Buick Regal: DTC P0420

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0420

Catalyst System Low Efficiency

Circuit/System Description

The catalyst within the converter promotes a chemical reaction, which oxidizes the hydrocarbons and the CO that are present in the exhaust gas. This process converts the hydrocarbons and the CO into water vapor and carbon dioxide (CO2), and reduces the NOx, converting the NOx into nitrogen. The catalyst also stores oxygen. The engine control module (ECM) monitors this process by using heated oxygen sensors (HO2S) that are in the exhaust stream before and after the 3- way catalyst. The HO2S produces an output signal that the ECM uses to calculate the oxygen storage capacity of the catalyst.

This indicates the ability of the catalyst to convert the exhaust emissions efficiently. The ECM monitors the efficiency of the catalyst by monitoring the HO2S during an off-idle, decel fuel cut off (DFCO) event. When the catalyst is functioning properly, the post catalyst HO2S response to the fuel conditions during the DFCO event is slow compared to the response of the pre catalyst HO2S. When the post HO2S response is near that of the pre HO2S, the oxygen storage capability and efficiency of the catalyst may be degraded below an acceptable threshold.

Conditions for Running the DTC

• DTC P0030, P0031, P0032, P0036, P0037, P0038, P0053, P0054, P0068, P0101, P0102, P0103, P0106, P0107, P0108, P0111, P0117, P0118, P0119, P0121, P0122, P0123, P0128, P0131, P0132, P0133, P0135, P0137, P0138, P013A, P013B, P013E, P013F, P0141, P015A, P015B, P0171, P0172, P0201, P0202, P0203, P0204, P0222, P0223, P0261, P0262, P0264, P0265, P0267, P0268, P0270, P0271, P0300, P0301, P0302, P0303, P0304, P1248, P1249, P124A, P124B, P16F3, P2101, P2135, P2147, P2148, P2150, P2151, P2153, P2154, P2156, P2157, P2270, or P2271 is not set.
• The engine speed is between 950 - 2, 950 RPM to enable the catalyst diagnostic. Once the engine speed is in range, the engine speed must be between 900 - 3, 050 RPM to keep the test enabled.
• Accelerator pedal position is at most 4 %.
• Ethanol estimation is not active.
• Evaporative emission (EVAP) purge is not active.
• Post HO2S heater is ON for greater than 180 s.
• Mass air flow (MAF) is between 2 - 13 g/s.
• System voltage is between 10 - 32 V.
• Vehicle speed is between 64 - 126 km/h (40 - 78 MPH) to enable the catalyst diagnostic.
• To keep the test enabled the vehicle speed is between 56 - 132 km/h (35 - 82 MPH).
• Catalyst calculated temperature is between 500 - 900ºC (932 - 1, 652ºF).
• Engine is operating in closed loop.
• Engine is operating in DFCO.

This diagnostic attempts one test during each valid OFF-idle period once the above conditions have been met. This diagnostic attempts up to 4 tests during each drive cycle.

Conditions for Setting the DTC

The ECM determines that the efficiency of the catalyst has degraded below a calibrated threshold.

Action Taken When the DTC Sets

DTC P0420 is a Type A DTC.

Conditions for Clearing the DTC

DTC P0420 is a Type A DTC.

Diagnostic Aids

Inspect for the following conditions, which may cause a catalytic converter to degrade:

• Engine misfire
• High engine oil or high coolant consumption
• Retarded spark timing
• Weak or poor spark
• Lean fuel mixture
• Rich fuel mixture
• Damaged oxygen sensor or wiring harness

Reference Information

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

1. Ignition On.

2. Verify there are no other DTCs set.

• If other DTCs are set

Refer to Diagnostic Trouble Code (DTC) List - Vehicle.

• Go to next step: If no other DTCs are set

3. Operate the vehicle within the Conditions for Running the DTC.

4. Verify the scan tool Catalyst Monitor Not At Idle Test Conditions Met parameter changes to Yes.

• If Yes is not displayed

Refer to step 3.

• Go to next step: If Yes is displayed

5. Verify the Catalyst Monitor Test Result parameter displays Passed when performing the steps listed below:

1. Monitor the scan tool Catalyst Monitor Test State parameter. When the parameter indicates Active, the Catalyst Monitor Test is running.

