Update on no start issue (and PCM questions)

Milrz

Milrz

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Jun 7, 2020
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I wanted to unclutter my previous post and update current situation. You all have been so great and maybe this post will help fix everything.

last week crank no start occurred 02 Jeep4.0 TJ X. Today buddy comes with the snap on scanner and will not read checked plug etc other issue for sure.

so we have no power to the plug that goes to coil pack rail and no fuel. We checked fuel pump there is power but the plug that goes to coil rail no power.

tested pcm only 4v coming out. So questions as follows will pcm going bad allow for obd2 not to read. Should I be checking something else? Replace or reprogram PCM?
 
Daryl said:
The coil rail receives power from the ASD relay in the PDC under the hood for 3 seconds with the key on not cranking. Which PCM connector & pin have 4 volts?
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I watched a video on how to check pcm and where it says 5v I get 4v.

I might be way off here I am gonna do your methods to see.

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The coil rail & fuel injectors both receive power from the ASD relay through fuse 26 in the PDC under the hood.
 
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Daryl said:
The coil rail & fuel injectors both receive power from the ASD relay through fuse 28 in the PDC under the hood.
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We did swap relays around and no change yet. It’s like somehow lost power to spark and no fuel. Do have a good reading at the fuel pump getting power back there. Still probing testing cleaning and checking.

Question I have is when I was taking off oil pressure sensor plug the oil sensor snapped could this of shorted something or caused other areas of concern. I have replaced the sensor and the plug is getting power.

this all started after I took off the plug on the oil pressure sensor and oil sensor broke
 
Milrz said:
We did swap relays around and no change yet. It’s like somehow lost power to spark and no fuel. Do have a good reading at the fuel pump getting power back there. Still probing testing cleaning and checking.

Question I have is when I was taking off oil pressure sensor plug the oil sensor snapped could this of shorted something or caused other areas of concern. I have replaced the sensor and the plug is getting power.

this all started after I took off the plug on the oil pressure sensor and oil sensor broke
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I cannot answer your question with any certainty, anything’s possible. If you follow my instructions, I’ll help you diagnose it. Do you have access to a DVOM or test light? Also, please fill out your profile so everyone will know what year, engine & transmission we’re working with.
 
Daryl said:
I cannot answer your question with any certainty, anything’s possible. If you follow my instructions, I’ll help you diagnose it. Do you have access to a DVOM or test light? Also, please fill out your profile so everyone will know what year, engine & transmission we’re working with.
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I have a test light and ordered a new multi meter it will be here tomorrow. I will fill out more info and follow everything you asked and send pics. Waiting on multi meter for more testing tomorrow buddy took his home.

as a rookie I have to ask what DVOM
 
Daryl said:
I cannot answer your question with any certainty, anything’s possible. If you follow my instructions, I’ll help you diagnose it. Do you have access to a DVOM or test light? Also, please fill out your profile so everyone will know what year, engine & transmission we’re working with.
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This is the one I have coming tomorrow

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That meter will work just fine.
 
Maybe it’s the lighting, but I’d take a battery post brush to the battery & cables again. What’s the deal with that 40amp fuse? It looks like it got hot? The rest of the wiring appears good. I can’t see your G105 at the passenger side engine block, but I’d remove and clean with a brush, then we can get back to testing.
 
Daryl said:
Maybe it’s the lighting, but I’d take a battery post brush to the battery & cables again. What’s the deal with that 40amp fuse? It looks like it got hot? The rest of the wiring appears good. I can’t see your G105 at the passenger side engine block, but I’d remove and clean with a brush, then we can get back to testing.
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Update cleaned the G105 installed new battery cable ends the 40a is new brand new has a blue tint to it. Showing more pics

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What’s your battery voltage? Remove fuse 28 & check it for continuity with your DVOM.
 
Daryl said:
What’s your battery voltage? Remove fuse 28 & check it for continuity with your DVOM.
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I also noticed tonight a ground strap is off the one from firewall to hood is good firewall down is dangling I shoot pic in morning
 
Daryl said:
I’m sorry, I was helping several people at one time & got your year model mixed up with another. Check fuse 9 in your PDC and fuse 12 in your fuse box.
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Will do and let you know how important is that ground strap? Goes to head bolt?
 
Milrz said:
Will do and let you know how important is that ground strap? Goes to head bolt?
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It attaches to the hood. Not important for what we’re doing, but hook it up anyways. Just looking at the wiring diagram and now I have a question for you. Does your Jeep have a SKIM system? It takes a gray programmed key to start the Jeep.
 
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Daryl said:
It attaches to the hood. Not important for what we’re doing, but hook it up anyways. Just looking at the wiring diagram and now I have a question for you. Does your Jeep have a SKIM system? It takes a gray programmed key to start the Jeep.
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Fixed wire ground and I do not believe it’s skim
 
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