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ECM vs. PCM vs. ECU?

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Old Feb 6, 2010 | 09:34 AM
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Default ECM vs. PCM vs. ECU?
What are the actual differences between an Engine Control Module, Powertrain Control Module and Engine Control Unit?

Thanks.

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Old Feb 6, 2010 | 09:41 AM
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ECM - engine control module... controls only the engine... so it is also accompanied by a TCM - transmission control module, to control tranny settings... GM went to this separate setup starting around 2005 in certain vehicles, then more widely used in 2006 vehicles, and now is the norm on all new vehicles...

PCM - powertrain control module - a single control module that contains all the settings/programming for BOTH the engine and the transmission...

ECU - engine control unit - just a term that can be used to describe either an ECM or a PCM...
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Old Feb 6, 2010 | 09:46 AM
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Thanks for the breakdown.

Stupid question but is a TCM required if using an ECM and a T56?

Tipsy
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Old Feb 6, 2010 | 09:50 AM
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what vehicle? what engine? which model ECM - i.e. e38, e40, e67, etc etc??
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Old Feb 6, 2010 | 09:56 AM
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Originally Posted by 06MonteSS
what vehicle? what engine? which model ECM - i.e. e38, e40, e67, etc etc??
I'm just in the hypothetical stage right now. Plan to install an LQ4 and a T56 into a Fox body Mustang.

I have no parts yet. Just collecting knowledge.

Tipsy
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Old Feb 6, 2010 | 10:36 AM
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Originally Posted by TipsyMcStagger
Thanks for the breakdown.

Stupid question but is a TCM required if using an ECM and a T56?

Tipsy
No, controller is still called a PCM even on T56 cars.

LS1 autos also use PCM, no TCM.
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Old Feb 6, 2010 | 11:10 AM
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no, you would not need a separate TCM for that tranny setup... just the ECM for the engine....
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Old Feb 6, 2010 | 11:23 AM
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Originally Posted by 06MonteSS
no, you would not need a separate TCM for that tranny setup... just the ECM for the engine....
Okay...thanks. But based on the age of the average LQ4, wouldn't it be a PCM?

I'm just a bit unsure because you wrote previously with regard to ECM's that "GM went to this separate setup starting around 2005 in certain vehicles, then more widely used in 2006 vehicles, and now is the norm on all new vehicles."

I'm not sure if the LQ4 is still in production but if it is, I'd assume the newer engines had an ECM (with a TCM) and the older (pre-2005?) vehicles had PCM's?

Sorry if I'm mincing terms...I'm just trying to gain some clarity.

Tipsy
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Old Feb 6, 2010 | 12:04 PM
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if it's an older Lq4, that used a single PCM, then you'd need to get the tranny parameters in it disabled, since you're pairing it up with a non-stock tranny setup/combo...

if it's a newer lq4, that uses an ECM/TCM combo, then you just need to use the ECM for the engine...
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Old Feb 6, 2010 | 12:07 PM
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Originally Posted by 06MonteSS
if it's an older Lq4, that used a single PCM, then you'd need to get the tranny parameters in it disabled, since you're pairing it up with a non-stock tranny setup/combo...

if it's a newer lq4, that uses an ECM/TCM combo, then you just need to use the ECM for the engine...
Makes perfect sense.

Thanks!

Tipsy
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Old Apr 17, 2010 | 02:09 PM
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so if i have an lq4 in my truck (2004 2500hd lq4 4l80e) it has pcm i believe. ive read some people have use some OE parts that utilize a cable style throttle body. Also i have read that i can tune my pcm to remove all the torque management. i need help understanding all these things and what the best route would be to extract the most power the is being restricted from my lq4.....

Thanks,
Nick
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