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troubleshooting pcm?

DavidinVA

NAXJA Forum User
Location
ashburn, va
okay, i have gathered tons of info from the search already, so any further info would be appreciated!

98 4.0 AW4

engine won't start, cranks, just doesn't fire.
-it's getting fuel pressure to the fuel rail.
-is not getting spark from the coil.
-pulled a code w/ scan tool- indicating code p1694- no output from pcm.
-i'm getting ~5v to the cps and tps.
-instrument cluster is dead. according to my search, that's indicitive of a bad cps, but i checked resistance, and all three wires are indicating an open circuit.

is there any way to check if the pcm is still functioning properly? (it was submerged in water a few weeks ago)

also another strange thing to note that may or may not have anything to do with this. two days ago the truck ran normal. yesterday when i went to start it I noticed that whenever the key is on, the rad fan kicks on. this wasn't happening when the jeep would run. coincidence, or is this telling me something? any suggestions would be great! thanks!
 
sound like your cps i saw a few go bad there is a way to test your pcm you will need a quality d.v.o.m that is computer safe if you use a cheap then ya you'll need a pcm. you need to get a pin out diagram for the pcm, if you can sweet talk it out of your local jeep, dealer if not i think www.alldatadiy.com will sell you a year subscription with all the tests and diagrams.
 
latest developement:

with the key in the 'on' position, i can hear a faint whirring coming from the throttle body/intake manifold area. opening down the throttle and looking into the manifold reveals a manifold full of gasoline. :banghead:
 
does the check engine light illuminate with the key on . if not unplug the cps and see if the dash comes back and the check eng light come back. if so the cps is the prob
 
jneary said:
does the check engine light illuminate with the key on . if not unplug the cps and see if the dash comes back and the check eng light come back. if so the cps is the prob

cluster is dead. unplugging the cps does not change that.
 
i finally found a new cps, and just as i thought. no change.

getting back to my original question, does anyone know how to troubleshoot the pcm? i'm thinking it's gone bad, but i'd like to know something more definitive before i drop the $$ for a new pcm.
 
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