DTC P0420 - LLU
Diagnostic Instructions
DTC Descriptor
DTC P0420 00: Catalyst System Low Efficiency
Circuit/System Description
Note: A new converter with less
than 160 km (100 miles) on it may set
DTC P0420 00 due to out-gassing of the internal matting.
Operating the vehicle at motorway speeds for approximately 1 h
may correct the condition.
A 3-way catalytic converter (TWC) controls emissions by
converting hydrocarbons (HC) and carbon monoxide (CO) into carbon
dioxide (CO2), and oxides of nitrogen (NOX) into nitrogen. The 3
way catalytic converter also stores oxygen. When the listed driving
conditions are met, the catalyst system efficiency test will run.
The engine control module (ECM) monitors this oxygen storage
capacity by comparing the pre and post-catalyst oxygen sensor
signals while adding and subtracting fuel during specific driving
conditions. The ECM compares the pre and post-catalyst oxygen
sensor signals to determine if the oxygen storage capacity of the
catalyst is degraded.
Conditions for Running the DTC
• |
DTCs P0030 00, P0031 00,
P0032 00, P0036 00, P0037 00, P0038 00,
P0100 00, P0101 00, P0102 00, P0103 00,
P0121 00, P0122 00, P0123 00, P0130 00,
P0131 00, P0132 00, P0133 00, P0134 00,
P0135 00, P0136 00, P0137 00, P0138 00,
P0140 00, P0141 00, P0171 00, P0172 00,
P0221 00, P0222 00, P0223 00, P0300 00,
P0301 00, P0302 00, P0303 00, P0304 00,
P0313 00, P0420 00, P0444 00, P0458 00,
P0459 00, P1138 00, P2096 00, P2097 00,
P2197 00, P2188 00, P2270 00, and P2271 00 are
not set. |
• |
The engine speed is between
1 400-3 200 RPM. |
• |
The evaporative emission (EVAP) purge
concentration is learned. |
• |
The engine load is between 15-50%. |
• |
The vehicle is in closed loop. |
• |
The calculated exhaust mass gas flow is between
5-55.56 g/sec, and stable. |
• |
The engine coolant temperature (ECT) at engine
start is colder than -10.5°C (+50.9°F) |
• |
The ambient temperature is more than -15°C
(+5°F). |
• |
The heated oxygen sensor 2 has exceeded the
dew point for more than 60 s. |
• |
This diagnostic attempts one test during each
period when the above conditions have been met. This diagnostic
attempts up to 4 tests during each drive cycle. |
Conditions for Setting the DTC
• |
The ECM has determined the catalyst efficiency has
degraded below a calibrated threshold. |
• |
This diagnostic may conclude in 6 test
attempts which will require at least 2 drive cycles. However,
this diagnostic may require as many as 8 test attempts.
Depending on driving conditions, more than 2 drive cycles may
be required. Each test attempt may conclude within approximately
1 min. |
Action Taken When the DTC Sets
DTC P0420 00 is a Type A DTC.
Conditions for Clearing the DTC
DTC P0420 00 is a Type A DTC.
Diagnostic Aids
Inspect for the following conditions, which may cause a
catalytic converter to degrade:
• |
High engine oil or high coolant consumption |
• |
A damaged oxygen sensor or wiring harness |
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Testing
Caution: Refer to
Three-Way Catalytic Converter Damage
Caution in the Preface section.
Caution: Refer to
Heated Oxygen Sensor Resistance Learn Reset
Caution in the Preface section.
- Engine idling, observe the DTC information with a scan
tool. Verify there are no Heated Oxygen Sensor or misfire DTCs
set.
- Verify the following conditions do not exist with the
catalytic converter:
• |
A severe discolouration caused by excessive
temperatures |
• |
An internal rattle caused by damaged catalyst
subset |
⇒ |
If a condition is found, replace the catalytic
converter |
- Verify the following conditions do not exist with the
exhaust system:
• |
Loose or missing hardware |
• |
Properly torqued B52A Heated Oxygen
Sensor 1 or B52B Heated Oxygen Sensor 2 |
⇒ |
If a condition is found, repair the exhaust
system. |
⇒ |
If the DTC fails this key cycle, continue with
this procedure. |
- Verify the following conditions do not exist with the
B52B Heated Oxygen Sensor 2:
• |
A grounded B52B Heated Oxygen Sensor 2,
wiring harness |
⇒ |
If a condition is found, replace the
B52B Heated Oxygen Sensor 2. |
- If no physical condition is detected and the
B52B Heated Oxygen Sensor 2, is as active as the
B52A Heated Oxygen Sensor 1, after operating the engine
at 1 500 RPM for 1 min and then returning to a
stabilised idle, then replace the catalytic converter.
Repair Instructions
Note: A new converter with less
than 160 km (100 miles) on it may set
DTC P0420 00 due to out-gassing of the internal matting.
Operating the vehicle at motorway speeds for approximately 1 h
may correct the condition.
Perform the
Diagnostic Repair Verification after completing the diagnostic
procedure.
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