Will a PCM from a 2003 TJ fit in my 2002?


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toohak

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Unfortunately still no luck. took starter off and it tested fine. I am 100% it is a wiring issue somewhere unless my ignition finally decided to go completely out during this which I doubt.
 
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Wildman

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Unfortunately still no luck. took starter off and it tested fine. I am 100% it is a wiring issue somewhere unless my ignition finally decided to go completely out during this which I doubt.

I'm going to guess it's in the wiring. Wish I could offer more help.
 

Lou

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2002 and earlier used a 3 wire oil pressure sensor. 2003 and on uses a single wire oil pressure switch. If your oil pressure gauge is weird you know what the problem is.
 

Wildman

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Is your jeep auto or manual?
 

Lou

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Take a picture of the wiring harness between the reverse light switch and the 4 pin connector on the main harness above the transmission.
 

Wildman

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Take a picture of the wiring harness between the reverse light switch and the 4 pin connector on the main harness above the transmission.
He'd started off with a PCM from a CCD Jeep and then just got the 2003 PCM. But his Jeep still won't start.
 

Lou

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C154 is the 4 pin connector above the transmission. On an auto, the starter relay receives its ground through the NSS switch. The ground path is from the transmission case, through the switch, through pin 3 at C154, to the relay coil.

On a manual the ground path is from G105. Pins 1 and 3 are jumped together on the Manual reverse light switch pigtail at C154. I am not sure how he wired up the reverse lights but if this jumper wire is missing it will not crank.

Screen Shot 2021-10-05 at 4.43.44 PM.png
 
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toohak

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C154 is the 4 pin connector above the transmission. On an auto, the starter relay receives its ground through the NSS switch. The ground path is from the transmission case, through the switch, through pin 3 at C154, to the relay coil.

On a manual the ground path is from G105. Pins 1 and 3 are jumped together on the Manual reverse light switch pigtail at C154. I am not sure how he wired up the reverse lights but if this jumper wire is missing it will not crank.

View attachment 281646
Hmm, you know I think this is probably my issue. That hadn't really crossed my mind. I was planning on swapping the wiring harness for a 5 speed instead of the auto this weekend.
 
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Lou

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You don’t swap the Wiring harness. You swap a 10” long pigtail.

How did you connect the reverse light switch?
 
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Lou

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This is a manual reverse light switch pigtail. Everything on the harness is identical except this pigtail and having the clutch switch plugged in.

image.jpg
 
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Lou

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You need to find the 4 pin connector that has the red sliding lock. That’s the connector that interfaces the differences between auto and manual.
 
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Lou

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There is a t case position switch on top of the t case, above the front output. That is where that 2 pin connector goes. I know it goes there because the wire colors are black and black/red.
 
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