What tells the computer when to fire on a TBI w/no crankshaft sensor

K here is the rundown. In the distributor there is a pick-up coil under the plate on the shaft that has two wires and is plugged into the ICM (Ignition Control Module). The ICM is plugged into the coil and back to the ECM. The pick-up coil detects the engine rotation. The ICM takes this signal and uses it to control the spark -> it also sends signal back to the ECM as the RPM input. The computer uses the data for fueling. The ECM sends the spark advance/retard signal back to the ICM for proper spark under the current engine condition. On a side note the ECM will note spray fuel untill it sees ~400 rpm!

You can scan codes and live sensor data from this truck and most other GM OBD1 vehicles with the right equipment. Of course shops and GM scanners can but with a 70 dollar cable and free software anybody can with a laptop. Look-up ALDL cable.

I would change the ICM first. #5 on my '92. Make sure you use the supplied heat sink compound between the module and the baseplate or get some to use. Or it will cook quickly, yes one of the 5.

I have a 94 GMC Sierra and died going down the road running a spark no fuel change the fuel pump change the fuel relay change the filter plugs and wires with all the tune up stuff what else can I do

I’m having a similar issue with my 93 k1500 manual trans... it has no spark no fuel past the injectors... new fuel pump new injectors, cleaned the entire tbi setup with carb cleaner. Brand new distributor, from the shaft to the cap n rotor is all brand new Icm included... I thought the icm was the problem originally but I replaced it before I replaced the distributor to no avail. It has a new map sensor new egr valve new fuel pump and filter... could it be the esc or the ops