how do you know its the computer? -
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Unread 09-25-2009, 04:50 PM   #1
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Join Date: Jun 2009
Location: ky
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how do you know its the computer?

Hello everyone Im back with another question!We have a 97 gjcl that has been nothing but trouble!We recently had it scanned at advance auto and it showed a bad ignition coil.So we changed that plus the gas cap(they said it was vapor locking)and a new throttle position sensor.Well its quit dieing while driving it but now its flooding.Its flashing bad coolant sensor but we just replaced that also.A mechanic that checked it thinks its the computer because the sensor is good.He said its telling the motor its 40 below zero outside!Thats why its sending more gas to the motor than necessary.Anew computer is going to be over three hundred bucks and Im about ready to just roll it over a freaking cliff at this point!Does anyone know how to check for the computer without having to pay a hundred bucks just to find out?Thanks!

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Unread 09-25-2009, 05:14 PM   #2
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ok first of all, never take advise from an auto parts store EVER, next you need to find a new mechanic,

i have run into this instance twice, throwing a coolant sensor code means there is a problem with the coolant temp sensor circuit, it could be the computer, it could be the sensor, it could be THE WIRING IN BETWEEN! also once i got a brand new coolant sensor in the box that was bad, open brand new,

you need to test the NEW sensor, the wiring between the sensor and pcm and if it is still a problem, then i would consider the pcm,

but your right when i senses cool (-40) (open circuit default) it will start pouring the fuel on causing a flood

not only that but unhooking the sensor will put in in open loop

and finally unhooking that particular sensor will put it into base timing mode, making it run like garbage,

you need to find a technician, not a mechanic, someone who actually knows what they are doing and will test it, not just through $300 parts at it to see if it fixes it
-Black Limited 1998 Jeep ZJ 5.2 nv3550 np242, 35s, lots of other stuff
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Unread 09-26-2009, 02:36 AM   #3
Colorado 5.9
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1998 ZJ 
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A bad IAT senser can cause it to run ritch also.
ZJ 98 5.9 LTD. Lots of mods. 7" T&T's Long Arm Lift ,BFG KM2"s,35X12.50x16's,4:56's, Vanco brake upgrade, M1intake,Holley52mmTB,MikeLeach Headers,, Arb'ed HP D30,Aussie Locked rear,Procomp MX6 Shocks,Arb front,RearTR bumpers,ECT.ECT.

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Unread 09-26-2009, 03:17 AM   #4
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1997 ZJ 
Join Date: Dec 2006
Location: , Pennsylvania
Posts: 19,793
You're going to need an fsm to do the diagnostics, as well as a multimeter.
Check the temp sensor for continuity, make sure it reads the right resistance for the temp you have it in. Test it up to operating temps in some hot/boiling water.

Next check the wires for continuity, this is where you'll need the fsm to get the correct pins at the ecu connector.

If that is all good, and the code comes back after a comp reset. You'll need a new ecu most likely.
'97 zj 5.2, some stuff, some other suff, and some things that even work sometimes.

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