Suzuki df140 destroying ECM's!!

jrf336

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Dec 19, 2016
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4
Please help ,
I have 2002 df140 it started showing signs of faulty iac valve (hard starting, won't idle) luckily I have another running df140 that I swapped IAC's with. No results. Leading me to believe the ecm is not giving the IAC the signal to operate. So I then swapped ecm's with the other motor and the problem remained , after one attempt at cranking and realizing that the problem was not solved I but the ecm back in the other motor and to my horror the other motor started exhibiting the same symptoms. Some thing in the bad motor appears to be burning up ecm's instantaneously.. at $1500 a pop this is not a good problem to have. Has anyone ever experienced a similar issue?
 

jrf336

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Dec 19, 2016
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Yeah I saw his post but he concluded it was a faulty IAC that shorted out his ecm. Both the iac's I have tried on the motor are working. So where could the short be that is causing the ecm to fail? I'm terrified to buy a new one and put it in place just to have the same thing happen again
 

alldodge

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Wish I could help more but most the OB guys are on Holiday. Make sure to bump this one if you don't get anymore results
 

boscoe99

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Aug 22, 2013
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What appears to be happening between the IAC valve and the ECU is that the ECU grounds a wire to cause the IAC valve to move. If the IAC valve does not move appropriately the ECU will continue to apply the ground, trying to get the IAC valve to respond. After a period of time the ECU will over temp and damage itself.

Many, many Yamaha owner's have replaced a failed ECU without verifying what caused it to fail. Hard to do yes. Anyway, the new ECU can quickly fail, same as the older one. While I hate to throw parts at a problem, before I spent the bucks for a new ECU I might also spend some bucks for a new IAC valve. I would also check the wiring between the ECU and the IAC valve to verify the wires are in good condition. No chaffed wires connecting one to another and no wires shorted to ground.
 

jrf336

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Dec 19, 2016
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Well when I tested the second ecu i had also swapped the working IAC from the motor i borrowed the ecu from so my bad iac could not be the cause for burning up the second ecu. there appears to be nothing wrong with the wiring. I didn't go so far as to meg out all the wires but there is no corrosion or chafing. I'm wondering if there is something else like a sensor or something that could be on the same ground circuit as the IAC that could of shorted out. I have tested the ckp, the cmp and the map sensors, all appear to be working fine.
 

Faztbullet

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Mar 2, 2008
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15,590
Like all EFI engines the ECU has to have a imput to tell the IAC when and how much to move. This is done thru MAP,ECT,IAT and MAF. I don't know what exactly Suzuki uses but it likely one of these triggering ECU to adjust IAC.....
 

99yam40

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Sep 7, 2008
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Well when I tested the second ecu i had also swapped the working IAC from the motor i borrowed the ecu from so my bad iac could not be the cause for burning up the second ecu. there appears to be nothing wrong with the wiring. I didn't go so far as to meg out all the wires but there is no corrosion or chafing. I'm wondering if there is something else like a sensor or something that could be on the same ground circuit as the IAC that could of shorted out. I have tested the ckp, the cmp and the map sensors, all appear to be working fine.

I would check the wiring out completely before ruling it out
 
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