What exactly is the SES light supposed to do when the key is turned from off to run (not start)? Is it supposed to blink once and then stay on steady? Mine just comes on steady. And all kinds of problems I am having. This is on a TPI with a 730 ECM Somebody help, I need you! :hail:

 

As you mention it should come on, blink off for about 1/2 second and then turn on steady. If no blink off then the code isn't running, it's dead.

If a rapid flash then the EPROM checksum failed.

RBob.

 

What would cause the code not to run? The prom and ECM are out of a running vehicle. VATS disabled. Could I have accidentally fied something? It will still flash a code 12, but nothing else.