DTC P0420

DTC: P0420 Catalyst system efficiency below threshold

Activation requirement CHECK ENGINE lamp:
After two consecutively "performed" tests with fault.

Activation of CHECK ENGINE lamp:
None.

Test to detect fault:
Oxygen sensor 2 (G3/1) (after catalytic converter) is required for this test. To begin the test, the following conditions must be met simultaneously:
^ Oxygen sensor control approved
^ Load approximately 25-45 %
^ Vehicle speed approximately 47-50 mph (75-80 kmh)
^ Vehicle speed constant
^ Engine coolant temperature above approximately 76 °C for at least 10 minutes
^ Oxygen sensor signals at least 16 oscillation shifts and frequency greater than 1.5 Hz
^ Minimum signal range of oxygen sensor 2 (after catalytic converter) exceeded (approximately 200 mV)
^ "catalytic converter hot" message from engine control module via CAN

The diagnostic module compares the oscillations of both oxygen sensor signals for phase shift (time delay). The oscillation from "rich" to "lean" or vice versa has a time delay between the oxygen sensor 2 (after catalytic converter) and the oxygen sensor 1 (before catalytic converter). If a specified value is exceeded (approximately 160° Phase shift), the catalytic converter has reached its aging limit.