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  #1  
Old August 8th, 2018, 21:31
alsogotanxj alsogotanxj is offline
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cranks, but no start after electrical mess up

Well that was a mistake and now im stumped... I was trying to install a switch for my aux fan using the ground on the relay as some youtube video said. In doing so I fried the electronics in my jeep. I had assumed 85 would be the ground because thats what I saw in all the diagrams. But anyways I connected a wire to 85 and went to touch it to the ground and my fan didn't come on, but I heard clicking from the battery or somewhere near it.

Now my jeep will crank, but not start. Changing batteries hasn't fixed it. Fuses are all good.

My CEL will not turn on at all even on start up, I cant get codes to show on the odometer. It worked earlier today. I even tried to unplug the temp sensor to see if that would change anything, but it didn't. My battery and fuel gauges are also not working.

I tried unplugging the CPS, based on what I read in this thead, but that doesnt help either,

I'll be pulling codes tomorrow when my scanner arrives and Im assuming I fried the computer. What other diagnostic steps should I take?
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Old August 9th, 2018, 04:14
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Tim_MN Tim_MN is offline
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Re: cranks, but no start after electrical mess up

What kinda vehicle ? Year/engine/transmission ?

You checked ALL of the fuses in the fuse box and the Power Distribution Center ? You checked the fusible link in front of the Power Distribution Center ? Since you likely caused a short circuit, problem solving for a bad CPS probably isn't going to work.
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  #3  
Old August 9th, 2018, 12:52
alsogotanxj alsogotanxj is offline
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Re: cranks, but no start after electrical mess up

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Originally Posted by Tim_MN View Post
What kinda vehicle ? Year/engine/transmission ?

You checked ALL of the fuses in the fuse box and the Power Distribution Center ? You checked the fusible link in front of the Power Distribution Center ? Since you likely caused a short circuit, problem solving for a bad CPS probably isn't going to work.
97 with 4.0l and auto.
The fuses and the fusable link going to the pdc are all good.

I figured it wouldnt be the CPS, unless it was a wild coincidence.

The code reader says it cant connect to the computer.

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Old August 9th, 2018, 13:45
RCP Phx RCP Phx is offline
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Re: cranks, but no start after electrical mess up

85 is the power is the fused B+, 86 is the ground thru the PCM. I would recheck the fuses and all connections with a voltmeter. If your confident on what wires you tapped into it should limit what might have happened.
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Old August 9th, 2018, 15:48
alsogotanxj alsogotanxj is offline
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Re: cranks, but no start after electrical mess up

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Originally Posted by RCP Phx View Post
85 is the power is the fused B+, 86 is the ground thru the PCM. I would recheck the fuses and all connections with a voltmeter. If your confident on what wires you tapped into it should limit what might have happened.
I'm certain that it was the 85 wire. Ill see if I can get a meter for to test things out. All I have at the moment is one of those light bulb testers. With it being 85 is there anything I should suspect?
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Old August 9th, 2018, 18:11
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8Mud 8Mud is offline
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Re: cranks, but no start after electrical mess up

The 85 pin is power in from fuse 11 in the PDC, 20 amp fuse. That same fuse powers many critical relays and modules. Likely hot with the ignition in the run position.

Sometimes you have to check those fuses out really well. Ohm test the fuse removed from it's holder. Get a flashlight and look at the contacts in the holder, I mean get close and look hard. Plug the fuse in and check for power on both sides. And lastly swap it out as a test. On occasion those fuses get almost invisible hairline cracks in them.

I doubt you fried any modules or electronics. More likely a fuse or relay or even the holder spade type contacts are faulty. When I say faulty I mean partial meltdown, carbon fouled, a high tit burned onto the contact or the contact got so hot it relaxed and spread open.

How exactly did you get power to the 85 pin, no way with the relay plugged in??? If you just grounded the relay spade type contact in the holder you may have melted the spade type contact.

If you start swapping out components without making sure the relay and fuse is OK you are likely wasting time and money. Don't assume double and triple check the easy stuff first.
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Old August 9th, 2018, 19:37
lawsoncl lawsoncl is offline
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Re: cranks, but no start after electrical mess up

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Originally Posted by 8Mud View Post
If you start swapping out components without making sure the relay and fuse is OK you are likely wasting time and money. Don't assume double and triple check the easy stuff first.

Ditto. Get a cheap multimeter and start measuring where you have voltage. Hope you didn't waste money on a new battery you probably didn't need.
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Old August 10th, 2018, 16:38
alsogotanxj alsogotanxj is offline
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Re: cranks, but no start after electrical mess up

Quote:
Originally Posted by 8Mud View Post
The 85 pin is power in from fuse 11 in the PDC, 20 amp fuse. That same fuse powers many critical relays and modules. Likely hot with the ignition in the run position.

Sometimes you have to check those fuses out really well. Ohm test the fuse removed from it's holder. Get a flashlight and look at the contacts in the holder, I mean get close and look hard. Plug the fuse in and check for power on both sides. And lastly swap it out as a test. On occasion those fuses get almost invisible hairline cracks in them.

I doubt you fried any modules or electronics. More likely a fuse or relay or even the holder spade type contacts are faulty. When I say faulty I mean partial meltdown, carbon fouled, a high tit burned onto the contact or the contact got so hot it relaxed and spread open.

How exactly did you get power to the 85 pin, no way with the relay plugged in??? If you just grounded the relay spade type contact in the holder you may have melted the spade type contact.

If you start swapping out components without making sure the relay and fuse is OK you are likely wasting time and money. Don't assume double and triple check the easy stuff first.
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Originally Posted by lawsoncl View Post
Ditto. Get a cheap multimeter and start measuring where you have voltage. Hope you didn't waste money on a new battery you probably didn't need.
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Old August 10th, 2018, 16:40
alsogotanxj alsogotanxj is offline
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Re: cranks, but no start after electrical mess up

sorry for the weird quoting i had some browser errors.

I havent bought anything besides the multimeter. so I should get things tested tomorrow after work. fuse connections are pretty dull and its hard to tell if theres carbon on them so ill check the connections clean those up and see how things look. thanks for the informative post. I didnt realize that fuse powered so many things.
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  #10  
Old August 11th, 2018, 16:08
alsogotanxj alsogotanxj is offline
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Re: cranks, but no start after electrical mess up

Ok. multimeter came in. The fuses themselves are good, but a couple arent getting power. This includes F24 for the O2 sensor and F21 which powers both the PCM and ignition coil. Heres an image for visual reference

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  #11  
Old August 11th, 2018, 16:44
alsogotanxj alsogotanxj is offline
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Re: cranks, but no start after electrical mess up

Which points to what 8mud said about fuse 11 in the fuse box in the passenger foot well. Sorry I misread the previous post. Got in there and cleaned it and its all good now.
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