Catalyst Monitor

OBD System Description - Catalyst Monitor

Catalyst Bank1

DTC Description / Detecting Condition / Confirmation Procedure
P0420 refer to DTC P0420: Catalyst System Low Efficiency. P0420

Monitor Strategy Description
The ICMD Diagnostic manipulates Air/Fuel ratio and stores the times it takes for the pre and post converter oxygen sensors to switch. It then calculates EWMA values and compares them against calibratable thresholds in order to determine the PASS/FAIL status.

Malfunction Criteria
EWMA Oxygen Storage Time for Bank 1 >= 2.25 s (passing) 2.75

Enable Conditions
Engine Runtime >= 570 sec.
AND Purge Concentration Learned = TRUE
AND Airflow <= 8.5 g/s (For AT), 7.5 g/s (For MT)
AND Airflow >= 2.25 g/s
AND Throttle position <= 1.5015%
AND Coolant Temperature >= 70 degrees C
AND Coolant Temperature <= 109 degrees C
AND Ambient Temperature >= -7 degrees C
AND Ambient Temperature <= 105 degrees C
AND Barometer >= 72 kPa
AND Too many test attempts <= 12
AND Closed Loop enabled = TRUE
AND Torque Fuel Reduction active = FALSE
AND Catalyst Temperature <= 975 degrees C
AND Catalyst Temperature >= 300 degree C
AND Fuel Integrator deviation from stoichiometric <= 0.03
AND Vehicle speed <= 3 kph
AND AT not in P/N (for PN Mode Selected = FALSE, AT only) = TRUE
AND BLM Learn completed = TRUE
AND Low idle airflow not present (airflow delay complete) = TRUE
AND Air/Fuel ratio ramping = FALSE
AND Idle Time <= 75 sec.
AND Test not complete = FALSE
AND Disabling Faults Present = FALSE
AND Instrumentation slews active = FALSE
AND OFVC device control active = FALSE

Time required
Time Length and Frequency:
Test runs a maximum of 2 tests per key cycle unless step change detected (6 tests per key cycle after step change detected).




MODE $06 Data