You
I have a cat p6000 propane fork lift. It starts but wouldn't run very good, but would run and could be used some.I cleaned the air filter, shut the propane off, unattached then re attached the fuel line from the tank, it ran like a champ for about 10 - 20 minutes then started doing it again but a little worse. Then We noticed it had an e-21 code which is air flow meter error code. I looked it up and saw a video that shows cleaning the air flow sensor (meter) with carb cleaner. I did that reinstalled and it ran worse. like it will start and run until you press the gas pedal, then it will stall or die completely. I went to our local cat dealer and purchased a new sensor installed it and still the same. I've put new air filter, and even tried running it without the filter, but nothing changes.