You must have an OBD2 system (1995 approx or later) which includes a self monitoring function. The self test requires that all system monitors complete their cycles successfully to turn the diagnostic code from Red (failed due to current DTC set) to orange (no DTC but drive cycle not yet completed) to green (cycle completed successfully).
Since you were advised to drive for a particular distance, any DTC's had been cleared and the monitor has an orange light (when read by OBD2 reader). However, the advice is not accurate. The driving cycle varies by monitor and many have a 2 trip requirement. A trip usually starts with a cold engine and continues while the engine reaches full temperature and lasts for at least 30 minutes. A second similar trip must be completed for the OBD2 system to record a "green" condition. Your 2 trips are unlikely to start until the engine has cooled off after leaving the shop where you got the advice, probably takes 2 days in reality if no problems.
If in the first trip the system detects a problem it will set a pending DTC and not command the Malfunction Indicator Light (MIL) on. On the send trip if it encounters the same problem it will make the DTC a current problem and command the MIL on.
The evap monitor usually takes the longest to complete a drive cycle and this is at least 30 mins with steady speed highway driving in the last 15 to 20 mins.
Hope this helps.
__________________
Art
2000 Taurus SEL Wagon 3.0 Vulcan (daily driver)
1993 Taurus GL Wagon 3.8 Essex
1991 Mercury Grand Marquis LS 5.0
1986 Chevrolet 3/4 ton pickup 4x4 350 with turbo400 and 208 transfer case
1978 Chevrolet 3/4 ton pickup 4x4 custom 6.2 na diesel with turbo400 and 203 transfer case
Planning 2008 Taurus X in a year
| 
Linear Mode
