1227747 problems

Hi

I am having trouble with my 89 Suburban 5.7L TBI.
I can not get a code 12 ( or any other code ) from the system.

Original ECU blew the ECU-B fuse instantly.
Replaced ECU and got a solid CES light on ignition on.

I have followed chart A-2 all the way down the left side.
I get 5v out of Diagnostic pin (pin B) on ALDL connector.

When I ground Pin B, either to Bin A or another ground point
I get a quick CES light, a short no light, then a solid CES light.

I have replaced ECU with another (3rd) unit with no change in behavior.
It seems unlikely that both replacements... junk yard pulls ... would exhibit same error.

What Now????
Do I need to probe some of the connectors right at the ECU?
Maybe Diagnostic to Ground?

Should I try reading serial Diagnostics from pin E ?
I have not tried as I am assuming that if the check engine light diagnostic is not working then the
serial ALDL data will also be at fault.

Bob

Sounds like you need to make sure the PROM is seated properly in the socked.