Mil Specs won't reset on 2000 Montana

[electro452]

I have a 2000 Pontiac Montana that i just took in for smog. It passed emissions but not the MIL check. Here's the diagonstics from the printout."THis vehicle failed the MIL/check engine light due to failure to successfully complete all OBD tests. Fault code P1404." The shop checked for the cause of the 1404 code and found a platic tube about 1/2 " in diameter, that is located between the mass flow sensor and throttle body, had come out from the rear of the manifold. THe codes were reset and I was told to drive for 100 miles and bring it back for a recheck. Drove over 100 miles, brought back for recheck and now the code is not reappearing but the same type message still came up. "This vehicle failed the MIL/check engine light due to failure to successfully complete all OBD tests". The mechanic informed me the vehice computer should have rest in the 100 miles to take it the dealer and have the computer looked at. The Chevrolet dealer told me the computer hould have rest in 20 to 30 miles and the computer may need reflashed. Has anyone else every experienced this issue or can anyone offer any advice on what I should do to minimize the dealer cost of repairs. Could the computer be bad or just need reflashed as they stated? When the code was cleared could the shop have done any damage to the computer?

[electro452]

Well i took the vehicle to the Chevrolet dealer for some help on this issue. Theytold me three of the MIL specs weren't registering after driving the car for about 20 miles. They suggested drving a few more days. Is there a minimum number of miles or start and stops for getting the computer to report? Is there a provedure for getting the computer to relearn. Any help would be appreciated.

[rkvons]

I'n not an expert by any means, but I was under the impression that it was not the mileage that allowed the computer to learn, but rather, the number of times the engine system went through a heat up and cool down cycle. So if you drove 10 miles to work everyday, you would go through 2 cycles per day. Even going to the store to shop for an hour will do it. I thought you needed to go through 30 before stuff clears and things get learned.

['97ventureowner]

When NY started doing stricter emission testing a few years back, some mechanics reported it took up to 300 miles sometimes to get the computer ready to retest again after being reset.We had a number of customers who weren't familiar with the system and thought if they cleared the codes or disconnected the battery shortly before going into the test, that they would pass. They would fail the test and it would tel them that their vehicle wasn't ready and they needed to drive the vehicle more so their computer could go through it's process to test itself and register any codes. I seem to remember seeing a note from Albany ( our state capital where the main DMV is,) stating that in some extreme cases the customer should drive the vehicle at various speeds for up to 300 miles to make sure the vehicle's computer was able to go through all of it's functions.
Maybe you need to drive the vehicle more to get the results you need.

[electro452]

Thanks for all the replies. To make a long story short the smog tech was giving me bad information. I'm located in Ca and we have some pretty strict smog laws. Here's what I've learned.

Every OBDII generation car has two sets of monitors. Continous and non continous. The continous monitors should be "ready" all the time regarless if the vehicle has been through a drive cycle for learning purposes. These continous monitors are:

Misfire (continuous)
Fuel Trim (continuous)
Comprehensive Components (continuous

Non continous monitors that claer with the OBDII scanner or battery disconnnect and need to be "relearned" are :


Catalyst (CAT)
Exhaust Gas Recirculation (EGR)
Evaporative (EVAP)
Oxygen (O2) Sensor
Secondary Air
Heated Catalyst
Air Conditioning (AC) System
O2 Sensor Heater

The smog tech was telling me the " continous" monitors should always show ready regardless of drive cycles and mine were showing " not available or
" N/A". I went the Cheverolet dealer and they explained since the " continious" monitors are just that " continous" they are assumed to be present. As long as the " non continous" show " ready" or " not available" all should be good. You are allowed one " not ready " on the "non- continous" monitors. So, I drove through a couple of drive cycles and went to a drifernt smog shop and passed with no problem. I did have on monitor showing " not ready", this was the EVAP which can take along time to pull in as it monitors fuel level and pressures. But since I can get away with one not being ready I was good to go. Here are some good GM drive cycles to go through. It took mine two seperate drive cycles to learn .

http://www.bsecorp.com/files/techtips/ST9303l.pdf

and this one :
General Motors (specific) OBD II Drive Cycle

Performing a GM OBDII Driving cycle:

1. 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 in prior to the cold start or the heated oxygen sensor diagnostic may not run.
2. 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.
3. 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.
4. 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.
5. 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.
6. Accelerate. Accelerate at 3/4 throttle until 55-60mph (88-96 km/hr). This will perform the same diagnostics as in step 3.
7. 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.
8. Decelerate. This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears.

I strongly recommend doing this late at night to avoid getting other drivers angry if you go out on the freeway......