Hooked
We all know how important grounds are in an
electrical system, and when it comes to our trade we can tell
incident after incident of weird, unexplainable transmission
malfunctions that are taking on “fish story”
proportions. And, in fact, we have caught quite a few large
ones over the years.
How about catching a small fish before it
gets too big? You need to be aware of a ground used in Subaru
vehicles with the newer 4AT phase 2 transmission.
In the typical wiring diagram on page 100,
notice that the ground wire for the transmission control module
is inside the transmission.
Figures 1 and 2 show you the location of
this ground. As you can see, it is a typical wire with an
eyelet attachment. This is one vulnerable area, and the other
is in the harness connector (see Figure 3). The No. 16 terminal
in the connector is where this ground wire passes through to
the TCM. It is imperative to pay close attention to this ground
wire, making sure that it has not been compromised in any way.
No doubt this could turn into a big fish
story of TCM crazies causing erratic behavior and a host of
codes. Get it hooked before it gets away! 
©2006 Transmission Digest