Sometimes these trucks will throw an oxygen sensor code if the fuel mixture cannot be regulated. Replacing the oxygen sensor in these cases will not clear the code. You need to check the mixer (carb) for excessive wear, check the idle mixture screw to ensure it is at the correct mixture (need an emissions tester to dial it in), and if the fuel control solenoid switch (a vacuum solenoid that connects engine vacuum to the ambient pressure vent on the vaporiser) is malfunctioning or has a leaking vac. hose, it will also throw this code. Call a technician who has the proper testing equipment and knowledge to do this.

Were are right at the tail end of harvest. I should be able to check it out next week. I'll let you know and thanks for the input.

Did you get that one fixed? Based on the model number, this has the Nikki CARB feedback carburetor system correct? These will turn the MIL on for simple stuff like an open/shorted coolant temp sensor, dead oxygen sensor, base fuel mixture out of whack, etc. There are very few components in the system so it is easy and quick to check. Adjusting the base fuel mixture can be a little tricky but no big deal. I have also seen a lot of dirt and moisture built up in connectors causing various problems on these.

Thanks for the info. I'll check those things out.

No hook ups on a JO2,These are the Pre-computer day trucks.

Check and fill the radiator resevoir bottle, if light stays on disconnect wires to confirm light goes out, most of the time the sensor float in the bottom of the bottle sticks, you can stick a low air pressure blow gun (20-30 psi) into the bottle and give it a couple of quick shots of air and that frees up the float. If not replace the entire bottle assy.

Also check LP tank bracket release micro-switch on top left side of counter weight.