I come up with a code that says signal missing from either the knock sensor or the electronic spark control module (e s c). My chilton book says that from ''88 - '95 the e s c should be located on a bracket near the throttle body and that trucks '96 - 2000 the esc module is built into the ecu which is located under the hood , unlike trucks '88-'95 where the ecu is behind the glove box.
On my 1995 sierra sle 4x4 5.7L extended cab , the esc module is not where the book says . The bracket is there however it is only holding the egr selenoid . I looked at a 1991 truck and the same bracket holds the esc module on one side and the egr selenoid on the other . My truck doesn't even have wires there to plug an esc module in , which leads me to believe that for some reason that year or late in that year the factory relocated it .
I did however replace the knock sensor which is located on the passenger side bottom of the block .
WHERE IS IT ?????????:banghead:

hey does anyone know wherer the electronic spark control module is on a 1994 gmc sierra

According to my manual you don't have one. It appears the distributor unit handles the functions at this time.