My 1999 GMC Sierra C1500 with A/T just failed the North Carolina annual Safety/Emissions test. The reasons indicated are MIL Commanded-On, P078/Shift Solenoid B Electrical and P1870/Description Not Available. The shop manager said the P1870 has something to do with some type of clutch.

According to the Vehicle Inspection Receipt/ Statement, everything else has passed. The shop manager said that anytime the "Service Engine Soon" light is on they automatically fail the vehicle and the required check list accompanying the inspection results indicates "X" (failure) of all items. But the Inspection receipt indicates everything passed with the exception on MIL Commanded-On. Removing the Pos battery cable for a while resets the "Service Engine Soon" light but the light comes back on after driving about one mile.

While I understand that the A/T will eventually need to be rebuilt, it does not seem to prevent safe operation of the vehicle and I have been keeping a check on the engine codes in the event other problems should rear their ugly heads.

Should this vehicle have actually "Failed"? I'd like to here from an unbiased Pro, e.g. someone not looking to sell me a new transmission and is the a way to make the "Service Engine Soon" light stay off long enough to get the NC inspection done?

I sincerely appreciate any advice. :-)

I just found some possible help for you, here is a link. Copy an paste link in your browser, hope this helps!

I smogged my 1996 GMC SLE 1500 & the code P1870 came up. What do i need to do to fix it? - Yahoo! Answers (http://answers.yahoo.com/question/index?qid=20071129193948AANuKgV)

My 1999 GMC Sierra C1500 with A/T just failed the North Carolina annual Safety/Emissions test. The reasons indicated are MIL Commanded-On, P078/Shift Solenoid B Electrical and P1870/Description Not Available. The shop manager said the P1870 has something to do with some type of clutch.

According to the Vehicle Inspection Receipt/ Statement, everything else has passed. The shop manager said that anytime the "Service Engine Soon" light is on they automatically fail the vehicle and the required check list accompanying the inspection results indicates "X" (failure) of all items. But the Inspection receipt indicates everything passed with the exception on MIL Commanded-On. Removing the Pos battery cable for a while resets the "Service Engine Soon" light but the light comes back on after driving about one mile.

While I understand that the A/T will eventually need to be rebuilt, it does not seem to prevent safe operation of the vehicle and I have been keeping a check on the engine codes in the event other problems should rear their ugly heads.

Should this vehicle have actually "Failed"? I'd like to here from an unbiased Pro, e.g. someone not looking to sell me a new transmission and is the a way to make the "Service Engine Soon" light stay off long enough to get the NC inspection done?

I sincerely appreciate any advice. :-)

First, the diagnostic trouble codes need to be fault traced to determine what is actually setting them. If it comes down to needing solenoids replaced, that can be done short of a transmission overhaul or rebuild but a thorough diagnosis is critical.
As far as the check engine light being on, that light isn't motivated by 'safety' but rather it's motivated by tail pipe emissions. When something is detected by the computer algorithms as something interfering with emissions, the light will come on.