2010 Cadillac CTS Sedan AWD V6-3.6L Page 1405
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
A 3-way catalytic converter (TWC) 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 TWC. 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
TWC. 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
* Before the ECM can report DTC P0420 or P0430 failed, DTCs P0030, P0031, P0032, P0036, P0037, P0038, P0050, P0051, P0052, P0056,
P0057, P0058, P0100, P0101, P0102, P0103, P0121, P0122, P0123, P0131, P0132, P0133, P0135, P0137, P0138, P0140, P0141, P0151,
P0152, P0153, P0155, P0157, P0158, P0160, P0161, P0221, P0222, P0223, P0335, P0336, P0338, P2096, P2097, P2098, P2099, P2195,
P2196, P2197, P2198, P2232, P2235, P2237, P2240, P2243, P2247, P2251, P2254, P2270, P2271, P2272, P2273, P2297, P2298, P2626, and
P2629 must run and pass.
* DTC P000A, P000B, P000C, P000D, P0010, P0011, P0013, P0014, P0020, P0021, P0023, P0024, P0030, P0031, P0032, P0050, P0051,
P0052, P0100, P0101, P0102, P0103, P0116, P0117, P0118, P0119, P0121, P0122, P0123, P0128, P013A, P013C, P013E, P0130, P0131,
P0132, P0133, P0135, P0137, P0138, P014A, P0140, P0141, P0150, P0151, P0152, P0153, P0155, P0157, P0158, P0160, P0161, P0221,
P0222, P0223, P0300, P0301-P0306, P0443, P0455, P0458, P0459, P0496, P2088, P2089, P2090, P2091, P2092, P2093, P2094, P2095,
P2096, P2097, P2098, P2099, P2100, P2101, P2107, P2119, P2122, P2123, P2127, P2128, P2138, P2176, P2177, P2178, P2179, P2180,
P2187, P2188, P2189, P2190, P2232, P2235, P2270, P2271, P2272, or P2273 is not set.
* The engine speed is 1,080-3,000 RPM, or 1,160-2,440 RPM for LLT.
* The engine load is 13-45 percent, or 13-80 percent for LLT.
* The air flow into the engine is between 4-20 g/s and steady, or 3-28 g/s for LLT.
* The engine intake air temperature (IAT) is warmer than -30掳C (-22掳F).
* The HO2S 2 is at operating temperature for greater than a range of 140-300 seconds, or 140-210 seconds for LLT.
* The engine is operating in Closed Loop.
* The calculated TWC temperature is between 480-750掳C (896-1,382掳F) and steady, 500-900掳C (932-1,652掳F) for LLT.
* The difference between the expected TWC temperature and the calculated TWC temperature is less than 40掳C (72掳F).
* The difference between the expected exhaust gas mass flow and the calculated exhaust gas mass flow is less than 11 g/s.
* The above conditions exist for approximately 17 minutes.
* DTCs P0420 and P0430 run once a drive cycle. The ECM will attempt to run this diagnostic up to 3 times per drive cycle.
Conditions for Setting the DTC
The ECM determines the oxygen storage capacity (OSC) of the catalyst has degraded below a calibrated threshold for greater than 5 seconds.
Action Taken When the DTC Sets
DTCs P0420 and P0430 are Type A DTCs.
Conditions for Clearing the DTC
DTCs P0420 and P0430 are Type A DTCs.
Diagnostic Aids
Inspect for the following conditions, which may cause a catalytic converter to degrade:
* An engine misfire
* High engine oil or high coolant consumption
* Retarded spark timing
* A weak or poor spark
