Hi, I have an OBDII scan tool and I cleared the codes after making repairs on the car. It need cap, rotor, wires and plugs. After about 3 weeks all the same codes appeared again, car is running fine. I cleared them again, stayed clear for about 3 weeks and came back a second time. I read in the manual that there is some type of run test that must be performed to completly clear the codes, but the scan tool says to refer to the car manual and the car manual makes no mention of any such test. Does anyone know how to get these codes cleared once and for all.
Merry Christmas
Lou

Lou,

The run test refers to the vehicles readiness state. A complete drive cycle will usually reset the monitors to ready status, and once they are back to that status, they will be ready to read any codes.

If you are seeing your codes come back, the problem is not corrected.

Out of curiosity, what are you seeing re-appear?

I received all engine misfire codes, PO300, then several indicating which cylinder. The car was running rough this summer before I replace all the ignition items. Now it remains code free for about 3 weeks. I need to get the car through NJ inspection. It passed all the actual inspections but the codes showed up when they used the OBDII port. Since I am able to clear the codes for a few weeks I am hoping it will go through the next time I take it.

Won't solve your immediate problem but consider a long term solution. Get rid of Frank Lautenberg and all the other worthless liberal democrats that own and operate Joisee. WHen the dems go, usually the EPA and its inept bureaucrats follows. Just a thought ; ) We've kept um out of most of VA.

I am not a NJ resident, but I could not agree more. Lucily Mainers have thus far escaped the long arm of the EPA, having defeated the infamous "Car Test" facilities a number of years back. It is truly ridiculous when the emissions are fine, but the block heads still mandate that a MIL will = failure of the test. The assumption that every P code will be emissions related is just false.

BB (Maine resident, Rebublican, Volvo Owner)

What are you running for plugs? If single prong, check that the gap is correct at .28

Is the entire ignition system stock?

Is th car a turbo or N/A?

If not, and it contains higher output components, try increasing the plug gap, assuming you have the single prong plugs.

When you clear the codes take it out for a spin and come back and check again, even if the MIL is no on, to see if there are any pending codes. Or, have you already done that? If there are pending codes, the inspectors would fail it even if the MIL is not on.

BB

The car is non turbo.

They are single prong and everything is stock. It has been driven several thousand miles since I added the stuff and I have checked it multiple times and it reads 0 codes, then all of a sudden all the same codes come up again, I clear them and it will read 0 for 2-3 weeks before they show up again. Thanks for the help, I will check the gap again, aggrevating that it passed the emissions part of test and failed only for the stored codes.