VAG-COM
View Readiness
(VAG 1551/1552 function 15)

The Readiness Code is a set of 8 bits, each of which 
corresponds to one monitored  emissions "system" 
in an OBD-II car. When all readiness bits show "pass", 
it means that all systems have been checked and pass
 the on-board tests. 

Whenever you clear DTC's or remove power from the ECU, 
all readiness bits will be set to "fail". Most cars do not have 
all 8 systems, so as soon as you apply power again, 
the bits corresponding to systems that are not 
actually in the car will come up "pass" again. 

The above screen-shot was taken immediately after
clearing the DTC's in a 1997 VR6.   You can see that
this car does not support "monitors" for the EGR, 
Catalyst Heating, or Air Conditioning.   The car does
not have EGR or Catalyst Heating.  It does have Air
Conditioning, but a "monitor" is only required if the 
system uses ozone-depleting refrigerant (R12).

It takes a variety of specific driving conditions to "test" all 
the systems. It can be done in a short time using a very
 specific and complicated procedure found in the 
On Board Diagnostic section of the Repair Manual 
for your engine. We've never had the patience
 to  work  through this procedure successfully. 
. The alternative is just to drive the car for 2-3 days.
 Make sure you include at least one short highway trip, 
and your Readiness Bits should all read "Pass" again.

Note:

This function is only available on
Engine Controllers that are OBD-II compliant
(all 1996 and newer US-Model gasoline engines).

Non-US models and TDI's may not support this
function even though they are otherwise OBD-II 
compliant.  OBD-I did not require any "monitors". 

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