DTC P0420 or P0430
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC P0420
- Catalyst System Low Efficiency Bank 1
DTC P0430
- Catalyst System Low Efficiency Bank 2
Circuit/System Description
Note: A new converter with less than 100 mi on it may set DTC P0420 or P0430 due to out-gassing of the internal matting. Operating the vehicle
at highway speeds for approximately 1 h may correct the condition.
A 3-way catalytic converter controls emissions of hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx). The catalyst within
the converter promotes a chemical reaction, which oxidizes the HC and the CO that are present in the exhaust gas. This process converts the HC
and the CO into water vapor and carbon dioxide (CO2), and reduces the NOx, converting the NOx into nitrogen. The catalytic converter also stores
oxygen. The engine control module (ECM) monitors this process by using a heated oxygen sensor (HO2S) that is in the exhaust stream after the
3-way catalytic converter. The HO2S 2 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 allowing the
catalyst to heat, then wait for a stabilization period while the engine is idling. The ECM then adds and removes fuel while monitoring the HO2S 2.
When the catalyst is functioning properly, the HO2S 2 response to the extra fuel is slow compared to the response of the HO2S 1, which is located
before the 3-way catalytic converter. When the HO2S 2 response is near that of the HO2S 1, the oxygen storage capability and efficiency of the
catalyst may be degraded below an acceptable threshold.
Conditions for Running the DTC
* DTCs P0030, P0031, P0036, P0037, P0038, P0068, P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0121, P0122, P0123,
P0125, P0128, P0130, P0131, P0132, P0133, P0134, P0135, P0136, P0137, P0138, P0140, P0141, P0171, P0172, P0201, P0202, P0203,
P0204, P0205, P0206, P0207, P0208, P0220, P0300, P0315, P0326, P0327, P0336, P0340, P0341, P0442, P0446, P0452, P0453, P0455,
P0496, P0500, P0502, P0506, P0507, P0601, P0602, P0606, P0641, P0722, P0723, P1133, P1134, P1516, P1621, P2135, P2138, P2176 are
not set.
* Before the ECM performs the idle test, the vehicle must be driven under the following conditions:
- The engine speed is greater than 1,300 RPM.
- The engine run time is greater than 100 s.
- Both conditions exist for greater than 16 s.
* The vehicle speed is less than 1.6 km/h (1 mph).
* The throttle position is less than 2 %.
* The mass air flow (MAF) is between 2-21 g/s.
* The engine is operating in Closed Loop.
* The fuel trim learn is enabled.
* The engine coolant temperature (ECT) is between 45-129锟斤拷C (113-264锟斤拷F).
* The barometric pressure (BARO) is greater than 70 kPa.
* The Catalytic Converter Calculated Temperature parameter is between 600-900锟斤拷C (1,112-1,652锟斤拷F) for greater than 6 min.
* The intake air temperature (IAT) is between -20 and +250锟斤拷C (-4 and +482锟斤拷F).
* The battery voltage is greater than 11 V.
* The transmission is in Drive Range-Automatic transmissions only.
* The short term fuel trim is between -10 and +10 %.
* The engine is idling for less than 50 s.
* This diagnostic attempts one test during each valid idle period when the above conditions have been met. This diagnostic attempts up to 8
tests during each drive cycle.
Conditions for Setting the DTC
The ECM has determined the catalyst efficiency has degraded below a calibrated threshold.
Action Taken When the DTC Sets
