Ok I have been on here for a little while and have ran across people calling them by different names.

Someone please clarify the exact useage of the PCM and ECM. I thought that the older computers were ECM's but there are guys using that acronym on their third gen's.

If your not sure dont confuse everyone else.


01 cav w/01 3400 gam gt 4t45e

I'm not sure when they changed the name, but it's been PCM for some time now. I guess it had to do with the module controlling the transmission as well as the engine, hence "powertrain control module" instead of "engine control module". But I guess people have used the term ECM or ECU for so long that it's a hard habit to break.

ECM, PCM, ECU, PCU (less common), they all mean the same thing and are interchangable.





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PCM contols the transmission too. Hence the word "Powertrain". Like the 4spd auto j-bodies. The auto Cobalts from what I understand have a seperate module for the trans. So it would be an ECM.

That's how I look at it anyways.

yes.....

PCM = Powertrain Control Module (engine and trans)
ECM = Engine Control Module
ECU = Engine Control Unit



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You know, Thats what I thought too but there are threads that I have seen guys giving advice about the computer and calling it an ecm or ecu where clearly its a PCM that they are referring to. Kind of makes you want to not listen to their advice , doesnt it.
Yeah , I know they are all computers no matter what you call them, but you'd think an advice giver would know what its called.

i saw a few newer cars come in to work and it appears that the computers are getting smaller. Im referring to the ones that are mounted to the firewall. Now are they controlling the engine and tranny from that little thing? I think the cavs with the eco's have what im talking about.


01 cav w/01 3400 gam gt 4t45e

the field of circuit chip manufacturing is getting more percise and smaller by the day, so it only stands to reason that the computer itself will get smaller as time goes on








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