Catalyst Efficiency Monitor

CATALYST EFFICIENCY MONITOR

The powertrain control module (PCM) monitors the oxidation catalytic converter (DC) during the diesel particulate filter regeneration. The PCM determines if the temperature increase across the catalyst is correct to support a thorough and efficient reduction of soot to ash. The PCM uses the DC inlet temperature, measured by exhaust gas temperature bank 1, sensor 1 (EGT11) and the DC outlet temperature, measured by EGT bank 1, sensor 2 (EGT12) to calculate the temperature increase.

The catalyst efficiency monitor is enabled and runs continuously during a regeneration after a short time delay, to allow the DC to light-off. The catalyst efficiency monitor runs only when certain base engine conditions are first satisfied. The typical monitoring duration for this monitor is 2 minutes. Inputs from the crankshaft position (CKP), engine coolant temperature (ECT), EGT11, EGT12, and diesel particulate filter pressure sensors are required to enable the monitor. The monitor entry conditions include:
- diesel particulate filter regeneration is active
- ECT is greater than -40°C (-40°F)
- no fuel injector concerns

The PCM continuously monitors the temperature increase. The PCM compares the measured increase against a minimum expected value. The minimum expected value is based on the amount of fuel injected for regeneration. A fault filtering counter starts when the monitor begins to run. When the temperature increase is less than 25% of the minimum expected increase, the counter increases. When the temperature increase is greater than 25% of the minimum expected increase, the counter decreases. If the number of counts on the counter at the end of the monitor exceeds a calibrated limit the diagnostic trouble code (DTC) P0420 is set and the malfunction indicator lamp (MIL) illuminates.