5.
Read "DTC Status" parameter.
The catalyst’s efficiency is demonstrated by its ability to oxidize CO and hydrocarbon emissions. The Powertrain Control Module (PCM) compares the output signals of the front and rear oxygen sensors to determine whether the output of the rear sensor is beginning to match the output of the front oxygen sensor. Air/fuel mixture compensation keeps the frequency of the front oxygen sensor high due to the changes from rich-to-lean combusition. The catalyst causes the rear oxygen sensor to have a lower frequency. As the catalyst wears, the rear oxygen sensor’s signal trace begins to match the front oxygen sensor’s signal trace. That is because the catalyst becomes saturated with oxygen and cannot use the oxygen to convert hydrocarbon and CO into H₂O and CO₂ with the same efficiency as when it was new. A completely worn catalyst shows a 100% match between the frequency of the front and rear sensors.
If amplitude of B1S2 is different from the model value during 60 sec under enable conditions, PCM sets DTC P0420.
Item | Detecting Condition | Possible Cause |
DTC Strategy | ● Oxygen storage capacity (Deterioration ofCatalytic efficieny) | ● Exhaust system ● B1S2 ● Catalyst converter |
Enable Conditions | ● Engine speed 800∼3000rpm ● Engine load 28.8 ∼65.3 % ● Catalyst temp.(model) 500∼800℃ ● Closed loop control ● There is not misfire. ● There is not malfunction on HO2S / PCSV / ECTS. | |
Threshold Value | ● amplitude of downstream O2 sensor ＞ 0.3 | |
Diagnostic Time | ● 60 sec | |
MIL ON Condition | ● 2 driving cycle |
※ B1S1 : upstream oxygen sensor / B1S2 : downstream oxygen sensor
Connect scantool to Data Link Connector(DLC).
IG "ON".
Select "Diagnostic Trouble Codes(DTCs)" mode, and then Press F4(DTAL) to check DTC'sinformation from the DTCs menu
Confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditionsnoted in the freeze frame data or enable conditions noted in the DTC detecting condition.
Read "DTC Status" parameter.
Is parameter displayed "History(Not Present) fault"?
History fault : DTC occurred but has been cleared.
Present fault : DTC is occurring at present time.
▶ Fault is intermittent caused by poor contact in the sensor’s and/or ECM’s connector or wasrepaired and ECM memory was not cleared. Thoroughly check connectors for looseness,poor connection, bending, corrosion, contamination, deterioration, or damage.Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.
▶ Go to "Terminal ＆ Connector Inspection" procedure
Exhaust gas system check.
Visual check.
Check air leakage at junction of HO2S or Catalyst converter.
Check looseness, poor connection, or damage.
Is there something wrong?
▶ Repair as necessary and then, go to "Verification of Vehicle Repair" procedure.
▶ Go to "Component inspection" procedure.
Rear HO2S(B1S2) check.
B1S2 visual check
Check assembling state of B1S2. (Check the interference between sensor wiring and exhaust pipe.)
Check corrosion, contamination, or damage on sensor terminal and connector.
Is there something wrong?
▶ Repair as necessary and then, go to "Verification of Vehicle Repair" procedure.
▶ Go to "Catalyst converter check" procedure.
Catalyst converter check.
Catalyst converter visual check.
Check discoloration by over-heating.
Check deflection or crack(hole).
Check noise.
Check whether the catalyst converter is genuine.
After erase the DTC, drive the vehicle more than 60sec sccording to "Enable Conditions" (Refer to "DTC Detecting Condition"). And then, confirm DTC.
Is there something wrong?
▶ Substitute with a known-good Catalyst Converter and check for proper operation. If the problem iscorrected, replace Catalyst Converter and then go to "Verification of Vehicle Repair" procedure.
▶ Many malfunctions in the electrical system are caused by poor harness(es) and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage. So, check poor connections and the related circuit between ECM and component thoroughly. Repair as necessary and go to "Verification of Vehicle Repair" procedure.
After a repair, it is essential to verify that the fault has been corrected.
Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode.
Press F4(DTAL) and confirm that "DTC Readiness Flag" indicates "Complete".
If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions.
Read "DTC Status" parameter.
Is parameter displayed "History(Not Present) fault"?
▶ System performing to specification at this time. Clear the DTC.
▶ Go to the applicable troubleshooting procedure.
