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AW-4 Transmission Swap

OK, it is now later in the week and time to identify/locate the physical wires in the TJ's wiring harness that will be interfaced to the AW4 wiring harness.  Assuming you already looked at my wiring list, you should have noticed that some of connections go to various TJ wires to provide +12V, ground, throttle position, brake pedal switch, etc. 

After looking at the various connections that were needed, I opted to tap into the TJ wiring harness near the PCM (Powertrain Control Module).  This is one of those times when a factory service manual is very good to have available.  There is a plethora of information contained in the wiring diagram section. 

One thing I noticed, when reviewing ScottK's write-up, was the difference in the PCM connector designations between his diagrams and mine.  At first, it kind of threw me for a loop and then I realized his pin-out diagrams were that from the XJ service manual while mine were obviously from my TJ manual.  While the signal functions and wire color are the same, the actual connector designators are different between the two vehicles. 



The connectors on my 98 TJ's PCM has three plugs (as all do) and they are different colors; gray, white, and black (shown left to right in the above photo).  In my wiring list, I listed the connector color as this seems less confusing than using the C1, C2, and C3 that they are also known by in the factory service manual (and which conflicts with the designators that ScottK used in his write-up).    Again, this is where having a factory service manual for your year vehicle really pays off. 

Rather than try to chase the wires around the vehicle's wiring harness, I opted to tap into the necessary wiring fairly close to the PCM connectors. 

Note:  Time to disconnect the negative leads from the battery if you have not already done so. 



Here is a picture of the black plug disconnected from the PCM.  As you can see, the pins are numbered, which makes it pretty simple to reference this end of the connection.


I used an ohm meter to positively identify the wire in the harness.  Since my test leads were too large to fit into the connector, I used a paper clip to make contact with the connector pin.  I used another paper clip that had been sharpened to a fine point.  It easily pierced the insulation on the wire I wanted to test.  So with the paper clip inserted into the correct pin on the connector (and the meter lead attached to the paper clip), I located and identified the wire by its color and then checked that by testing it with the ohm meter.  A short (0 ohms) tells me I have located the correct wire in the wiring harness. 



With the wire properly identified, I cut it in half, stripped the ends back about 1/4", and then spliced the new wire into the connection.  I used heat shrink tubing to seal up the new connection.  (Make sure you slide the heat shrink onto the ends of the wires BEFORE you solder them together.) 



Here are the 4 splices made at the base of the gray PCM connector.  Nice and neat, minimal impact on the remaining wires in the harness.  As each splice was completed, I attached a label to the wire indicating the pin that it was connected to.  When all of the splices were complete, and the vehicle wiring harness was re-taped, I was able to identify each wire by the attached label. 


More AW-4 Tranny Swap



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