Ok, so after a coil/plug, vacuum/breather hose, PCV valve replacement in my DB7 Vantage, the following is occurring:

Ignition ON > All warning lamps lit > All warning lamps go off
Start car
After 5 seconds > CEL On
Scan > Tool says MIL On, but no codes (permanent or pending) are stored
Perform Erase codes > CEL Off
Drive 10/15 miles > all good
Turn car Off
Repeat, same results
Repeat, same results

So, something is being tested, I presume, in those first 5 seconds after starting that must be failing, but without a code, what is it? And how can I not retrieve a code if the CEL is On, or for that matter erasing the codes (that aren't there) resets the CEL.

Any help from you AM pro techs? Anything I could have dome while replacing the coils, plugs, vacuum hoses, breather hoses, PCV valves, check valves that would cause such a baffling mystery? And BTW, the car runs perfectly, so there's nothing (other than the damn CEL) that says something is wrong.

 

Finally was able to retrieve a code using a laptop + software. It was P1409, which was proprietary to AM, which was the reason my Autel couldn't even read it. It is a Ford code, so was easily found on the web...EGR valve solenoid circuit problem.

Knowing what it was, I found that the connector had fallen off the left bank solenoid. Must not have fully seated it when I put everything back together after the coil change, so it fell off after the first test drive. Any way, plugged it in, cleared the CEL, and voila, no more CEL issues!

 

Glad your diligence and troubleshooting efforts were successful!
Thanks for sharing the results...

 

Hate when **** like that happens..glad you got it sorted out. Simple car to fix, but when your not familiarized with them, they can dig you a grave full of hours soaked in