I purchased my 2014 Vanquish back in September.

After driving it about 150 miles, I got the dreaded “Emissions Service Required” along with a P0136 Code Oxygen Sensor circuit fault (bank 1 sensor 2).
I cleared the code and drove it another 50 miles, and the code re-appeared. I cleared it again and it re-appeared after about 30 miles.
I remember from my first DB9 that if the car is driven differently than the last several drives, the Emissions Service warning can appear and will reset once the ECU catches up with the driving pattern. (I experienced this after a sporty mountain drive several years ago).

I decided to not reset the code this time and just drove the car as it seemed to be running well. While I was out and making a few stops, I remembered that we have 100 octane available here in Las Vegas. I assumed that the Vanquish V12 has similar octane requirements as the DB9, so I added 3.5 gallons to bump the octane an bit and proceeded to my next stop. While it might be my imagination, that car seemed to run smoother after adding the gas. When I made my next stop (about 7 miles), once I restarted the car, the fault was gone.

Not sure if it was coincidence or if the octane boost had something to do with the reset.
I looked in the owners manual and on-line, and cannot find the actual octane requirements of the Vanquish. I’m thinking it’s mapped the same as the DB9 at 97, but want to be sure and would like confirmation if anyone knows this.

Also, has anyone noticed any correlation between the lower octane fuels in the US, and the ECU throwing the Emission Service fault as some of the O2 sensor operating parameters may be close to thresholds with the lower octane gas?

Long post - thanks if you read this far……

Best,

Jim

 

Could very well be.

However US doesn't have generally lower octane fuel.

The European/World measurement uses one method to measure octane: RON , which is a straight chemical measure (Research) that generally reads high, whereas North America uses the average of RON & MON (aka R+M/2, or anti knock index AKI), where MON is evaluated through a Mechanical test and reads low.

A DB9 fuel requirement of 97 RON will be ~92 AKI on US pumps.

Its also possible that your ECU was resetting its knock fuel table trims for short term and long term after you cleared the fault, so it indeed learns and adapts for local fuel and driving style, and does so much faster when reset.