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Discussion Starter · #1 ·
A few weeks ago I got the stupid "no bus" error on my dash. (The Jeep had been intermittently not starting since I bought it in December. Usually a few tries and it would go, but now it is just dead.) I changed out the Crankshaft positioning sensor and the camshaft positioning sensor and still nothing. I cleaned the grounds going from the back bolt on the valve cover to the frame and hood, the one that on the firewall closer to the computer and checked the ones on the front speakers. After much searching I found this thread here: http://www.wranglerforum.com/f210/easy-way-to-test-your-pcm-418034.html Pin #2 tested ok for 12.13v but pin #22 was only .913v What should I look for, and where? a broken wire along that part of the harness? Damn....I hate electrical problems!! :atomic:

On a side note, one of my fog lights wasn't working so I started to replace them. The one on the passenger side worked fine, but the one on the drivers side would not work at all. I checked the wires for power and they said that they were giving 12v. I swapped the light from the passenger side to the drivers side but it still didn't work. How can I have power and yet no light??
 

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Based on 1999 FSM pin A22 (black connector) on PCM gets -2 volts from batter via fuse 6 which Is a 30 amp

On left side of under hood fuse box 5th up from bottom

That is all that is involved on supply that plus 12 volts
 

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Discussion Starter · #4 ·
Based on 1999 FSM pin A22 (black connector) on PCM gets -2 volts from batter via fuse 6 which Is a 30 amp

On left side of under hood fuse box 5th up from bottom

That is all that is involved on supply that plus 12 volts
So pin #22 should only have 2v and not 12v?
 

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Check fuse first both for burnt fuse and for dirty corroded contacts where it plugs in

All that circuit is is a wire and one fuse
 

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Discussion Starter · #8 ·
Ok.....One more question. My underhood fusebox didn't come with a lid. Which fuse is #6? I drew an arrow on the picture to help us reference.

 

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Discussion Starter · #11 ·
On the 2002 pin a22 at PCM comes thru fuse 9

Still a 30 amp
Yeah, I figured it had to be #9 if it was "2 above the blue one".

I pulled that fuse and the voltage dropped from .913v to almost .003v. I swapped the fuse and it bumped right back up to .913v.

I don't understand how the power gets from the battery to the black connector. It looks like the harness attached to the black connector goes from the computer directly to the fuel injector rail. The grey and white connectors look like they come right from the fuse box under the hood. Unless someone screwed my plugs up?? They go (from passenger side of Jeep) grey, white, black (drivers side.) Is that correct?
 

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The wire is red/white & appears to go from fuse 9 to the ASD relay & to the PCM but through the C-103 (black) connector above the engine before getting to the PCM. You should unplug the connector from the PCM when checking voltage at a-22. With the fuse out it should have 0 volts & with a good fuse, battery voltage. You can also check terminal 30 in the ASD relay socket which should also have battery voltage (also from fuse 9). If you have a good fuse & battery voltage on the input side of the fuse you have a wiring problem between the fuse & PCM. If so, start by lifting the PDC & checking the terminal crimp to the red/white wire from the fuse for corrosion or damage, then the rest of the wire under the PDC. If good, check voltage at that wire at C-103. That should help isolate where you are losing power to a-22.
 

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Discussion Starter · #14 ·
Ok.....I checked for voltage between the #9 fuse and the ASD and it's fine. There is no continuity between the other leg of fuse 9 and the C103 connector. There is continuity between pin a22 and C103. So does the wire go from fuse 9 through connector C103 to a22 or does it go fuse 9 through a22 to connector C103?
 

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Discussion Starter · #15 ·
I am also getting continuity from the bad post on fuse 9 to the body. I had my neck touching the edge of the hood and when I was checking continuity through fuse 9 to a22 I felt a little sting in my neck. Checked fuse 9 to the little bare spot on the hood and sure enough......beeeeeeeeep. Dammit!
 

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From the diagram Digger posted above you can see how the circuit runs. From fuse 9 to C-103 to a-22. You now know that the leg from the fuse to the ASD is good. As stated above, lift the PDC & start checking from the crimp at the fuse & work up to C-103.
 

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Discussion Starter · #17 ·
From the diagram Digger posted above you can see how the circuit runs. From fuse 9 to C-103 to a-22. You now know that the leg from the fuse to the ASD is good. As stated above, lift the PDC & start checking from the crimp at the fuse & work up to C-103.
I think I have found it. I was thrown off because the red/white wire was discolored at the power side of the C103 connector. But it's definitely cut at the back of the connector.
 

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Ok so if put a jumper across from that wire before the brake to the wire going to the PCM pin does that make it run right?
 

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Discussion Starter · #19 ·
Ok so if put a jumper across from that wire before the brake to the wire going to the PCM pin does that make it run right?
I don't know. The battery is out and I have been trying to get that side of the C103 connector apart so I can see how to replace that cut/corroded wire.
 

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For a test just jumper both sides across the connector

The front part of the wiring section in the FSM shows how to take connectors apart

You can view the FSM of you go online to the Morris 4x4 knowledge base web page
 
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