When we last left our heroes, they were struggling to diagnose a mysterious "Check Engine" light that showed up after the installation of an electronic suspension controller. As I mentioned earlier, I was studying the wiring layout of the car. Had we somehow nicked a ground, causing several sensors to go offline? Was something left unplugged? We went back over all the connectors -- everything was plugged in.
The other weird thing was when the ignition was switched to on, stuff started clicking under the hood. The radiator fan went on and off. I said, "It's almost like it's in pre-delivery test mode." Someone else exclaimed, "The test connector!" I had been looking for that earlier -- turns out it's over in the passenger footwell, not in the driver's footwell like on earlier WRX cars. Well, one of our well-meaning junior mechanics had been putting the interior back together after the suspension install, and seeing a connector unplugged...he plugged it in!
This test mode connector is only intended to be used at the pre-delivery inspection, to make sure all the systems are working. After that it's unplugged. And going back to the wiring diagram, sure enough, the test mode connector plugs into a junction that also attaches to the neutral position switch, which was one of the trouble codes the ECU was telling us about. So we unplugged it on our car, cleared the stored ECU trouble codes, and poof, it's a working car again.
Next up: Dyno testing.