I have a 1987 Samurai and have recently had the engine rebuilt. I went to get it smogged and it failed at the upper speed test. Troubleshooting has found the VSV solenoid (Blue/Green wire one not the Blue/Yellow wire) never opens. I checked and the +12V is on the Black/White wire but the 0V never activates on the Blue/Green wire. I understands this comes from the Electronic Control Module (ECM) but before I invest the time and money finding a new one I was wondering what tells the ECM to turn it on that might not be happening?

Any help is appreciated!

The High Altitude Compensator or the fifth gear switch - check your post over at Suzuki Forum.