Pre ‘93 4L80E

[Amsterdamned96]

I was handed down a truck with a plethora of electrical gremlins. I’m currently redoing the wiring harness which was damaged in a fire. I’ve read that prior to 95 the 4L80E didn’t have a crank position sensor? I also can’t find one (engine has been pulled by me) is it perhaps integrated into the started somehow? Most importantly I’m trying to find out what the vertically mounted computer between the brake oil reservoir and relays on the driver side is. In addition to this I’m also asking myself what this aluminium box is?

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[stutaeng]

The crankshaft position sensor started with the '96+ "Vortec" engines. 4.3, 5.0, 5.7 and 7.4.

The 4L80s from inception (91-95) were mated with TBI engines and did not not have a CPS, so that's correct; but that's specific to the engine, not the tranmission.

unfortunately, I know very little on those trucks, but you may be seeing the ECU? Highly recommend a wiring diagram to figure stuff out.

Someone with more knowledge about these trucks please chime in.

 

[TagAllen]

Although I have not seen a box exactly like that going by the wires and plug I would guess it is a esc which is short for electronic spark control. I believe it controls the advance/retard of ignition timing.