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98 won’t start

cemeyer

NAXJA Forum User
Location
CO
After a suggestion of starting my own thread, I’ll repost here.
I hope maybe one of you guys can point me in the right direction. My 98, 4.0, AW4, had a dead battery, I jump started it the other day to move it up into the garage to replace the badly cracked APN header. Before I Started the header swap, I stuck the charger on it, turned the charger to high amp for engine start, it did not start. It cranks, but will not fire. The fuel gauge doesn’t register, the volt gauge reads nothing, the ASD relay and the fuel pump relay do not pull in. All fuses check good. I pulled a cover off a relay, stuck it in fuel pump slot, tripped it, fuel pump does run. I unplugged the CPS, the one on the fly wheel, it did not change anything. The CPS ohm’s open. I have unhooked all sensors. I have power to PCM. I have no 5V output. I cannot get the code scanner to connect to PCM. Where should I look next? Could I have fried the ECM, when I turned the charger to boost or when I ran it on a dead battery after I jump started it?
Thanks in advance for your help!
 
Grounds at pcm all check out good. From pcm to battery, pcm to body and pcm to engine block.
 
Have you tried another battery, or do you know for certain this one is good?
If A4 has ground and A17 hasn't any voltage at all, I'm a bit inclined to lean towards the pcm. your voltage gauge not reading anything is a bit suspicious as the pcm should still read this if it were a sensor, No?
Do you have access to a working pcm?
 
The battery actually took a charge and passed a load test with my tester. I’ve maintained 12+ volts throughout my testing so far. A4 has ground, A17 has no 5V. I don’t have another pcm to try. My understanding that if a sensor is shorted, it could cause the 5V signal to drop out. I think I’ve pretty much rules out a sensor short, could be in the harness I guess. I’ll do some more testing with my meter to see if I can determine that.
 
Yes as you said you've disconnected all sensors. You've verified ground to the pcm on plug A and there is no 5v out on plug A.
On plug B there's another 5v out you could check (B31).
 
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