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.
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.
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:
- 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.
- Continue to monitor the parameter. When the parameter indicates
Inactive, the Catalyst
Monitor Test has completed.
- 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
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
2. Verify the conditions listed below do not exist with the exhaust system:
- Leaks
- Restrictions
- Physical damage
- Loose or missing hardware
3. Verify the conditions listed below do not exist with the B52B Heated
Oxygen Sensor 2:
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:
- 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.
- Continue to monitor the parameter. When the parameter indicates
Inactive, the Catalyst
Monitor Test has completed.
- Verify the scan tool Catalyst Monitor Test Result displays Passed.
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.
- 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.
READ NEXT:
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.
Diag
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.
Diag
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.
Diag
SEE MORE:
FRONT SUSPENSION DESCRIPTION AND OPERATION
The front suspension has 2 primary purposes:
Isolate the driver from irregularities in the road surface.
Define the ride and handling characteristics of the vehicle.
The front suspension absorbs the impact of the tires travelling over
irregular road su
Diagnostic Instructions
Perform the Diagnostic System Check prior to using this diagnostic
procedure: Refer to Diagnostic System
Check - Vehicle
Review the description of Strategy Based Diagnosis: Refer to Strategy
Based Diagnosis
An overview of each diagnostic category can be found here: R