Thank You God! I finally got the truck through inspection!

Primary solution was simply replacing the thermostat. This allowed the engine to run closed loop. This allowed the ECU to collect data during the drive cycle to prepare readiness tests.

But, my truck never fully came ready. The Evaporative System never came up ready. And, when I got inspected, the EGR System was not ready either. I scanned the engine and monitored readiness tests just before taking it in.

I learned how to interpret the test results to determine why a test might not be ready (not all tests completed Pass):
http://service.gm.com/gmspo/mode6/

...that's a very cool site setup by GM for mechanics. You can get OBDMID test details and you can also get Trouble Code details. Very cool.

But, I also learned that the EPA allows vehicles year 2000 and below to go through even with two of the whatever: 8-11 readiness tests not ready. Check that out here:
http://www.obdii.com/articles/OBDII_...s_Testing.html

...this is a great article. Scroll down to the section on READINESS FLAGS and you'll see that up to 2 tests can be down. 2001 and above must have all but one test ready to get through.

So, now that I'm though inspection - I could not possibly care less as to why the EVAP system won't come up. ...at least not for another 2 years ;-)

 

Definitely good links! I use the OBDii.com one every once in awhile and have seen the gmspo before, but never really used it. When I get a chance, I'll add them to the DTC index.

 

Perform a GM OBD-II Driving cycle:

• Cold Start In order to be classified as a cold start the engine coolant temperature must be below 122?F (50?C) and within 11?F (6?C) of the ambient air temperature at startup. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run.
• Idle The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge "No Flow", Misfire and if closed loop is achieved, Fuel Trim.
• Accelerate Turn off the air conditioner and all the other loads and apply half throttle until 55mph (88km/hr) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.
• Hold Steady Speed Hold a steady speed of 55mph (88km/hr) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.
• Decelerate Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 20 mph (32km/hr). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.
• Accelerate Accelerate at 3/4 throttle until 55-60mph (88-96 km/hr). This will perform the same diagnostics as in step 3.
• Hold Steady Speed Hold a steady speed of 55mph (88km/hr) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.
• Decelerate This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears.