Genpu 2008 SMOG help?

imallama

imallama

Greenie N00B Member
Long time lurker here with an 08 gen one MS3. Only mods it has on it are a CARB legal COBB intake (since I'm in California). Basically, I can't pass smog for whatever reason. I keep checking codes, and I'm getting a pending code of P0401 and occasionally one for the thermostat, but it hasn't actually thrown on the CEL.

The 2 monitors I need to get ready are the HCAT and O2, but everything else seems fine. After the initial failure, I've been driving it for well over 100+ miles, and yet neither monitor is ready. I've tried to look up drive cycles on how to get the HCAT and O2 monitor ready, but all I've read (and have tried) is driving the car at 55 mph for 15 min, then coasting down to 20 mph, then back up to speed.

Would appreciate any assistance! There are 107k miles on the car and I'm hoping to get it ready so I can sell it in the future (need a bigger car sadly).
 
have you cleared the HCAT and O2 codes? P0401 is for EGR
 
Raider said:
P0401 is a clogged EGR. Here is my how-to on cleaning it. https://mazdaspeeds.org/index.php?t...ed-3-6-or-cx-7-to-fix-the-p0401-cel-code.590/

If no other codes, that is probably why they are failing you.
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Thanks! I did read that and was planning on doing that just in case. It seems pretty straight forward, thanks for the guide!

Easter Bunny said:
have you cleared the HCAT and O2 codes? P0401 is for EGR
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So...that's the weird thing. There aren't any codes for HCAT or O2. I'm just not sure why the HCAT and O2 monitors are still marked as not ready, but everything else is. Have you had that issue before? I remember reading somewhere that mentioned if the O2 and HCAT aren't getting ready, it could be a battery thing but I don't see how that would affect anything.
 
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A weak Battery does all kinds of weird shit to these cars
 
Easter Bunny said:
A weak Battery does all kinds of weird shit to these cars
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Ah, rip. So if all else fails, may have to buy a new battery and see if it changes anything. Would you happen to know of any other drive cycle information for getting the O2 and HCAT ready? I've been reading through different Mazda forums and watching youtube vidoes, but it seems most of it is toward the EVAP monitor, which I'm not having an issue with.
 
Check the voltage when it's disconnected from the car
 
Easter Bunny said:
Check the voltage when it's disconnected from the car
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Will do this week! I also went ahead and ordered a replacement thermostat (to address the thermostate pending code which resolved when I checked it yesterday, along with the EGR pending code) just in case and will also do an EGR clean. Thanks for the help! Hope this fixes the monitors lol.
 
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