tutorial for ecu replacement? - JeepForum.com
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post #1 of 4 Old 01-29-2009, 06:47 AM Thread Starter
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Join Date: Jan 2009
Location: MN
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tutorial for ecu replacement?

so my girlfriend bought her grandpas 94 jeep GC recently, it was having problems starting in the last couple weeks. she bought it in florida to drive back to minnesota and the last couple weeks we were there it would take longer to start the colder it got there only on cold starts it was 30-40 deg. when the problem started.

example: turn the key, just cranks. no firing or fuel pump priming, no check engine light at first, but if you left the key in on position the security light would come on then go off, the asd and pump relays click then stop, then the cel would flash as the fuel pump tries to prime, then go off when the relays stopped clicking and the pump finally primed.

other than that runs great for 235k on the clock.

still drove it back with the bad ecu, stopped in georgia the 1st night took 30+ mins the do its electrical spasm then it started.

2nd night stopped in kentucky and it was much colder there and after 45 mins with the key in ON still wouldnt click and the security light never turned off.

i expected that so i brought a extension cord and used a hairdrier blowing hot air on the ecu/ecm and started clicking after 30 sec. and stopped clicking after 15 or more and started right up. didnt stop again after that till we were home

after this i know the ecu is bad soi bought a new one from oreilys, mine was 56029302, got the one that replaces the exact part number.

330 minus 70 core and since theres no returns on electrical stuff i want to make sure i dont mess it up. other than disconnecting the neg battery terminal is there any other DO's or DONT's or can anyone link me to a tutorial?

thanks alot for any help

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post #2 of 4 Old 01-29-2009, 12:38 PM
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2001 XJ Cherokee 
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It's easy. Should only take 10 minutes.

Remove your coolant overflow tank (3 bolts and 2 of them you only have to loosen and slide the tank clips from under them).

Loosen the bolt in the center of the wire terminal. It should pull the terminal apart as it loosens. If it doesn't (like mine) gently pry the terminal out of the ECM with a wide pry bar.

There are 4 or 5 bolts that hold the ECM to the firewall, remove them, remove the ECM and do everything I just said in reverse order.

Hook up battery cable. You're done.

93 Grand Wagoneer
5.5" Hybrid Lift/BDS CA's
231/skids/33" KM2's
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post #3 of 4 Old 01-29-2009, 02:57 PM Thread Starter
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thank you, it looked like an easy job i just wanted to make sure i didnt fry the ecu
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post #4 of 4 Old 01-30-2009, 03:28 PM Thread Starter
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that fixed the problem, she starts right up.
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