The PCM receives the engine coolant temperature status through hardwired circuitry to the engine coolant temperature (ECT) sensor. The instrument cluster receives the engine coolant temperature data from the PCM through the SCP communication network. The instrument cluster microprocessor monitors the engine coolant temperature data received from the PCM and commands the temperature gauge indication with a corresponding movement of the pointer.
At the dealer we would hook up factory scan tool an see what the PCM is seeing for coolant temp . then go into data stream of instrument cluster an see if it is receiving the same data . , Your best bet , take it to a ford dealer . Before you start replacing parts that don't fix the problem .
Is it a 4 cyl or a 6 cyl? Is it showing a code? If so take it to Auto Zone so they can read the code. Try running one tank of premium gas through it and see if that helps. You might also try a full Synthetic oil change at Wal Mart with Mobil one. It is only $44.00.
The battery junction box is under the hood. Hopefully, the fuse box cover will tell you which fuse and relay is which? Your owners manual should have the this info. If no owners manual, check out fleet.ford.com
Click on owners manual link.
The door ajar signal comes from door open warning lamp switches (14018) located in the door jamb. When any door is open, the generic electronic module (GEM) will cause the door ajar warning indicator to be illuminated on theinstrument cluster . The warning indicator will turn off when the warning condition is removed (the door is closed). You could have a bad door ajar switch .A bad seat belt buckle switch and a low washer fluid sensor bad as well . Finding wiring diagrams for these circuits an doing voltage testing Is the proper way to diagnose problems like this . After four different GEM module . The seat belt buckle switch has B+ voltage on one wire , Brown with lite blue stripe . The other wire goes to ground G-300 . When the buckle is closed voltage goes to ground G- 300 . The GEM will see this an turn off the light . You do not have a bad GEM . This is probably what's wrong with the other lights . Find wiring diagrams here http://www.bbbind.com/free_tsb.html
Enter vehicle info. year , make , model engine size . Under system click on body & accessories , under subsyetem click body controls . Hit the search button , click on the blue link . The diagram will show pin # for each of the lights your having problems with. Test voltage AT each pin . if there is voltage , don't know if system voltage or a five volt reference voltage . There is nothing wrong with the GEM . U better find yourself a better mechanic . The Trainer 32 How To Read An Automotive Block Wiring Diagram
ECM Inputs and Outputs Diagnosis You better get your so called mechanic to check out some of these videos . The dealer probably didn't want to mess with it. They can just look at some peoples vehicles an think this won't be worth messing with . They do it at the one I work at .