We recently received a query from an ADVRider reader asking whether a new California regulation applies to motorcycles.  The regulation in question requires vehicles to pass a biennial smog check.  While that part of the regulation is not new, it does add some new requirements that could be of significant interest to enthusiasts.  So we decided to check on the reader’s question.

Smog check

As amended, the new reg states that model year 1996 or newer vehicles with an ECU that’s not approved by the California Air Resources Board (CARB) will automatically fail the California biennial smog check.

As of July 19th, 2021, the California Bureau of Automotive Repair (BAR) is expanding the smog check test to accommodate the regulation.  The new procedure will check that each ECU is running factory software or a CARB-approved ECU tune.  If the vehicle is running software that does not meet these criteria, it will fail the smog check.  A failure means that the vehicle can not be registered or renewed until the ECU is brought into compliance.


The California Bureau of Automotive Repair is expanding smog checking requirements.

Testing for smog compliance

The test procedure involves plugging into the vehicle’s ECU and checking two pieces of data: the Calibration Identification (aka CAL ID) and the calibration verification number (CVN).  The CAL ID reveals the version of the software that is running.  The CVN is a calculated number based on how the vehicle runs using parameters checked by the ECU, with the numbers changing when the software is adjusted.  In addition, any aftermarket computer device like the ECU or an inline tuner must have an Executive Order (EO) number that is CARB approved.

In a Road & Track interview, SEMA Director of Emissions Compliance Peter Treydte said there’s not much to worry about for most owners.

“So far in the two weeks that have transpired, we have seen zero instances of concern.  “I really don’t think that this is problematic.”  –  Peter Treydte to Road & Track

Treydte says that only a tiny number of California vehicles are likely to violate the new rule.  And he backs this up with a data estimate received from BAR.  According to that data, approximately one million vehicles in California undergo smog testing each month, and only between 150 and 300 cars fail due to an illegal ECU tune.  By way of comparison, approximately 10,000 cars fail each month due to mechanical or non-ECU problems.


Californian motorcycles with modified ECUs may run afoul of a new California smog regulation.  Image credit: Motorhelmets

And, Treydte says that not all tuning ECUs are illegal.  There is a process for ECU manufacturers to submit their ECUs for evaluation.  If the ECU meets applicable smog limits, the manufacturer can obtain an Executive Order (EO) to have the component be considered CARB legal.

Are motorcycles affected?

So now that we know what California thinks and does about modified ECUs, we turn to the question of whether the new regulation pertains to motorcycles.  And with a little research, we’ve found that it does not.  Clicking on to CARB’s Frequently Asked Questions (FAQ) page, we see that motorcycles have been specifically exempted from the new California smog check regulation.

Actually, there’s a long list of vehicles that do not require a biennial smog check.  They are as follows:

  1. Gasoline-powered vehicles, hybrid vehicles, and alternative-fuel vehicles that are model-year 1975 and older.
  2. Gasoline-powered vehicles, hybrid vehicles, and alternative-fuel vehicles that are eight model years and newer do not require a biennial Smog Check.
  3. Gasoline-powered vehicles, hybrid vehicles, and alternative-fuel vehicles that are four model years and newer do not require a change-of-ownership Smog Check.
  4. Diesel-powered vehicles that are model-year 1997 and older.
  5. Diesel-powered vehicles with a gross vehicle weight rating of more than 14,000 pounds.
  6. Electric-powered vehicles.
  7. Motorcycles.

Why are motorcycles exempt from the smog check?

There’s no rationale given for why motorcycles have been exempted.  It’s interesting because some governments are targeting motorcycles in other parts of the world due to the sheer number of two-wheelers on the road.  With California having the strictest smog regulations in the USA, you must wonder why the state has decided to exempt them.

This is particularly interesting because, according to Statista, in 2019, California had the most motorcycle registrations of any other state in the nation.  There were a little over 808,000 registered bikes.  The state with the next highest number of registrations, Florida, has a registration count that has more than 200,000 fewer motorcycles.

So the takeaway from all this data is that motorcycles do not require a biennial smog check in California.  But with such a large number of motorcycles in the state, it would likely be worthwhile to keep an eye on revisions to the regulation.  Because if you are running a modified or piggyback ECU, it will be important to know whether it is CARB certified.

If we become aware of any changes to this reg that pertains to motorcycles, we’ll let you know.

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