NOTE: When the test has completed, the Catalyst Monitor Test Counter will increment by one and the Catalyst Monitor Test Result will indicate Passed, Failed or No Result.

2. Continue to monitor the parameter. When the parameter indicates Inactive, the Catalyst Monitor Test has completed.
3. Verify the scan tool Catalyst Monitor Test Result displays Passed.

• If No Result is displayed

Repeat steps 3 - 5 until the Test Result parameter indicates Passed or Failed

• If Failed is displayed

Refer to Circuit /System Testing

• Go to next step: If Passed is displayed

6. All OK.

Circuit/System Testing

1. Verify the conditions listed below do not exist with the catalytic converter:

• Dents
• Severe discoloration caused by excessive temperatures
• Road damage
• Internal rattles caused by damaged catalyst substrate
• Restrictions
  • If a condition is found

    Replace the catalytic converter.

  • Go to next step: If no condition is found

2. Verify the conditions listed below do not exist with the exhaust system:

• Leaks
• Restrictions
• Physical damage
• Loose or missing hardware
  • If a condition is found

    Repair or replace the component as necessary.

  • Go to next step: If no condition is found

3. Verify the conditions listed below do not exist with the B52B Heated Oxygen Sensor 2:

• Incorrect torque
• Damage
  • If a condition is found

    Replace the B52B Heated Oxygen Sensor 2 or repair the condition as necessary.

  • Go to next step: If no condition is found

4. Replace the catalytic converter.

Repair Instructions

• Warm Up Three-Way Catalytic Converter Replacement (2.0L LTG)
• Exhaust Leakage
• Heated Oxygen Sensor Replacement - Sensor 2
• Perform the HO2S Heater Learn procedure with a scan tool after replacing a heated oxygen sensor.
• Restricted Exhaust

Repair Verification

1. Install any components that have been removed or replaced during diagnosis.

2. Perform any adjustments, programming or setup procedures that are required when a component is removed or replaced.

3. Clear the DTCs with a scan tool.

4. Turn Off the ignition for 60 s.

5. Operate the vehicle within the Conditions for Running the DTC.

6. Verify the scan tool Catalyst Monitor Not At Idle Test Conditions Met parameter changes to Yes.

• If Yes is not displayed

  Refer to step 5.

• Go to next step: If Yes is displayed

7. Verify the Catalyst Monitor Test Result displays Passed when performing the steps listed below:

1. Monitor the scan tool Catalyst Monitor Test State parameter. When the parameter indicates Active, the Catalyst Monitor Test is running.

NOTE: When the test has completed, the Catalyst Monitor Test Counter will increment by one and the Catalyst Monitor Test Result will indicate Passed, Failed or No Result.

2. Continue to monitor the parameter. When the parameter indicates Inactive, the Catalyst Monitor Test has completed.
3. Verify the scan tool Catalyst Monitor Test Result displays Passed.
   • If No Result is displayed

     Repeat steps 5 - 7 until the Test Result indicates Passed or Failed

   • If Failed is displayed

     Refer to Circuit /System Testing

   • Go to next step: If Passed is displayed

8. All OK.

DTC P0442

Diagnostic Instructions

• Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
• Review Strategy Based Diagnosis for an overview of the diagnostic approach.
• Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0442

Evaporative Emission (EVAP) System Small Leak Detected

Circuit/System Description

The engine off natural vacuum (EONV) test is the small leak detection diagnostic for the evaporative emission (EVAP) system. This diagnostic tests the EVAP system for a small leak when the key is turned OFF and the correct conditions are met. Heat from the exhaust system is transferred into the fuel tank while the vehicle is operating. When the vehicle is turned OFF and the EVAP system is sealed a change in the fuel tank vapor temperature occurs which results in a corresponding pressure change in the fuel tank vapor space. This change is monitored by the engine control module (ECM) using the fuel tank pressure (FTP) sensor input. With a leak in the system, the amount of pressure change will be less than that of a sealed system.

