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Converter no ready, O2 sensor not ready - Mazda 6

I just failed inspection because check engine light is on. The codes state that catalytic converter and O2 sensor are “not ready”. Tried to research on line, but could not find anything very helpful. I understand it has to do with the computer but not much else. Someone on Mazda 6 message board provided a complicated sequence of driving instructions including maintaining various speeds and RPMs for specific lengths of time which they said would reset the computer. My mechanic is at a loss. I was wondering if anyone had any thoughts on the issue and suggestions for resolving it. If I take it to the dealer, do you have any idea how much it will cost to fix. This car is a lemon and I would just like to get the inspection done so I can trade it in and get something that doesn’t keep breaking. Let me know if you would like a 2004 5 speed Mazda 6 with 70k. Thanks.

On some vehicles the readiness monitors can be reset by simply driving over time without a problem. On other vehicles, it requires a specific drive cycle to reset the readiness monitors. If the readiness monitors don’t reset from simple driving over time, then you operate the vehicle exactly under the conditions recommended to reset the readiness monitors.

I know it’s a hassle and takes time, but that’s the only way to reset the readiness monitors.


No thanks on your offer. I already have a 2004, 5 speed Mazda 6 lemon. I bought it used about 4.5 years ago and while I’m still paying for the car, I’ve also put over $4,000 in repairs into the vehicle during that time. I estimate there are an additional $2,500 in repairs that should be made, but I am ignoring out of shear frustration and a lack of available cash. Sorry I don’t have an answer to your computer problem. Just wanted to let you know you’re not alone in your Mazda 6 lemon misery. Good luck.

If you’re lucky it’s just a blown fuse. See this link, it’s a Ford but yours should work the same.

Guys, the ‘Check Engine’ light (CEL) is on because a Diagnostic Trouble Code (DTC) should be set. The readiness monitors do NOT turn on the CEL. If no DTCs come up when the system is scanned, that could indicate a failure of the module. Your current mechanic may not have the correct equipment to figure out the true cause.

However, 87_Ranger’s idea to check the fuses is a good and cheap check. The fuse may be listed on the fuse diagram as ‘PCM Memory’ or simply ‘ECM’.

I expect someone – maybe you? – tried to turn the CEL off by disconnecting the battery. The folks who make the car – and the EPA – have already thought of this. The engine computer knows the battery was disconnected, and it tattle tells on you at the emissions shop. The emissions shop is not allowed to test the car until the computer has had a chance to determine whether or not the car’s engine is performing up to snuff emissions-wise. And it can’t tell if the battery has been disconnected, until it has been driven a number of times and in various ways, then it knows one way or another. The computer is simply saying you have to drive the car a few days, then if everything is ok, it will turn off those “not ready” indicators. But if everything isn’t ok, the CEL will come back on.

You’ll need to fix whatever is causing the problem to pass emissions. FAce the problem straight on. You can’t get around it. Post the DTC’s (diagnostic trouble codes) here, then the folks who are experts here will analyze them and tell you how to fix it so it will pass emissions.

Thats a good point from BustedKnuckles. When i had this problem on my 97 Explorer the CEL was not on & no CEL at the thread i linked to. Maybe D2denizen will come back with more details.