I've read some posts where people have asked how long it takes for an SES code to clear after repairs have been made or to show up after a failure. While I was looking for details on a code, I found this info and I am posting this just for info.


General Motors Driving Cycle for ODBII Code Tests:

To perform a complete OBDII Scan Test on all systems of a GM vehicle, do the following:

Cold Start. In order to be classified as a cold start the engine coolant temperature must be below 50°C (122°F) and within 6°C (11°F) 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 88km/hr (55mph) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.

Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) 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 32km/hr (20 mph). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.

Accelerate. Accelerate at 3/4 throttle until 88-96 km/hr (55-60mph). This will perform the same diagnostics as in step 3.

Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) 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.

Good info.

I have found that sometimes they say drive cycle (I think the above is a drive cycle) and other times they say ignition cycle.

I don't think any cycles are merely turning the car on and off quickly.

I think you'd have to do these tests on a dyno.. there'* no way you'd be able to achieve the requirements for most of those tests on public streets no matter how deserted they are.

It'* what they make a breakdown lane on the highway for.

all the above is described in the FSM where typical scan tool data is shown

And that'* where the information was typed in from Pat.