My 1996 F150 with OBD2 is failing Arizona emissions due to disabled EVAP system. I did not disable it and don't know how it would have been disabled. There is an EVAP canister present though.

The technician said they have new equipment this year or last year that detects this issue, and he checked my last 6 years of emissions and said the issue has been there for years. Since they didn't have equipment to flag the issue, it always passed.

I bought a scanner and everything is green except EVAP (evaporative system) and HCAT (heated catalyst) are grey which means not enabled.

They don't seem to care about HCAT as this truck does not have them.

How can I enable EVAP? Is this an ECM issue?

The attached pic shows the monitors ready state. They are orange when "not ready" and green when "ready." Grey is "disabled."

image of readiness monitors

  • 2
    Welcome to Motor Vehicle Maintenance & Repair! I'm going to go out on a limb here and suggest you can't enable (or disable for that matter) the EVAP without reprogramming the ECU. TBH, I'd suspect it was never enabled from the factory to be checked through OBD2. 96 is the beginning of OBD2. While the EVAP system is there, there may not have been a check done on it, which means it wouldn't be enabled. If they have "new machines", maybe it isn't programmed to understand not all functions are enabled for all vehicles. Proving it would be the hard part, though. Commented Nov 17, 2021 at 13:35
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    I think Paulster is spot on. Is this new equipment actually testing evap emissions or just reading codes? Time for a phone call? The Arizona Department of Environmental Quality is responsible for the emissions testing program and laws. For more information, contact ADEQ at 877.692.9227 or visit myazcar.com .
    – zipzit
    Commented Nov 17, 2021 at 14:05
  • Yeah, the Evaporative Emissions Control system is simply catching tank vapors, and purging into the air intake when the car runs. It could be entirely passive. In which case it wouldn't have any interaction with the OBD II system and there'd be nothing to indicate (and nothing to pass/fail). I suspect this is a very stupid testing site who doesn't understand what they are looking at and/or can't look in the book to see that this model does not have this feature. ADEQ does not want you modifying emission controls! So you should not be trying to 'fix' this. Commented Nov 20, 2021 at 0:55
  • This seems to be a very technical issue between what Arizona states was a legal emissions status for six years then suddenly not legal (where zero modifications were made) and Ford's emissions control system. Perhaps calling Ford on this issue may clear up what Ford programmed for '96 F150's. Describing your predicament to Ford may reveal more info and help clarify matters related to the evap system.
    – F Dryer
    Commented Nov 20, 2021 at 7:15
  • @zipzit I called the phone number and the system says to take the vehicle to a referee lane for determination. Which is exactly what I did in the first place, and he is the one that told me I have to fix the EVAP status.
    – jim
    Commented Nov 23, 2021 at 15:38

1 Answer 1


As @Paulster2 suspected, there was no issue. Just to show effort, I did replace some dry hoses and the purge valve, which had no effect on the OBD readings. I took it back to the referee and there was a different person working that day. He said that some early vehicles around 1996-2000 or so have an EVAP system, but the ECM does not implement any checks, and it was not an issue. So, it passed with essentially no changes from the previous attempt. (readings were identical to the attached image in the question above)

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