Cause of 'Map Controlled Thermostat circuit/control' code?

[kbsilver]

Just about finished with all the mechanical issues with my recently purchased 2000 540iT. When using the Peake reader, I get the 'Map Controlled Thermostat circuit/control' code. I've cleared and and it returns. Car runs fine, heats up in 2 miles, temp guage always dead center even in this summer heat (I know it's center weighted). Checked the themostat and it measures about 12 ohms so its not shorted or burned out. The CEL does not come on.

Any ideas??

Thanks

[victory1auto]

Some E39s have problems with the thermostat heater shorting and taking out part of the wiring harness. Even though yours has not failed yet, you might consider changing out the thermostat/heater, given the code you are getting.

-Vic

[kbsilver]

I understand the preventitive maintenace on the thermostat. But if there is nothing wrong with it now, why am I getting the code?

Thanks.

[RAYADAM]

you are probably getting the code because the DME is looking for a specific engine temp after a given amount of time.the resistance value you have may be good ,but if the T/stat is jamming "mechanically" that will not affect your readings. the thermostat maybe slightly jammed open or closed ,not enough to see the difference on the "dampened" temp guage on the dash.
Vic is right ,you should replace the Thermostat for precautionary measure , overheating the V8 engine can be costly.
one last thing, if your car was built up to 8/99 ,there was a campaign issued for reprogramming the ECU for various O2 sensor faults and 2 FCs for T/stat operation.the ECU needed to be programmed with DIS version 21.0 or later. BMW is currently at V42.1

Ray

[kbsilver]

Ray,

Thanks for the info. The car was built 03/2000 so it sounds as an ECU reprogram is not needed. The only error code I'm getting is this one for MAP cooling. I may try a use the diagnostics mode of the systems display and watch the core temperature. Just flushed and filled the coolant, but guess I can save that if replacing the t-stat.

But all of this will need to wait a few weeks cause I'm dropping it off at the body shop tomorrow (JMK) for some paint work. (Like I said, a fixer-upper!).

Thanks!

[kbsilver]

Thanks all for the advice. Last weekend I changed the waterpump and thermostat. There was no record of the pump being changed so at 75K miles figured it was due.

Although the thermostat looked in perfect condition and electrically tested fine, it obviously was not. After changing, the MAP error has not returned. Car is now DME error free. I even had the t-stat for show-n-tell for the meeting (that wasn't) last night.