Jeep: Engine Warning Light, flash pause, moderate fee

Question
'01 Wrangler - My engine warning light came on and I suspect that it was do to driving 60+ miles with the gas cap off.  (I did this once before and had the same result, only to have a dealer reset it for a moderate fee)

Is there anyway that I can reset it on my own?

thanx
jim

Answer
Hey Jim,

Unfortunately, no. Although pre-OBDII (On-Board Diagnostics, Generation 2) vehicles could be cleared (before late '95, early '96) by disconnecting the battery for 20 seconds or so, current vehicles require a scantool to clear any DTC's. However, all is not lost...

Any emissions-related DTC (which this is) causes the MIL (Malfunction Indicator Lamp) to illuminate. In order for the lamp to turn off, the computer needs to see 3 consecutive 'Good Trips'. Now, that term has several definitions, depending on the code, but to speed things up a Good Trip for this would be passing the Leak Detection Pump test, which ran and failed twice, originally causing the light to come on. If you secure the cap --if that's the cause-- then the system runs this test 3 times, on 3 consecutive key cycles, and the light will turn off *by itself*. The code will finally clear, in the PCM, after 40 Warm-Up Cycles.

So, if this really is the cause, then it *should* take care of itself. To check codes, you can try turning the ignition switch ON-OFF-ON-OFF-ON and read the display on the instrument cluster. Depending on the year, it will either display the code, or flash the MIL a number of times relative to the code number. For example, FLASH pause FLASH FLASH is code 12. If you get P0441, 442, 443, 455, or 456, then chances are the gas cap was the problem.

Good Luck!