ECM Relay Problem Solved? Maybe...
 

2001 Honda Accord 4cyl LX..Cranked, but!
Wouldn't start. Green key light didn't come on...so, had key checked.
Key OK.
Had technician from locksmiths check computer, that seems OK, no codes.
So, did some sleuthing online and otherwise, checked fuses (also OK), saw that a relay under the dash may go bad and cause this problem. So, got replacement, installed it, still no start, no key light.

Put the old relay back on...and car started. Now, I COULD just drop the matter, but, I'm too damn curious and suspicious to do that.
Anybody ever seen this before?

The failure of that relay results in the fuel pump not running. So...
Turn the key to RUN but don't immediately continue to START. Listen for the fuel pump to run for 2 seconds while the check-engine light does it's bulb-check. Its not very loud, so turn off the radio, ventilation, etc.

Those relays have a circuit board inside that's prone to the solder joints cracking. So pulling it out & back in may have pushed the cracks together - for now. If you replaced it with a used one it may have the same problem. (Not sure whether "NEW" ones are much different.) People have had a lot of success by opening the case of that relay & re-melting the joints with a soldering iron.

As an old electronics hobbyist, I'm kicking myself for not thinking of what you said in the first place...but big THANKS, I'm keeping the 'new' one, just in case.

Speed up the production line faster & faster until the solder doesn't quite get hot enough to do a good job... You can imagine the result.

Yup, GM is known for that with it's wiper boards, and anti lock brake controllers.:rolleyes: