2003 Jeep Grand Cherokee - ABS/Airbag Dash Lights & Bad Gas Mileage
 

Didn't think I'd be posting back here, but I've run into another snafu. One I think I can solve, the other is baffling me.

4.0 6-Cylinder, 2WD, California Emissions Model

When I took my Jeep out of mothball last week, I had removed the battery for preservation reasons; the vehicle had been sitting since April or May. I put this battery back in and attempted to start the vehicle back. The Anti-Theft came on and shut the vehicle off (even after attempting to disable it.) So I reconnected the battery, successfully disable the Anti-Theft and got the vehicle running.

However, the ABS and Airbag lights are on, all the time. OBD shows no errors for these, and the fuses for those systems aren't blown. I'm not sure what I'm missing. Could the Anti-Theft really have caused these issues?

Then issue #2. The Jeep has been eating up gas like crazy. The mileage has effectively been cut in half, and is accurately reflected by the computer on the roof/headboard. I fill it up completely, it shows I only have 220 miles of gas. That's all I will get with regular city driving. The only time I seem to get more gas out of it is when I'm driving on the Interstate above 55. To put this into perspective how bad the mileage is, I put in about 5 gallons of gas from Point A. With "city" driving on slow country roads for about 20 miles, all of that gas is gone.

I do have one error code, P0443 "EVAP System Purge Control Valve "A" Circuit." I'm trying to locate where this is and what it could mean. Sounds electrical so will have to diagnose that; but would that be why I get bad gas mileage, if the actual part is bad and purging extra gas fumes?

Also, what tells the computer how much gas mileage you get? Is it the O2 sensors? I replaced the two downstream ones earlier this year, but that didn't change anything. I have the California model, so I wanted to make sure what would exactly be going on before I dump another $100 on a bunch of sensors.

I already replaced a MAP and pressure sensor already before the summer, those were brand new and replaced.

Any input is appreciated.