Starts, then instantly shuts off with new ECU, but runs with old ECU.

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Aug 26, 2015 | 04:36 PM

Zerocyde

Thread Starter

Junior Member

Joined: Jul 2012

Posts: 43

Likes: 0

Year: 1992

Model: Cherokee

Engine: 4.0l I6

Starts, then instantly shuts off with new ECU, but runs with old ECU.

Trying to figure out why the 92 xj idles fine but wont rev past 2k after I had the tranny out. Figured, maybe when I forgot to unplug the battery and the starter arched to the frame that it blew the ECU so I just got one from the junk yard and it just shuts off INSTANTLY every time it starts. Put the old ecu back in and starts fine. Was there something I was supposed to do when swapping ECUs?

Aug 26, 2015 | 04:59 PM

toasterknight

CF Veteran

Joined: Jan 2015

Posts: 1,508

Likes: 5

From: Oregon Coast

Year: 1999

Model: Cherokee

Engine: 4.0L I6

Starts, then instantly shuts off with new ECU, but runs with old ECU.

Quote:

Originally Posted by Zerocyde

If the old ecu works when you put it back in how is it blown?

Aug 26, 2015 | 07:07 PM

f1oored

Newbie

Joined: Oct 2014

Posts: 21

Likes: 0

From: Ohio

Year: 1999

Model: Cherokee

Engine: 4.0

Just a thought.

What year Jeep was the JY ECU out of? I'm wondering if you got it from a 99-01 with a transponder key.

I have a 99 and when you try to start it without a transponder key it just shuts off automatically. Sounds like that is whats happening. Though I'm not sure if the XJ transponder keys are even tied to the ECU.