2010 Cadillac CTS Sedan AWD V6-3.6L Page 1402
瀚慖f greater than the specified range, test the low reference circuit for an open/high resistance or for a short to voltage. If the
circuit/connections test normal, replace the K20 ECM.
4. Install the fuse that supplies B+ to terminal 56-X2 of the K20 ECM.
5. Ignition ON, test for greater than 4.8 V between the 5 V reference circuit terminal 3 and ground.
瀚慖f less than the specified value, test the 5 V reference circuit for an open/high resistance. If the circuits/connections test normal, replace
the K20 ECM.
6. Test for 4.8-5.2 V between the signal circuit terminal 2 and ground.
瀚慖f greater than specified range, test for a short to voltage in the signal circuit. If circuit/connections test normal, replace the K20 ECM.
瀚慖f less than the specified range, test for a short to ground or an open/high resistance in the signal circuit. If circuit/connections test normal,
replace the K20 ECM.
7. If all circuits/connections test normal, replace the B23 camshaft position sensor.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* Camshaft Position Sensor Replacement - Bank 2 (Left Side) Exhaust (See: Powertrain Management/Computers and Control
Systems/Camshaft Position Sensor/Service and Repair/Camshaft Position Sensor Replacement - Bank 2 (Left Side) Exhaust)
* Camshaft Position Sensor Replacement - Bank 2 (Left Side) Intake (See: Powertrain Management/Computers and Control
Systems/Camshaft Position Sensor/Service and Repair/Camshaft Position Sensor Replacement - Bank 2 (Left Side) Intake)
* Camshaft Position Sensor Replacement - Bank 1 (Right Side) Exhaust (See: Powertrain Management/Computers and Control
Systems/Camshaft Position Sensor/Service and Repair/Camshaft Position Sensor Replacement - Bank 1 (Right Side) Exhaust)
* Camshaft Position Sensor Replacement - Bank 1 (Right Side) Intake (See: Powertrain Management/Computers and Control
Systems/Camshaft Position Sensor/Service and Repair/Camshaft Position Sensor Replacement - Bank 1 (Right Side) Intake)
* Control Module References (See: Testing and Inspection/Programming and Relearning) for ECM replacement, setup, and programming
P0420
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
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,
