CEL on but can't get any codes!
 

my check engine light came on the other day while i was just driving down the road, i was running very low on gas, so i went and "filled" up (30$) some in each tank, still there, checked coolant fluid level, oil, all good, unhooked battery to clear code, came back on next day, ok.... put some good old sea foam in 'er cleaned out air flow sensor on top of intake manifold, unhooked battery again, back on next day, so i finally stuck it on the scanner, it gets half way through the self test and then quits code P1000 "self test incomplete" tried three times, and its a brand spanking new snap-on scanner so its not the scanners fault, the only problem with the truck is sometimes when i start it up it idles extremely rough and then it either stalls or runs right, anybody got any suggestions?

what motor? you can use a carb cleaner to spray around the intake manifold gasket. possible vacuum leak or iac or fuel pressure leakdown problem and etc. when you did the test did you turn everything off as in the radio, blower motor? and does your truck have obd2 or is it the old ford 1b style? if ford 1b then did you try koeo and koer or just one or the other?

4.9L, think so, obd2, first year for 'em, and both

Does the fuel pump ever continue to run whenever the key is on, and the engine is off?

There's nothing wrong with the scanner.

You need to QUIT disconnecting the battery. Then, the CEL will come on when the computer fails a test and THEN hook up the scanner. Every time you disconnect the battery, it resets the computer, erases the failure code, sets a P1000 status code, and then tries to re-run all the on-board emissions monitors. Since you keep "rebooting", it isn't getting anywhere useful.

FWIW, you likely have either a vacuum leak, a flaky IAC valve, or low fuel pressure based on the operating symptoms you gave.

Steve

we unhook the battery in order to clear the code to see if what we did worked, we only scanned it when the cel came back on, so the computer should've had a code, and on friday i cleaned out mass air sensor and switched to front tank and it hasnt came back on yet. *knock on wood*

Update?

I cleaned the mass air flow sensor out and switched tanks and so far so good. The sensor had like to green dots on it, they came off with 2+2 though