2004Slickside said:
Yep, finding a place to do it is most often the problem. With a Tech 2 scanner you can force each test to run. Sorry, that's the problem with clearing codes. It clears the readiness monitors as well. Keep in mind that pending problems not yet setting a code can cause the readiness monitor tests to not run as well. You may not have whatever problem you previously experienced fixed yet.
What is most troublesome to me is that the O2 Sensor Heater readiness test does not run immediately. IMHO this test should run right away. Seems something is keeping some tests from running. Here are some conditions that can keep such readiness tests from running (admittedly for Blazer not Avalanche). I just happened to have easy access to them. Note that IAT matching ECT at startup within a certain amount is in 2 of the 3 examples. You might want to start looking there. Also see if the rest of the mentioned parameters seem reasonable. Just use your Blue Driver to access the correct PIDs.
Note that these conditions must be met for a specific test to even run. Has nothing to do with passing or failing the test (that's another set of conditions).
As an example (2004 Blazer)
CONDITIONS FOR RUNNING THE DTC P0440 - Evap
* No active MAP sensor DTCs
* No active TP sensor DTCs
* No active VS sensor DTCs
* No active O2 sensor DTCs
* No active ECT sensor DTCs
* No active IAT sensor DTCs
* DTC P0125 not active
* The system voltage is between 10-17 volts
* The fuel level is between 12.5-87 percent .
* The ECT is between 4?C-30?C (39?F-86?F)
* The IAT is between 4?C-30?C (39?F-86?F)
* The cold start temperature difference (ECT minus IAT) is less than 1.5?C when the IAT is more than the ECT or 8?C when the ECT is more than the IAT
* The BARO is more than 73 kPa
CONDITIONS FOR RUNNING THE DTC P0420 Catalyst
* No active secondary AIR DTCs
* No active CMP sensor DTCs
* No active ECT sensor DTCs
* No active EGR DTCs
* No active Fuel Trim DTCs
* No active IAC DTCs
* No active IAT sensor DTCs
* No active MAF sensor DTCs
* No active MAP sensor DTCs
* No active O2 sensor DTCs
* No active transmission DTCs
* No active EVAP system DTCs
* No active TP sensor DTCs
* No active VS sensor DTCs
* No active misfire DTCs
* The engine speed is 900 RPM or more for more than 35 seconds since the last idle period.
* The engine has been running for more than 346 seconds and the long term fuel trim is stable.
* The predicted catalyst temperature is more than 475?C (887?F) .
* The system is in Closed Loop.
* The BARO is 73 kPa or more.
* The IAT is between -7 to 117?C (20-167?F) .
* The ECT is between 75-117?C (167-243?F) .
* The engine has been idling for less than 60 seconds .
* The actual engine speed is within 100 RPM of the desired idle speed.
CONDITIONS FOR RUNNING THE DTC P0135 O2 Sensor heater
IMPORTANT: This test is void if the system voltage remains outside the specified range for more than 4 seconds .
* The system voltage is between 11.7-17 volts .
* The MAF is less than 27 g/s .
* The engine run time is more than 2 seconds .
* The ECT sensor is less than 33?C (91?F) .
* The IAT is less than 33?C (91?F) .
* The difference between the ECT and IAT is no more than 5?C (9?F) .