Chevy & GMC Vans

Ok I have a small purple wire that comes out of or goes into the ecm it is not the 02 sensor or the starter wire. I removed the ECM while following the wire and it goes into the larger of the two plugs same as the 02 wire , same color and size but my schematics do not show it at all. If anyone here knows what the other purple wire is for please tell me so I can fix it prior to installing the V8. Thank you, Mark This is an 89 Astro with 4.3 TBI , auto trans with AC and cruise control.

Check the wires on the o2 sensor in the exhaust if there are 3 wires then someone changed the sensor and put in a heated o2. They work better as the early vans ran the sensor a little cold and they fail alot. This could be why the wire doesn't appear on the schematic. If you only have one wire going into the o2 sensor then you still have the stock unit.

Just a guess but hope it helps good luck with the swap.

good thought but I am the one who swapped it to a 3 wire 02 on this van.but thanks for your input. I am guessing since it does not show up on any of the sites it must be either for the cruise control, or maybe something to do with the ac since the van has front and rear ac. I will install my 350 and see if it codes.