[clay4333]

Hi, does the 1990 and 1991 chevy truck and car tbi engine have the same wiring digram. I have a 91 truck harness and computer, having problems incorporating the fuel canister purge motor,which go to a-3 on my computer no pins,on the speed sensor, are the two interchangable ? thanks.

[LATECH]

theyn should be pretty close if not the same. You will have to compare the 2 wiring diagrams for both to be sure.
There can be small differences, like connector design/shape/pin posisition.
a lot of times the connector can be dissasembled and the plastic part can be changed so the alternate style device can be connected to.
As long as you have both harnesses, you should be able to compare them ithout a wiring diagram, and any connector differences should be easy to remedy as you have all you need right there.Otherwise you will hav to make a parts run.

[EagleMark]

They are pretty much the same. The cars usually have IAT or MAT while the truck do not. ECMs usually plug in the same but could be the extra wires for this circut. What ECM nuber did the car have?

The 1990-91 truck uses a 1227747 ECM and all the wiring diagrams for it are here:
http://www.gearhead-efi.com/Fuel-Inj...Information-42