We have to also suggest the BARs advice. Assuming you've
followed the Chevy S10 drive cycle at least twice and are still unable to get the secondary air injection and catalyst monitors to trigger, your best bet is to have the Chevy dealership try to complete the monitors while the truck is on the dynamometer and hooked up to their manufacturer specific scan tool. Via the scan tool they can manually force monitors to run. We'd recommend visiting a smog check repair station, but it might be a hit and miss if they don't have specific experience with Chevy vehicles. If you do find a smog station which is familiar and can set the monitors, it'll probably be much cheaper than the dealership. It won't hurt to call around.
