Car failed On-Board Diagnostic test, what to do?

Question

My wife had me to take her 1998 Ford Taurus to get an inspection sticker in North Carolina. New NC State laws require some cars be given an OBDII test if check engine light is on. The car failed the test with a trouble code PO125 which is Insufficient Coolant Temperature for Closed Loop Fuel Control. A while back the heater core apparently went out on it because there was coolant all in the floor on the passenger-side and the heater would only blow out cold air when the heat was on. We by-passed the heater core and I did replace the thermostat on it. Can you give me any advice of what to do without it costing me an arm and a leg to repair it? We have 30 days to repair it or we will have to pay for another inspection.

Answer 1

Have you been paying attention to the temperature gauge? Has it been acting normal?
The PCM wants to see that there has been a rise in temperature of the coolant commensurate with the time the engine has been running. If the time and temperature don't meet expected values, the PCM watches it, and if it occurs again, it will trigger this code. The PCM needs to know exactly how warm the engine really is for proper fuel and ignition control for power train management. The "Closed Loop" condition is when the PCM is watching the oxygen sensor for information concerning fuel mixture. If the "Closed Loop" condition is met, and temperature is in expected range, the engine performs well, mileage is optimal and emissions are at the lowest.
What to do-----
If indeed the thermostat was changed, was the correct temperature range used. The PCM expects the engine to be somewhere around 195° to 220° F at all times. If you installed a "cool" or a "summer" thermostat, replace it with a 195° unit.
After the repairs, clear the code(s). This will clear the Monitors as well, and this will cause you to fail the test as well. There is an OBD II drive cycle that you can follow (GO HERE)---------->

http://www.obd-codes.com/trouble_codes/gm/gm-obd-driving-cycle.php

...to expedite the running of the monitors.
If this procedure is too complex or you simply don't want to deal with that part, make it a point to drive the car >300 miles under all the NORMAL conditions available, including stop and go, moderate traffic at 35 - 55 mph, and some freeway with the cruise control to allow the PCM to "see" what all the systems on the car are doing.
Remember, when the drive cycle wants a COLD start, it must be cold. The PCM wants to see a coolant temp rise of > 60° F before it will begin to run the monitors.

Good Luck