Smog Readiness, Specifically Catalyst

I am Jacks N54

Sep 10, 2018
Ventura, CA
e90 335i
This is mildly embarrassing, but I'm posting this in hopes that it will save someone else the time, frustration, and gas I wasted.

I recently moved down to CA and need to smog the car. It had catted downpipes and an old GIAC flash, amongst other things. I swapped back in the OEM downpipes and started doing the readiness procedures and driving a lot. Everything became ready except for catalyst so I kept driving and doing drive cycles, driving and doing drive cycles... rinse and repeat.

Long story short, after driving a metric shit-ton, I started thinking about the flash and called GIAC to get info. Dead end, so I decided to try using MHD to flash the car back to Stage 0, but keep MHD installed so I can monitor. I flashed and skipped the options, because I ASSumed it would be "stock". That was my mistake. In the MHD User Guide, it clearly states:

OEM Catted Downpipe(s)

This flash option should be selected if you still have the OEM downpipe(s) installed. It removesthe logic to suppress the CEL so that the OBD readiness tests can run successfully

Since this was my first flash with MHD, I hadn't set any options previously and the default for this option is unchecked. I set my options making sure this one was on, and two days later I'm smog ready.

Lessons learned:

1. Read the fucking manual
2. Review the fucking options (even if you think Burbles are just for children)


  • Federal Drive Cycle Test Procedure.pdf
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