93-Check engine code 25

After I drive my 93 LS for ten or so minutes, the check engine light comes on. I checked the code, and it is 25. The only explaination I could find online was "IAT Circiut (I'm assuming that means Intake Air Temp.), temperature out of range. Temp excessive causing a misread by the PCM." What is a PCM? I have noticed that the engine hasn't warmed over the 1/4 mark since it began happening although after a few minutes it usually heats to the midway mark on the temperature gage. What can I do to fix this myself?

PCM = powertrain control module, the car's computer.

this code is most of the time caused by a bad connection to the IAT, check it, it is a two-wire sensor near the air filter box.

the temp gauge problem may be a bad thermostat or ECT(engine coolent temp sensor)

Thank you so much! I'll check that today!

Sorry to bother you about this again, but I told my husband what you told me to check. He said he would, but he has no idea where the air filter is either. I tried to search online but I can't find any pictures. Could you let me know where to look for the filter or more information? Thanks so much,
Ashley

if you have a SL or SL1 with a SOHC engine, the airfilter box is between the engine and firewall, and the IAT is somewhere in the tube supplying air from the front of the vehicle.

if you have a SL2 with the DOHC engine the air filter box is between the driver side headlight and battery. the IAT is a few inches to your left, the car's right, in the tube supplying air from behind the other headlight.