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Unread 08-12-2013, 11:08 AM   #1
crackedcornish
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1988 YJ Wrangler 
 
Join Date: Feb 2012
Location: Lake Hopatcong, NJ
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ECU testing

is there anyway to test the function of an ECU from a '88 2.5L (with TBI) when it's out of the vehicle by using a multimeter?

how do you test the vehicle to know it won't just destroy a new ECU when it gets installed?

when it comes down to this electrical stuff, I have to admit it....I'm lost

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Unread 08-12-2013, 01:12 PM   #2
SeanB95YJ
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if there IS a way, I'd imagine is would require more advanced diagnostic equipment than just a basic multimeter.

do you have a buddy nearby with a similar year 2.5 that you can unplug his ECU and plug your ECU into his/her YJ? see if his YJ runs with YOUR ecu... if it does, and YOUR Yj doesn't start with your ECU then you know the wiring is messed up somewhere.

I'd think to test full function of the ECU, it would require all the usual sensors/inputs normally at the other end of the wiring harness, so would be tough to check (if at all) out of the vehicle.

only possibility I can think of is if you have a Jeep dealer nearby who has been a Jeep dealer for a LONG TIME and may still have some of the older diagnostic equipment available to them.

Good luck
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[FONT="Comic Sans MS"][COLOR="Blue"]Sean B. - Schenectady, NY - 95 YJ, 350/700r4/NP241, JB Shorty SYE, 8.8 rear, 2" BDS, 1" homebrew shackles, Daystar 1" BL, TJ flares, 35x12.50 General Grabber AT2 on 15x10 Bart D-Truckers, Polyshield polycarbonate windshield, HD over/under crossover steering
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Unread 08-12-2013, 04:13 PM   #3
crackedcornish
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OK thanks, I had already planned on parts swapping as a way to troubleshoot it. I was just wondering if anybody knew of any stand alone test that could be run on the ECU while I was waiting .



but meanwhile, this has happened in the last hour...I had taken my ECU out so I could swap around with one of my Jeep club members later this evening.

while I was waiting for him and his Jeep to come over after work, I decided to clean and grease the connection on the ECU. Just on a whim I plugged it back in to give it another try....and Hooray!! the Jeep started!!

I guess it was just a bad connection at the ECU.

the $10 I spent on electrical contact cleaner and a big tube of dielectric grease saved me from buying a $150 ECU, like my Jeep club friends said I would need to do... or the need to swap parts around with another Jeep this evening to troubleshoot it. Needless to say I'm one happy camper tonight
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Unread 08-12-2013, 05:49 PM   #4
Que89YJ
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I would look at the starter solenoid in the firewall and the wires and fuseable links on it. It is the usual culprit for no starts and intermittents. I know you said the problem is gone but if you have the grease clean and grease those wires and terminals too.
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Unread 08-12-2013, 07:45 PM   #5
crackedcornish
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Quote:
Originally Posted by Que89YJ View Post
I would look at the starter solenoid in the firewall and the wires and fuseable links on it. It is the usual culprit for no starts and intermittents. I know you said the problem is gone but if you have the grease clean and grease those wires and terminals too.
thanks for the tip Que...just for the peace of mind after my experience today, I plan to clean and grease all the electrical connections under the hood
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