P0420
DTC P0420 CATALYST SYSTEM EFFICIENCY BELOW THRESHOLD (BANK 1)Component Location:
COMPONENT LOCATION
GENERAL DESCRIPTION
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 conversation. 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.
DTC DESCRIPTION
If the catalyst Efficiency is higher threshold value, the PCM determines that a fault exists and a DTC is stored.
DTC Detecting Condition:
MONITOR SCANTOOL DATA
1. Ignition "OFF"
2. Connect Scantool and Engine "ON"
3. Monitor the HO2S parameters and signal waveform on scantool.
4. Are those HO2S1 and HO2S2 within specifications?
YES: Fault is intermittent caused by poor contact in the sensor's and/or PCM's connector or was repaired and PCM memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.
NO: Go to "System Inspection" procedure.
SYSTEM INSPECTION
1. Check Exhaust system
1. Visually/physically inspect the following conditions:
- Exhaust system between HO2S and Three way catalyst for air leakage.
- Damage, and for loose or missing hardware:
2. Has a problem been found in any of the above areas?
YES: Repair as necessary and go to "Verification of Vehicle Repair" procedure.
NO: Go to "Component Inspection" procedure.
COMPONENT INSPECTION
1. Check Rear HO2S
1. Visually/physically inspect the rear HO2S for the following conditions:
- Ensure that the HO2S is securely installed.(Pigtail and wiring harness not making contact with the exhaust pipe)
- Check for corrosion on terminals.
- Check for terminal tension (at the HO2S and at the PCM)
- Any damage.
2. Has a problem found in any of the above areas?
YES: Repair as necessary and go to "Verification of Vehicle Repair" procedure.
NO: Go to "Check TWC" as below.
2. Check TWC
1. Visually/physically inspect the three-way catalyst(TWC) converter for the following damage:
- Severe discoloration caused by excessive temperature.
- Dents and holes.
- Internal rattle caused by a damaged catalyst.
2. Also, ensure that the TWC is a proper original equipment manufacturer part.
3. Has a problem been found?
YES:
- Substitute with a known - good TWC and check for proper operation.
- If the problem is corrected, replace TWC and go to "Verification of Vehicle Repair" procedure.
NO:
- Substitute with a known - good PCM and check for proper operation.
- If the problem is corrected, replace PCM and go to "Verification of Vehicle Repair" procedure.
VERIFICATION OF VEHICLE REPAIR
After a repair it is essential to verify that the fault has been corrected.
1. Monitor and record the Freeze Frame Data for the Diagnostic Trouble Code(DTC) which has been diagnosed.
2. Using a Scantool, Clear the DTCs.
3. Operate the vehicle within conditions noted in the freeze frame data or enable conditions.
4. Monitor that all readiness tests have been verified as "Complete"
5. Are any DTCs present?
YES: Go to the applicable troubleshooting procedure.
NO: System is performing to specification at this time.