On Sun, 20 Sep 2015 15:49:16 -0700, sms
wrote:

On 9/20/2015 9:12 AM, Scott Dorsey wrote:
sms wrote:
On 9/19/2015 10:51 PM, Ewald Böhm wrote:
On Sat, 19 Sep 2015 05:30:45 -0400, Steve W. wrote:

How do you figure that "almost no states use OBD" testing. In fact most
of the states do not use a dyno any longer.

I just had mine tested, in California, and they used a dyno.
No OBD hookup whatsoever.

How did they check for pending codes if they did not use a code scanner?
You can't pass with more than two pending codes (one on some years).

They look for the light on the dashboard that indicates codes have been
logged.

In some places they always use the scanner to make sure, for instance,
that the ECU wasn't reset immdiately before taking the car in for
inspection. In some places they do not.

Well in California they definitely check via the OBD-II port. I had
replaced a battery and there were no dashboard lights indicating
anything. The first thing they did was to do a scan for codes.

The number of pending codes that is allowable varies by year of
manufacture. A good shop will tell you the drive sequence to clear the
pending codes for each model. A bad shop won't even know this information.
Actually it is not pending codes that are the issue. It is the
readiness monitors.. Can't remember how many readiness monitors there
are - but there's a catalyst monitor, a O2 sensor monitor, and EGR
monitors, and O2sensor heater and cat heater monitor on some vehicles.
These are the intermittent monitors that need to be "set" .

Setting the monitor just means they have been through one or more
test sequences and have aquired valid data..

The rest of the monitors are contimuous monitors - misfire,
component, and fuel system, nonitors.

The evap monitor, for instance, is only "valid" in a fixed temperature
range, and with the tank between something like 1/4 and 3/4 full (not
100% sure of the actual numbrs). If you reset the codes or replace
the battery on a vehicle with the tank full or almost empty you can
NOT set the readiness monitor for the evap system - so virtually ALL
OBD2 based emission test facilities will allow at least one monitor to
be un-set or not ready.

If you know what code is coming up, and want to "cheat" the system, if
you can avoid setting that particular monitor, while setting all the
others, you can sometimes get a vehicle to pass. You need to
understand the drive cycle and what can cause the monitor you want
dissabled to fail to set. (and it needs to be an intermittent or
non-continuous monitor. The usual culprits are Cat, evap, or EGR.