Conditions for Running the DTC

• DTCs P010B, P012B, P012C, P012D, P0101, P0102, P0103, P0106, P0107, P0108, P0111, P0112, P0113, P0114, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0128, P012B, P012C, P012D, P0222, P0223, P0236, P0237, P0238, P0443, P0446, P0449, P0452, P0453, P0455, P0458, P0459, P0461, P0462, P0463, P0496, P0498, P0499, P0502, P0503, P0722, P0723, P111E, P117D, P017C, P017D, P017B, P117B, P117F, P117E, P117C, P2066, P2067, P2068, P1221, P222B, P222C, P222D, P222E, P262B. are not set.
• The barometric pressure (BARO) is greater than 70 kPa.
• The engine coolant sensor (ECT) is greater than 63ºC (145ºF)
• The fuel level is between 10 - 90%.
• The start-up engine coolant temperature (ECT) and the start-up intake air temperature (IAT) are within 8ºC (14ºF).
• The engine run time before shut-off was greater than 10 min.
• The drive distance before engine shut-off was greater than 5 km (3 mi).
• The ambient air temperature at the end of the drive cycle is between 0 - 34ºC (32 - 93ºF).
• DTC P0442 runs once per drive cycle during the hot soak period after the ignition is turned OFF and may require up to 40 min to complete. The control module will not make more than 2 test attempts per day. The time since the last completed engine off natural vacuum test must be at least 17 h if passed or 10 h if failed.

Conditions for Setting the DTC

• The ECM detects a leak in the EVAP system that is greater than a calibrated amount.
• The ECM must complete several engine off natural vacuum tests before the diagnostic can turn the MIL ON or OFF.

Action Taken When the DTC Sets

DTC P0442 is a Type A DTC.

Conditions for Clearing the DTC

DTC P0442 is a Type A DTC.

Diagnostic Aids

• The EVAP system can be filled with smoke more quickly and completely by opening the system opposite the end where the smoke is injected. When injecting smoke at the service port tool temporarily leave the EVAP Vent Solenoid Valve open until smoke is observed then close the system and continue testing.
• To help locate intermittent leaks using the GE 41413-A , move all EVAP components while observing smoke with the GE 41413-SPT.
• Individual components can be isolated and tested using adapters in the GE 41413-300.
• When servicing the EVAP system, test pressure must not exceed 13 in H20 (0.5 PSI) as pressure in excess of this could cause system components to perform inaccurately.
• A condition may exist where a leak in the EVAP system only exists under a vacuum condition.
• This type of leak may be detected by using the scan tool Purge/Seal function to create a vacuum in the EVAP system and then observe the FTP Sensor parameter for vacuum decay.

Reference Information

Schematic Reference

Engine Controls Wiring Schematics (LTG)

Connector End View Reference

Component Connector End View Index

Powertrain Component View

Powertrain Component Views

Description and Operation

Evaporative Emission Control System Description

Electrical Information Reference

• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

Special Tools

• CH 48096 EVAP Service Port Access Tool
• GE 41413 - A Evaporative Emissions System Tester (EEST)
• GE 41413 - 300 EVAP Cap and Plug Kit
• GE 41413 - SPT High Intensity White Light

For equivalent regional tools, refer to Special Tools (Diagnostic Tools) and Special Tools (Mechanical Tools).

Circuit/System Testing

NOTE:

• Refer to the GE 41413-A detailed instructions in Evaporative Emission System Diagnosis.
• Larger volume fuel tanks and/or those with lower fuel levels may require several minutes for the floating indicator to stabilize or produce smoke from a leak.
• Ensure that the underbody temperature of the vehicle and the tester are similar.

1. Disconnect the purge tube at the quick connector on the EVAP canister side of the Q12 Evaporative Emission Canister Purge Solenoid Valve and install the CH 48096.

2. Connect the GE 41413-A to the CH 48096.

3. Command the EVAP Purge/Seal function to Not Venting or System Seal with a scan tool to seal the EVAP system.

4. Use the flow meter on the GE 41413-A calibrated to 0.51 mm (0.020 in) to determine if there is a leak.

• If a leak is detected

1. Use the GE 41413-A to apply smoke to the EVAP system at the purge tube service port until the leak is located using the GE 41413-SPT.
   • If leak is detected, repair or replace the affected component as necessary.

• Go to next step: If no leak is detected

5. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

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