Last year my warning lights came on - VSC, ABS, etc., across bottom of instrument panel. OBD showed code for front O2 sensor. Tried cleaning it with no joy, then finally found that "both" O2 sensors were bad and replaced them.

Fine since then, then a few weeks ago the lights came on again, then went away. After a couple of times, I put the OBD back on it and showed no codes. Lights are on most of the time but gas mileage doesn't appear affected as it was when O2 sensors were bad. That went on for a couple of weeks.

The other day, I fired it up and lights were out. Stayed out for a couple of days, now they're back on again. Locking front end via the button on 4WD lever works fine - can hear it click and the 4 little dash lights function normally, as does using the lower left dash switch to lock transfer case and, again, the 4 little lights and the blinking yellow light seem to function normally.

What should I look for ?? Doesn't seem to be hurting anything, but I like things to be working properly, so I can depend on them to tell me when things "aren't" working properly. I'm also leaving on the big trailer trip in a week or so and want to cover my butt.

The OBD port does not read ABS/TRAC/VSC/AIRBAG codes. Those have to be flashed using a special procedure which I don't know because I have a 2000 which doesn't have TRAC/VSC. If you search on the forum here you should be able to find the procedure.

I'm surprised. It (the OBD) showed the bad 02 sensor last year, but only specified front sensor. Came to find out both were bad, but it took a while and some fussing with it. When the sensors were bad, the mileage drop was noticeable - couldn't go past 2 gas stations in a row. This time around, it seems fairly normal.....just eyeballing it.

Since it's intermittent, check for loose wires / grounds, as well as loose or corroded battery cables, or even a bad battery. I have had a couple of older vehicles with very odd electrical issues - which cleared up when one of the things listed above was fixed.

Are the sensors OEM?

1st try I used an economy sensor and it didn't work too well. Finally gave up and bought the Denso part as recommended on this forum (more $$) and it was fine after that.

Like I said you have to retrieve the VSC/TRAC/ABS/AIRBAG codes differently as those modules do not communicate with the OBD2 port.