Weapon R;
In most states, big cities have emission testing so the check engine light can't be on or have any codes related to emissions, otherwise you will not pass. Several states have a visual check and pass as well. I live in a county that doesn't have emission testing but the adjacent 2 counties around me do! I'm less than a mile from one.
Here's something that a lot of people don't know..........
The Toyota is going to be inspected by the state(same place where they inspect salvage vehicles), so that it can be classified as an alternative fuel vehicle to omit the emission inspections. I already have the forms but the windshield is cracked badly and has to to be changed, and I just hadn't worried with it. This way it can be registered anywhere in the state no inspection. Just because it is getting this doesn't mean anyone can pass this, the car can run and be driven on no gas which gives it the ability to pass. The suburb can't do this as it runs on gas all the time, even if it gets twice the mileage it should.
By the way, the engine light is very useful in the fact that it can tell you if something else is a problem, i,e; trans codes other engine problems, some body codes, so on. Unfortunately I see some costumers that will drive for years with it on and not know why! If it is on check it ! Fix the problem not related to HHO, and go ...........