what are the codes popping back?

P0117 - Engine Coolant Temperature Circuit Low
P0128 - Coolant Thermostat (Coolant Temperature Blow Thermostat Regulation Temperature)
P0128 - Program map thermostat: Sticking in open position
P0300 - Cylinder Misfire, Several Cylinders
P0301 - Cylinder 1 Misfire Detected
P0302 - Cylinder 2 Misfire Detected
P0304 - Cylinder 4 Misfire Detected
P112B - Engine Coolant Temperature Sensor 1 Minimum Temperature Implausible
P0173 - which I can’t find but in other forums it mentions “Fuel Trim”

How many miles?

P0117, P0128, P112B - check that you got the electrical connections to the thermostat right. Search here on NAM, there are a lot of threads on thermostat replacement.

Once you get that done and the codes cleared and not coming back, then look at the misfire codes. Since you just replaced the plugs but still have misfires on 3 out of 4 cylinders, probably not the coils. What did the old plugs look like? Might be time for a carbon cleaning.

43k miles on it. I will check the electrical connections definitely. So many wires when changing the thermostat that I thought I labeled them all. I have been using an engine cleaner recently since I can't clean the carbon build up myself and the dealership wants to charge me $800.

You have to check that you got the electrical connections to the thermostat right and the right thermostat with the most current mods.. Something is not right. I have a 2012 and there are 2 different styles of thermostats and 6 different plug configurations.

Aynsniss - Have you made any progress on this? I'm going through a similar problem. 2010 R56s, (manufactured in 2009) 71k miles.

1st REPAIR, $650: Coolant leak. Mechanic replaced thermostat housing (also replaced oil-leaking valve cover gasket, but don't think that is pertinent). Next day, CEL & fan running after car off, regardless of how long engine was on. Mechanic determined it was the wrong thermostat installed. I guess 2010s that rolled off line in 2009 used the old style thermostat.

2nd REPAIR, $0: Replaced thermostat housing again free of charge. Same deal. CEL and fan.

3rd REPAIR, $750: Replaced water pump and friction wheel. CEL again. Codes: P112B and P0117.

Going back in Thursday. I've found two posts elsewhere indicating maybe needs to be re-flashed, but no confirmed resolution. Owned the car for a month now.

I'm assuming that the system was bled properly after replacing the thermostat housing?

My first instinct for misfires is carbon buildup. The N14 engine has a significant problem with that. Some engines are worse than others.

Mike

Did the coolant temp sensor get changed with the thermostat? If not, I'd guess that that was the culprit.