So, I've searched all over and I can't find a similar situation.
When I bought my 02 WRX it didn't nave a cruise control throttle unit (the unit on the passenger side in the engine bay). It also had an 04 steering wheel and an STi cluster. I bought the CC unit and installed it. Cruise control still didn't work. I took off the steering wheel cover and the CC sub switch wasn't connected, well, they weren't compatible. I bought an 02 CC sub switch and installed it into my 04 wheel. I plugged it in... Still doesn't work. The CC button on the lower dash lights up, I'm not throwing any CEL's nor are there any indicators on the cluster that CC has been activated (don't know if their should be).
Any one have ideas? I've checked some fuses but there aren't any CC fuses to check that I can find. Thanks.