"Not Ready"

[ChevyGrl77]

I have a 98 Blazer and just replaced the evap pressure sensor because of my check engine light. We have a code reader so, my boyfriend reset the codes & the light stayed off but, when I tried for inspection, I got a "not ready" on the egr, & evap. How do I get the monitors to reset for these?

[Stealthee]

Basically you have to drive the car. It will have to go through so many drive cycles before it changes to ready.

Things like this makes me glad I live in a non emissions area.

[ChevyGrl77]

The last time I had this issue, I had to drive it over 100 miles before it reset. I was hoping there was some trick to it without having to do that again, considering gas prices have gone up & I can't afford to "just drive around" for no reason.

[Tech II]

No, what you have to do is a COMPLETE DRIVE CYCLE..........

Whenever you clear a code you, you reset all the "flags"......each flag has to run an emission test and pass it, for it to clear.....

If you don't do a COMPLETE cycle, some of the tests won't even run.......

This comes pretty close to what I use to do:

General Motors Driving Cycle
A complete driving cycle should perform diagnostics on all systems. A complete driving cycle can be done in under fifteen minutes.

To perform an OBDII Driving cycle 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. I start the car first thing in the morning so the coolant and air temp sensors should be equal, and close to ambient temp.....I start it right away, and let it idle to normal operating temp, and then I drive it.....

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.

I repeat the accel, steady, and decel tests about 5X's total....