New Ride with CEL

[TOMANDPAT]

I just bought another Explorer, a 2000 XLT with a 4.0 OHV 4WD. It's a sweet looking ride, but has a few probs. Among other things, the CEL is on. I checked it last night with my code reader, and got a "0" code. I cleared that, and the light went off. I took it to a shop this morning to get it inspected, and it failed emissions. (It also had some mechanical issues) When I went to the parts store to get the parts I needed the CEL came back on. I had them load test the charging system and we determined my battery was bad. So I got a new battery. Two questions:
1. Has anyone ever seen a "0" code?
2. Would low battery voltage cause the CEL to come on?
Any help would be appreciated. Thanks in advance
Tom

 

[TestPoint]

Low battery voltage can cause all sorts of strange problems.

 

[TOMANDPAT]

Here's an update. It finally threw two codes, P0133 and P0135. Oxygen sensor, bank 1 position 1. I pulled the sensor, tested it and sure enough, the heater was showing high resistance. Replaced the sensor, cleared the codes, but still had a yellow light on the scanner. The scanner was telling me that the Evaporative System was at fault, but not which part, exactly. So I turned to you guys, and started searching. A couple of posts mentioned a brittle o ring on the gas cap, so I looked at mine. NO O RING!! I picked up an o ring at the hardware store, installed it, and rode the highway for about 20 miles. Got home, hooked up the scanner, GREEN LIGHT!! You guys helped me (again) solve my problem. I go back for re-inspection tomorrow
Thanks a million
Tom