Found this in the HPTUNERS website...
This is to set the readiness codes to pass, or to help flush out pesky problems.
1. Perform a cold start. ECT must be below 122° also within 11° of the ambient air temperature upon startup. (Note: Do not leave the key in the on position before the start up. This may cause the oxygen sensor heater diagnostic not to run.) Temps are in Fahrenheit for our neighbors to the north.
2. Idle the engine in drive for 2 1/2 minutes with the air conditioner and rear defroster on. You want a lot of electrical load. The more the better. This will run diagnostic tests for O2 heater, Purge "No Flow", Misfire, Passive Air, Fuel Trim and if closed loop is achieved.
3. Accelerate to 55mph at half throttle (1/2). All electrical loads should be minimized. This will run diagnostic tests for Fuel Trim, Misfire, Purge Flow.
4. Steady state cruise at 55mph for 3 minutes. This will run diagnostic tests for O2 response, EGR, Misfire, Air Intrusive, Purge and Fuel Trim.
5. Decelerate from 55mph with foot off the throttle. Do not shift the vehicle manually or touch the brake. Let the vehicle gradually slow itself down to approximately 20mph. This will run diagnostics for Purge, EGR and Fuel Trim.
6. Accelerate to 55-60mph at three quarters (3/4) throttle. This will run diagnostics for Fuel Trim, Misfire, Purge Flow.
7. Steady state cruise at 55-60mph for 5 minutes. This will run diagnostic tests for O2 response, EGR, Misfire, Air Intrusive, Purge and Fuel Trim and catalyst monitor. If you have just reconnected the battery or the cat is only doing part of its job, it may take up to 5 complete cycles for the system to determine the state of the cat.
8. Decelerate with foot off the throttle. This will perform the same diagnostics as in step 5. Do not shift the vehicle manually or touch the brake. Let the vehicle gradually slow itself down to approximately 20mph. This will run diagnostics for Purge, EGR and Fuel Trim.
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