Question about some DME Errors 2EF4 / 2F09

[garrett.fell]

So - I let the wife drive the X for the first time in about a year, and she brings it back to me with the CEL light on. It hasn't been on in nearly a year. I run DIS and it comes back with the 2EF4 (map thermostat stuck) and 2F09 (air intake temp)

I try and run the follow-up diag routine and it just come back with a "Fault" message (error number 800.11 - with some other codes) Not sure if that's the resulting fault-code, or if it's telling me it can't run the diagnostics.....

My generic OBD reader translated this into a p-code which basically suggested the coolant didn't warm up within a specified/expected time. I've seen this error before on this car - it would throw it MAYBE once a year usually right when there was a sudden drop in temperature / change in the weather. That might be coincidence but it seems to be the pattern. (maybe it's looking at a rolling average of warm-up times and sudden temp changes mess that up?)

So, I did a little research on this and some hits have suggested the thermostat is at fault and should probably be changed (other hits were suggesting something wrong with the wiring harness? That one doesn't seem likely to me)

My question is this - is the thermostat error a "hard error" (meaning it can tell it's messed up by directly observing it) or is this one of those things which are inferred by reading a bunch of other variables and saying "well it must be this - because I see all these other things".

The car seems to warm up relatively quickly for a big V8 cooling system, the temp-needle always reads straight-up. I did try and do a smooth idle test the other day (to compare readings before/after I ran a bottle of redline fuel injection cleaner through it) but was unable to get the temp above 100 C (it was running in the 90-93 range after a bit of driving, then coming back to the house) so i was not able to meet some of the thresholds for the test to run.....

Anyway - car has 111k miles. The water pump was changed out at some point before 73k when I took possession of the car nearly 4 years ago.

[garrett.fell]

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[upallnight]

Water pump was changed, but did they also replaced the thermostat?

[garrett.fell]

I cannot be sure what was replaced exactly. The indicator I got that the water-pump was changed is as follows:

1. Water stain on sound dampening material on the underside of the hood above the water pump area.

2. The water pump "patina" is different than the surrounding material. It's much less oxidized, much cleaner, etc. I first noticed this maybe 3 years ago and came to this conclusion then.

So although I cannot confirm it was replaced with a work-order the evidence suggests it was at some point prior to my ownership. Whether or not that replacement included the thermostat is a mystery.


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