Chrysler Repair: Chrysler 300M Check Engine Light, obd ii, station assignments

Question
I have a 2001 300m (may be out of you area of experise) that was getting hot.  I figured it was the thermostate, but before I changed it, I removed the Hi Rad Fan relay while the engines was running, reinstalled it and activated the high fan rely mannually.  This did not help, so I went ahead and changed the thermostate.  Sure enough the old thermostate was stuck closed and the new one fixed the problem.  However, I now have a check engine light on and figured it was because of me fooling with the Hi Rad fan rely with the engine running.  Can you tell me how to reset the fault code so the check engine light will go out?

Answer
Hi Mike,
Based on my expeirience with the OBD-I controller that were used thru the mid 90's, I can give you a couple of alternatives. The easiest is to turn on the headlamps, then disconnect the -post of the battery, then turn off the headlamp switch and let the car sit for 5 minutes. Then reattach the -pole of the battery. That will erase the codes, if the OBD-II system has the same feature. (You will have to reset the clock and maybe the memory of radio station assignments, and the 4-speed automatic may take a few days to relearn the characteristics of your powertrain. The other way (which is less intrusive) is to wait it out, because in 50-100 key on-off (off to run position only needed, no need to start the car) cycles it should self-erase, also. Or you can just brute force it by going thru the key on-off cycling now until if gives up and turns off. But before you do anything to erase the codes, why not readout the code and find out if your surmise is correct? Just turn the ignition switch from off to on to off to on to off to on...(in a total time period of 5 seconds or less) and leave it in the on position. Then watch for the check engine light to begin flashing and then pausing and flashing again, etc. Count the number of flashes before each pause, and write the number down. The last set of flashes should have 5 in each. If you look at the numbers you wrote down, you'll see there are an even number of observed groups of flashes, so just group them into pairs of numbers to form two digit numbers, for example the last pair is 5 and 5 or the number 55, which is the code for "end of readout of codes". The code for a fan relay short or open condition is 35 which may be what you get. Also, after you remove the battery from the circuit there will be a code 12 set (without the check engine light) and that too will be erased over time, as described above.
Roland
Let me know how this works.
Roland