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ECM Pinout and/or circuit diagram


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#1 OFFLINE   Nate94XE4x2

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Posted 30 August 2010 - 08:08 AM

I have a '94 XE VG30E Auto with an ECM marked MECM-V184. Runs fine. Trying to track down a battery drain, I disconnected the ECM and the stray power draw went away. I cracked it open and found two traces on the board that were smoked, traces that led to each side of a diode marked 'D1'. Upon soldering in a temporary diode replacement and fixing the traces, the battery drain didn't come back... at least, I haven't seen it yet. Runs the same before and after my "fix". Anyone know where I can find circuit diagrams or the pinout for the connector so I can try to figure out what exactly I changed or affected? No error codes showed after I plugged it back in, it flashed a 55 for me... didn't check it before I unplugged and hacked.

While we're at it, does the potentiometer on the ECM do anything besides act as a switch to change the ECM mode? A sticker makes mention of idle speed but not of how it might be used to change it.

Thanks!

#2 OFFLINE   msavides

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Posted 30 August 2010 - 12:24 PM

see this thread

http://www.nissanpat...showtopic=26616

download the FSM

The factory service manual has all the pin-outs of the Ecu in it and what they do. Will also let you know what other use the potentiometer on the ECM does.


Apparently the link now longer works on that page. you can find it using the second link.

or use this link

http://rapidshare.co..._Pathfinder.zip
pass: carpdf.net
Mark

Edited by msavides, 30 August 2010 - 12:29 PM.


#3 OFFLINE   Nate94XE4x2

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Posted 30 August 2010 - 12:59 PM

see this thread

http://www.nissanpat...showtopic=26616

download the FSM

The factory service manual has all the pin-outs of the Ecu in it and what they do. Will also let you know what other use the potentiometer on the ECM does.


Apparently the link now longer works on that page. you can find it using the second link.

or use this link

http://rapidshare.co..._Pathfinder.zip
pass: carpdf.net
Mark


You are a gentleman and a scholar. Thanks!

Edit: Oh wait, I already have that. Guess I need to look closer at it because I didn't find much ECM info the first time through. I don't think any less of you, though :)

Edited by Nate94XE4x2, 30 August 2010 - 01:23 PM.


#4 OFFLINE   Nate94XE4x2

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Posted 01 September 2010 - 07:40 AM

Next questions:

I'm new to the Nissan FSM and I'm having a little trouble following the part relevant to what I found. The burnt traces were on pins 36 and 38 of the ECM. The diagram tells me in one place that those lead into "Joint Connector A" and I haven't been able to find what might be on the other side of that connector. In another place, it makes reference to pin 36 being connected to Ignition switch power and a connection to a "Check Connector"... again at a loss on where to find other info on that connector. Same diagram shows 38 connected to several things, I'm assuming a common ground or something.

Any insight on this?

#5 OFFLINE   msavides

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Posted 09 September 2010 - 07:40 AM

Next questions:

I'm new to the Nissan FSM and I'm having a little trouble following the part relevant to what I found. The burnt traces were on pins 36 and 38 of the ECM. The diagram tells me in one place that those lead into "Joint Connector A" and I haven't been able to find what might be on the other side of that connector. In another place, it makes reference to pin 36 being connected to Ignition switch power and a connection to a "Check Connector"... again at a loss on where to find other info on that connector. Same diagram shows 38 connected to several things, I'm assuming a common ground or something.

Any insight on this?



If you want to make sure everything is working correctly with that part of the ecu.

I would do the diagnostic procedure starting on page 250. Looks like it has something to do with the ignition when starting the truck.


Page 302 explains what pin 36 and 38 do and what voltages they carry at what state the truck is in.

pin 36 goes to ignition switch and should have 11-14v with ignition switch on and 0v with the ignition switch off

pin 38 is the power supply for the ecm. Should have battery voltage when the ignition switch is on.

Hope this helps.

Mark

Edited by msavides, 09 September 2010 - 07:47 AM.


#6 OFFLINE   Nate94XE4x2

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Posted 27 September 2010 - 12:34 PM

If you want to make sure everything is working correctly with that part of the ecu.

I would do the diagnostic procedure starting on page 250. Looks like it has something to do with the ignition when starting the truck.


Page 302 explains what pin 36 and 38 do and what voltages they carry at what state the truck is in.

pin 36 goes to ignition switch and should have 11-14v with ignition switch on and 0v with the ignition switch off

pin 38 is the power supply for the ecm. Should have battery voltage when the ignition switch is on.

Hope this helps.

Mark


Thanks again, Mark... I only just saw that there was another reply on this. I have since surmised that the bad voltage regulator I found last year, the same issue that overcharged and boiled the battery which smelled REEL nice, probably also cremated that trace. I have long since replaced the whole alternator and, since hacking together a fix for the burned trace and diode, I haven't had any more problems with the battery draining. It will be very pleasant this winter not having to plug it into the charger every evening.




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