Wherein you spend a Saturday morning in third gear on the interstate
If you have a Honda or Acura that has an “incomplete” result on its emissions test because of the EGR monitor, this is how you fix it.
My 2020 Acura MDX recently got a REJECT result on its state-mandated emissions test. The data from the EGR (Exhaust Gas Recirculation) monitor was “Incomplete.” Normally this indicates a recent battery swap or code clear, meaning the monitors haven’t built up enough data. But modern Hondas are notorious for needing a complicated drive cycle to clear the EGR monitor.
The Ritual
Standard advice is a 20-minute highway cruise with some coasting. On newer Honda and Acura V6 engines, that doesn’t seem to be enough. After some trial and error and pestering an Acura dealership service manager, I found the sequence that works.
Here is the ritual to perform:
- Warm Up: Drive until the engine hits at least 170°F. On my dash, this is about one-third to one-half of the way up the temp gauge.
- Highway Cruise: Accelerate to 60 mph and hold it for 30 seconds.
- Coast: No throttle and no brake for 5 seconds.
- Italian Tune-up: Downshift (using the paddles or sport mode) to over 5,000 RPM for a portion of the drive. The EGR system needs high-load, high-RPM transitions to trigger its self-test.
- Repeat: Do this cycle two or three times.
It feels silly to be screaming down the highway in third gear in a three-row SUV, but the ECU wants a little abuse before it vouches for your tailpipe.
Own Your Data
If you can manage it, don’t go to the inspection station blind. I use the OBDLink MX+ to read vehicle status. It’s a Bluetooth dongle that plugs into the standard port under the dash and talks to a phone app. It has presets for various states and will tell you if you’re good to go in whichever one you pick.
And I just like having an OBD monitor, because data is fun.
Lucas Bergman is a software engineer who enjoys occasionally explaining to local law enforcement that he’s just “cycling the monitors.”