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post #1 of (permalink) Old 02-14-2002, 11:13 AM
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Does ECM = MCU ?

I am trying to understand the lingo of some postings and have been confused by the postings vs. text manuals. Is the ECM the Emission Control Unit ? If so , how does it function ? Is the MCU the brain micro processing unit of the computer controlled carburetor feedback systems ? Are these the same or differnet ? Where to locate each in the YJ ?

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post #2 of (permalink) Old 02-14-2002, 12:32 PM
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Re: Does ECM = MCU ?

A horse is still a horse...

I call them the "computer". ECM, PCM, MCU - AFAIK they're the same. Not sure about YJs, but emissions-controlled CJ "computers" are located behind the glove box.

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post #3 of (permalink) Old 02-14-2002, 03:07 PM
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Re: Does ECM = MCU ?

I'm not familiar with "emissions control unit." I think the answer to your question is yes, MCU and ECM are the same. I think ECM stands for engine control management or something close to that.


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post #4 of (permalink) Old 02-14-2002, 03:33 PM
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Re: Does ECM = MCU ?

ECM = Electronic Control Module, the brain.

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post #5 of (permalink) Old 02-14-2002, 03:58 PM
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Re: Does ECM = MCU ?

Taz is correct re: ECM. However, depending on your year jeep, you are going to have more than 1 module. On pre-FI jeeps with the computer controlled carb, you will have the ECM (commonly called the "Computer") that is mounted under the dash (typically on top of the heater duct) and it controls the Carb servo and the other emissions control, i.e., PCV solenoid, etc. Then located on the left fender well is the ignition control module (ICM). This is the standard Motocraft control module for the Duraspark system. Except for one wire, it can run the jeep without the ECM. The one wire is the feed for the coil. The ECM intercepts the signal and delays as necessary to compensate for inputs from the other sensors. The Nutter Bypass is a way of bypassing the computer. I personally don't know if it gains you anything over a properly running setup.

On later fuel injected engines, there is only the ECM or computer which takes all the inputs from sensors and drives the ignition and injectors.

Maybe we should get them to include a glossary for this BBS. Some acronyms have two or three meanings depending on context..i.e., R& it Ring and Pinion, Rack and Pinion or Red and Pink?

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post #6 of (permalink) Old 02-15-2002, 06:54 PM
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Re: Does ECM = MCU ?

Thanks to all who contributed to my education and clarity of the subject. I wish that I had had this understanding long ago . It would have saved me much slow learning.

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