EST Electronic spark control modual

[jeff1953]

1993 GMC sierra 3500 454 auto, where is it and what does it look like, because i've changed the one in the distributor and then it would not start put the old one back in fired right up, still throwing a code the ESC or ESM is bad what ever it is that controls the spark on that thing.

 

[herkyhawki]

I'm sure someone on here will have more info. Here is something I used to set up my boat engine when I rebuilt it. It says Volvo because it's marine, but it is really a GM engine with Delco EST. https://forums.iboats.com/threads/volvo-est-timing-procedure.267126/
I made my own connector for the jumper and it worked fine.

 

[Schurkey]

I thought the EST on 7.4L was in the ECM, not a stand-alone like the small-blocks and V6.

The service manual would tell you.

 

[someotherguy]

In 1993 it should be in the PCM (assuming electronic transmission-equipped.) Specific equipment will vary, for example, a 1992 lighter duty truck with a non-electronic trans (700R4/4L60) would have an external ESC module (square package with single row harness connector) on the bracket along with the EGR solenoid, passenger side of the TBI.

If that 1991/1992 was a heavier truck with the 4L80E I would expect it to be in the PCM and you'd still have that bracket with the space for the ESC but it would be blank other than the EGR solenoid.. but too much time has passed since I laid eyes on that specific configuration.

By 1993 all the automatics were electronic (4L60E comes out for the light duty, where 4L80E had been out since 1991 for 8600lb gvwr and up) so ESC is contained in the PCM.

Standard transmission trucks.. beats me. Wish I had close-up engine bay pics of the 1995 3500HD 7.4/NV4500 and 1994 C1500 5.7/NV4500 I had a while back.

Getting back on track - I'm guessing you are chasing a trouble code? What code # specifically?

Richard