The Check Engine light came on in my 1996 Ford F250. Took it to the garage. Mechanic told me he replaced the avap sensor but that my truck has two and he can't find the second one. Can anyone explain to me where to locate the evap sensors? Is an evap valve the same thing? Are there really two? Sorry I don't know the error code b/c truck is still in garage. Help! I can't pass my smog with out getting that check engine light turned off. There's no smell of rotten eggs. I really appreciate any help you can give.

Just returned from the garage. The error code is P0443. He gave me a diagram also. The part marked C171 Evap Canister Purge Solenoid isn't where he thinks it should be and he couldn't find it. It looks like it should be next to C182 Delta Pressure Feedback EGR (DPFE) sensor according to this diagram.

I should point out that this truck has passed many smogs. Would it have passed previous smog tests if it was missing? Or would it have had to be in there, but is now broken?

 

P0443 means (if I remember correctly) that the circut to the EVAP control valve has (or has had) an open circut; it's rare, but I've seen it. This is a round valve, usually on the left side of the engine, either right near the master cly. or over a bit more toward the engine.
I would start by looking at the emmissions sticker under the hood; the vacuum lines that go to it will show up on it, so you can at least locate it quickly.
As far as the codes goes, what it means its this: the EVAP control valve has (usually) one vaccum line (not the problem) and an electrical connector on it (with 2 wires). One should be hot when the key is on or key is on and engine running. The PCM looks at the return line (which the pcm swithces) and when turned on, the valve opens. The PCM did not see the voltage it was expecting to see on that return wire.
So, with that wonderful theory lesson behind you, check to see one side has power in the above mentioned states. Also check the connector and wires to make sure that are no obvious problems. Then, you can trace the wire back to the pcm and see if it has continuity.
Hopefully, if it's at the garage, the tech can do a quick key on, eng. off test; if it returns the code here, then it's broken right when the code set (which means its a 'hard' fault).
Also, check to see the valvel itself has continuity. I don't rember the spec, but it should be more then 100 or so ohms. I don't have acces to the ford website anymore (I QUIT!), but I do remember the drill very well.
Good luck!

 

I say greasemark, what do you mean "I quit"? You don't have to answer that if you choose not to! Feel like I've known you for years.

 

Thanks very much, Greasemark. I appreciate you taking the time to help me. Do you by chance know what the part is with two ***** on top? It's right next to the battery.