Background:
Starting in 1996 all cars (in USA) have to conform to US-EPA rules called OBD-2. For convenience Hondas follow this in many other countries as well.

Part of the OBD-2 rules says the emmission-control system must perform certain tests on itself, to verify it's working OK. These are called "readyness" codes and they must be set OK before your car will pass an OBD-2 smog check.

If the readyness codes are not set, that does NOT cause the check-engine light. I just means the system hasn't finished testing itself. One big reason for this is to prevent a car from going through the test immediately after the ECU has been reset.

I'll start out this thread; from the Helm shop manual for 2003-2006 Accord 4-cyl. Anyone with a Helm book for other years can post up what they learn.

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How to Set OBD-2 Readyness Codes for 2003-2006 Accord 4-cylinder:

Catalytic Converter:
ECT coolant temperature above 158ºF (70ºC)
IAT air temperature above -13ºF (-25ºC)
VSS road speed above 3mph (4.8km/hr)
Drive some stop & go, and some constant cruising, about 5 miles.

EVAP system:
Battery voltage above 10.5v
Engine to be left Idling.
ECT coolant temperature between 176ºF to 212ºF (80-100ºC)
MAP pressure less than 6.75psia (46.6kPa)
= (manifold vacuum at least 7.95psi or 55kPa)
VSS speed = zero
IAT temperature between 32ºF to 212ºF (0-100ºC)

A/F sensor (primary O2 sensor):
ECT coolant temperature above 158ºF (70ºC)
Drive including some steady cruising 50-62mph (80-100km/hr) for 10 seconds.
Drive including closed-throttle engine-braking for 5 seconds.

A/F sensor Heater:
Start & Idle for at least 1 minute

Misfire detection:
Always available
Always monitoring
This one pauses & resets when driving on rough road

Fuel system monitor:
Always available
Always monitoring (during closed-loop operation)
Pauses when Cat, EVAP, & A/F monitors activate

Comprehensive:
Always available
Always monitoring

EGR monitor:
ECT coolant temperature above 176ºF (80ºC)
Drive steady (4th or D) above 50mph (80km/hr) for 10 seconds.
Engine braking (closed throttle) from above 62mph (100km/hr) for 5 seconds.
Make sure OBD-2 error code P0401 is NOT showing.

 

Emission codes require a 2 trip "engine cycle" to set a CEL.
But will show a "Not Ready" on the first trip.

 

The engine light turned off yesterday during my second trip of the day. Thank you all for all the help.