Hey guys. I went to get my smog inspection today, and the car passed the emissions test, but failed the OBD self diagnostic test. The guy asked me if I had recently disconnected the battery...which I had last night to fix a low idle and CEL I had. After I reconnected, the car has ran fine and no CEL. So after it failed the first time he told me to drive around for about 30-40 miles to get the computer to reset itself. Did that.....drove for exactly 39 miles and re-tested. Still failed for the same reason. I have no idea what causing the problem. Car is running fine and there is no CEL on the dash .

The actual test sheet say:
Fail: System Malfuntion Light

If I werer to jumper the ECU, would it show the supposed problem, even if the dash light isn't lit?
I don't want to take it to the dealer to pay 50 bucks for them to tell me nothing is wrong.....but I don't want to put some more miles on the car and try to re-test it again for another $15 and it have the same problem.
Any input guys?
I'd appreciate it.

Thanks,
Chris

 

Just ran a OBD2 scanand I get no codes. Anybody know anything about "drive cycling" in order to get the ECU to re-learn?

 

What the smog station is referring to is the "readiness test". These test are run by the computer under certain conditions to check system integrity and functionality.
They include the O2, catalytic, evaporative etc. The computer will tell the OBD2 scanner whether the test for that system is complete, not complete or not available.

If everything were working correctly and with the ecu reset, a drive cycle should pass all test within about 5-10 miles. A complete drive cycle would include the following conditions: cold start up where the coolant and intake temperatures are within about 10F degrees of each other, a mixture ofstop and go driving, steady freeway cruising for at least 30 seconds, freeway decelerating. If after 15 miles of driving and the test has not complete, usually something is wrong.

You can bypass a "2 trip code" by grounding the DLC or jumping the CEL jumper plug. So if you were to reset the ecu and do a cold start up and go through a complete drive cycle, the ecu will set a code if something is not right with a system.

Find out which system is not completing and go from there. I know of a few cases where people blew their backup/radio fuse which would "reset" the computer everytime they shut off the vehicle. This would also reset the readiness test, which would cause the vehicle to fail the inspection part of a smog test.

Good luck.




Modified by elmo at 6:35 PM 10/16/2004

 

Thanks man.....the driving I did after I reset the ECU was only 30 miles of less than 40 mph, and no freeway driving.

I'm gonna drive all this week to and from work, (freeway, stop and go traffic as well as surface street driving) and have it checked again on saturday. That should put at least 150 miles on it through all sorts of driving conditions.

The car is still running fine, and as I said before, I did a OBD scan and it passed with no codes.

 

anybody else?

 

my bro's 96 accord had an unplugged 02 sensor. i plugged it back in, and it took 100+ miles to clear the readiness code. he had gone back at 50 miles, and the smog guy read the OBD port saying that it was still not ready. it didnt have a CEL the entire time

you should be able to go back for free after another 50miles and pass

 

Thanks man.....thats kind of what I'm thinking. From what I've read, it's all a matter of getting in the right combination of driving cyles. I'll give it a week or so and have them re-test.