AD07.61-P-4000-07B | Aging of oxygen sensor upstream of TWC ME-SFI fault code description | with code (620a) vehicles with catalytic converter system |
1 | Fault code | on right upstream of TWC on left upstream of TWC |
2 | Fault storage Actuation of the engine diagnosis (EURO3/4) or CHECK ENGINE malfunction indicator lamp (MIL) | following expiry of the checking time and fault following two successive driving cycles with faults |
3 | Checking frequency | continuously |
4 | Checked signal or status | A Correction variable exceeded B Cycle duration too long |
5 | A Correction variable limit values B Cycle duration limit value Checking duration | approx. 1.2 s (ATV) < approx. 7.5 s (mean value from 9 measurements) < 80 s |
6 | Check prerequisites | - Engine speed approx. 1000-2000 rpm - Load approx. 15 - 50 % - Catalytic converter temperature > 300 °C - Lambda control enabled - No fault in catalytic converter effect - No fault in oxygen sensor heater |
7 | Check procedure | The oxygen sensors downstream of the TWC are necessary for checking catalytic converter effectiveness and for improving lambda control (dual-sensor control). The oxygen sensor signals are used to form the mean lambda value, from which a correction variable for lambda control is determined. With the correction variable (value in the case of a new oxygen sensor approx. 0), aging of the oxygen sensor upstream of the TWC is compensated within certain limits. If the correction variable exceeds the limit value, the oxygen sensor upstream of the TWC must be replaced. In addition, the cycle duration of the sensor signal is evaluated. |
8 | | Cycle duration of the oxygen sensor upstream of the TWC too long: oxygen sensor downstream of the TWC is not monitored further. Correction variable of the oxygen sensor upstream of the TWC exceeded: oxygen sensor downstream of the TWC continues to be monitored. If faults are simultaneously detected for the oxygen sensor upstream and downstream of the TWC, only the oxygen sensor downstream of the TWC is generally defective. |