P20EEF0 (Engine nitrogen and oxygen emissions exceed the limit value of 1.2g/kWh failure).
OBD light is on, which activates the driver guidance system, and after the rated time, the vehicle will be torque-limited and speed-limited.
The vehicle is running in normal condition. For instance, the exhaust temperature is greater than the limit value, the exhaust flow is in the reasonable range, SCR conversion efficiency based on Nox signal will be compared with the threshold value in a period of time; the error will be reported, and the anti-cheating function in the induction system will be enabled if the value is less than the threshold value for two consecutive times; eventually the vehicle will be torqued and speed limited after the rated time.
IDSS and urea concentration gauge.
1. Check the urea concentration; use the portable urea concentration gauge to confirm the error, the standard data is 32.5%; if not qualified, replace the urea solution;
2. Remove the nozzle and conduct the spray test to observe if the nozzle atomization is normal; replace the nozzle if it still blocks after cleaning;
3. Check the mixer ( from the nozzle installation hole) to see whether there are a lot of crystals or not; clear it if so;
4. Check SCR carrier efficiency; use IDSS when the vehicle is running in a high-speed operating condition (about 80km/h, SCR upstream exhaust temperature at about 280°C), then compare the upstream nitrogen and oxygen value with the downstream nitrogen and oxygen value; observe the conversion efficiency, if the efficiency is low as in Figure 1, the SCR carrier may have HC poisoning or S poisoning;
5. Oil sampling; take out 500ml fuel from the malfunctioning vehicle by using a clean receptacle to check out the fuel quality closely;
6. Use IDSS particle evaluation to trigger the regeneration; wait for the end of the regeneration to monitor the upstream nitrogen and oxygen value and downstream nitrogen and oxygen value again (about 80km/h and SCR upstream exhaust temperature are around 280°C for about 30 minutes); observe the conversion efficiency during the test (if the discrepancy between those two values is large), the efficiency will be restored as shown in Figure 2; if still no efficiency, replace the SCR carrier.
