E39 / P0420 00
Read the instructions below then
start the fault diagnostic procedure.
Symptom: Malfunction Indicator Lamp
Three Way Catalytic Converter. Malfunction.
Fault symptom
Malfunction Indicator Lamp
On-board diagnosis
Type of diagnosis:
Enable criteria:
| Coolant temperature more than 40°C. |
| Engine running more than 5 minutes. |
| Calculated catalytic converter temperature below 800°C. |
| Closed loop lambda control active. |
| The above conditions must be fulfilled for 17 minutes. |
| ____________________________________ |
| Closed loop delayed in rich mode until O2S2 shows rich. |
| Closed loop delayed in lean mode and time is measured until O2S2 shows lean. |
Fault criteria:
| Too short time to O2S2 shows lean, indicating that the catalytic converter's oxygen storing ability is poor. |
Diagnostic help
Diagnosis regards:
| Faulty catalytic converter. |
Functions in the diagnostic tool related to the fault:
| (See also description of readings/activations in diagnostic tool) |
