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code 41 and code 34

3K views 8 replies 5 participants last post by  ccc 
on our cars it usually wont set a code until it goes into closed loop. if everything is plugged in get a wireing diagram and pin test the harness to the ecm plugs.what i have for a 34 is low signal voltage and to replace the map sensor, and 41 est circuit. i had one once that had the 41 and it turned out to be the module,it had fire and ran but no referance to the ecm. pin test it before you start throwing parts at it
 
you pin test from the ecm plug to what ever sensor or component you are testing. the est is electronic spark timing. i dont think the 83 has an est module on the pass fenderwell so it should be the dist 4 wire plug to the ecm plug.if yours has a knock sensor screwed into the block drain plug just ahead of the starter and a flat module with about 5 wires mounted just behind the overflow tank then you have an est module and would check its wireing to. but you need a wireing diagram to know which pins are which. as old as our cars are getting the wireing becomes suspect when you get circuit codes or low voltage codes
 
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