97 cranks but won't start after battery swap, no 5 volts from ECM

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RedTJinArkansas

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Hello, I've seen some other posts regarding similar issues but nothing exactly like my issue.

The Jeep sat for a couple of weeks and the battery was dead. I put a booster on it and it indicated an issue. I then put a charger on it and the battery got super hot. Went ahead and replaced the battery. Jeep now turns over but won't start. After researching I found there is not 5 volts coming from the ECM on the orange wire that goes to the various sensors or the purple wire that goes to the speed sensor in the tranny. I verified that there is 12 volts going into the ECM. After more research it seemed it was either a short in that 5 volt wire or a bad ECM. I've unplugged every sensor according to the wiring diagram. I also don't have any working instruments and don't see any correlation between that and the 5 volt circuit. All fuses are working except fuse 12 behind the glove box. That says panel lamps. I don't recall ever having an issue with this before. I just want to check everything possible before replacing the ECM. Another option I have read about it getting another 5 volt source and connecting it to that circuit. Has anyone done this? Thank you guys for any assistance!
 
RedTJinArkansas said:
Hello, I've seen some other posts regarding similar issues but nothing exactly like my issue.

The Jeep sat for a couple of weeks and the battery was dead. I put a booster on it and it indicated an issue. I then put a charger on it and the battery got super hot. Went ahead and replaced the battery. Jeep now turns over but won't start. After researching I found there is not 5 volts coming from the ECM on the orange wire that goes to the various sensors or the purple wire that goes to the speed sensor in the tranny. I verified that there is 12 volts going into the ECM. After more research it seemed it was either a short in that 5 volt wire or a bad ECM. I've unplugged every sensor according to the wiring diagram. I also don't have any working instruments and don't see any correlation between that and the 5 volt circuit. All fuses are working except fuse 12 behind the glove box. That says panel lamps. I don't recall ever having an issue with this before. I just want to check everything possible before replacing the ECM. Another option I have read about it getting another 5 volt source and connecting it to that circuit. Has anyone done this? Thank you guys for any assistance!
Click to expand...

Also, it's a 4.0 with a 5 speed manual transmission.
 
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According to the Factory Service Manual in the Wiring schematics section; 8W-44-6 identifies the Fuse Block (glove compartment) Fuse 12 feeds the headlight switch interior lighting dimming circuit (instrument cluster illumination, radio, gear selector illumination, a/c & heater controls illumination, rear windshield washer switch and rear defogger switch (if equipped) and fog lamp switch (if equipped).
Once you determine IF the ECM actually has a problem and get the Jeep operating; you may need to troubleshoot the Interior Lighting circuit for an electrical short or bad headlight switch.

https://wranglertjforum.com/attachments/1997-jeep-wrangler-service-manual-pdf.308365/
 
CharlesHS said:
According to the Factory Service Manual in the Wiring schematics section; 8W-44-6 identifies the Fuse Block (glove compartment) Fuse 12 feeds the headlight switch interior lighting dimming circuit (instrument cluster illumination, radio, gear selector illumination, a/c & heater controls illumination, rear windshield washer switch and rear defogger switch (if equipped) and fog lamp switch (if equipped).
Once you determine IF the ECM actually has a problem and get the Jeep operating; you may need to troubleshoot the Interior Lighting circuit for an electrical short or bad headlight switch.

https://wranglertjforum.com/attachments/1997-jeep-wrangler-service-manual-pdf.308365/
Click to expand...

Thanks, once it runs this won't seem too bad.
 
Update, I tested every which way and decided that it had to be the ECM. Then I got a 12volt to 5volt converter and connected it to the 5 volt output from the computer. Fired right up and currently driving it that way. Looking at some cheaper ECM's @ auto parts stores. Wonder if Cardone is any good?
 
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RedTJinArkansas said:
Update, I tested every which way and decided that it had to be the ECM. Then I got a 12volt to 5volt converter and connected it to the 5 volt output from the computer. Fired right up and currently driving it that way. Looking at some cheaper ECM's @ auto parts stores. Wonder if Cardone is any good?
Click to expand...
I don't trust ANYTHING from Cardone. Get your PCM repaired or replaced by forum member @Mark cantrell at www.wranglerfix.com who is the only source of PCMs or PCM repairs I consider trustworthy.
 
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