Good evening everyone, first time here. I'll try to keep this short and sweet.

About six months ago my lovely wife ran the transmission out of fluid in our '98 Blazer and of course the check engine light came on. I know, my fault I should have been making sure the fluids were good. lesson learned.

I want to preface this by saying the problem is now fixed with the tranny, but for months we were running the car with a code reader because in the mornings it was giving a P0785 code. Warming the car up and clearing the code worked for a day's worth of driving. The car had a lot of miles on it, and frankly we're too poor to take it to the shop.

Unfortunately the car would not pass smog in that condition, apparently daily clearing the code puts some of the emissions sensors into a diagnostic mode, automatically failing the car(according to the guy running the smog station).

Now this is where I stand, the problem was a galled plunger in the valve body. The tranny now works fine with no P0785 code coming up at all, however it looks to me like the sensors are still in the diagnostic mode as well as i can tell on the code reader.

Will the car snap out of it's diagnostic mode, and if so does anyone know how long that usually takes? Unfortunately the registration has passed, tho the fees are paid, and I can't drive it on the road to test it.

Any advice would be appreciated.

Jason

 

I may look new to the forum but have long been a lurker and have had my fair share of experience with evap issues. What has to happen is the vehicle runs a series of diagnostic sequences to check various emissions systems. If a fault is found or something is out of tolerance during these tests the CEL usually comes on. Sometimes it might take a couple of cycles for the CEL to come on if there is a problem. The only way complete those cycles is by driving the vehicle. Google "gm drive cycle" and that should give you an idea of what has to be done for the vehicle to pass the emissions tests.

 

I believe the computer stores something like the last 200 crank cycles try disconnecting the battery for a couple of days it might help

 

Disconnecting the battery wont clear the codes,you have to use a programer to clear them.