What Does It Mean?
This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to OBD-II equipped vehicles (Dodge, Ram, Ford, GMC, Chevrolet, VW, Audi, Toyota, etc.). Although generic, the specific repair steps may vary depending on the make/model.
If your OBD-II equipped vehicle has stored a P0433 code, it means the Powertrain Control Module (PCM) has detected a problem with the catalytic converter efficiency for engine bank two. Bank 2 indicates the malfunction occurred in the engine bank that does not contain cylinder #1.
The catalytic converter is used to reduce exhaust emissions produced by diesel and gasoline engines. Its key component is a filter block, composed of ceramic fibers interwoven with platinum and other precious metals, enclosed in an inline steel housing and positioned in the exhaust system. Nitrogen oxide (N2O) particles, carbon monoxide, and unburned hydrocarbons are reduced into harmless ions of nitrogen, oxygen, carbon dioxide, and water inside the catalytic converter.
Emission reduction is achieved using the dense filter block combined with the extreme heat from the engine exhaust. Temperatures inside the catalytic converter must reach at least 800 degrees Fahrenheit to effectively reduce emission levels. Signals from the upstream and downstream oxygen (O2) sensors are used by the PCM to monitor catalytic converter efficiency.
Exhaust gases are pushed through the manifold, into the exhaust pipe, past the upstream O2 sensor, and through the catalytic converter. After passing through the catalytic converter, they pass the downstream O2 sensor.
If the signals from the upstream and downstream O2 sensors reflect an exhaust oxygen concentration that is too similar, a P0433 code will be stored and a Malfunction Indicator Lamp (MIL) may illuminate.
Other Bank 2 catalyst efficiency trouble codes include P0430, P0431, P0432, P0434, P0435, P0436, P0437, P0438, and P0439.
Code Severity and Symptoms
A stored P0433 code could indicate the fuel delivery system isn’t operating correctly. It should be treated as severe.
Symptoms of this code may include:
Decreased fuel efficiency
A lack of overall engine performance
Other associated diagnostic trouble codes
MIL (Malfunction Indicator Lamp) illumination
Causes
Possible causes for this code being set include:
Faulty catalytic converter
Misfire(s)
A faulty mass airflow or manifold absolute pressure sensor
Faulty O2 sensor(s)
Burned, broken, or disconnected wiring and/or connectors
Engine exhaust leak upstream of the catalytic converter
Diagnostic and Repair Procedures
A diagnostic scan tool, a digital volt ohmmeter (DVOM), and a reliable source of vehicle information (such as All Data DIY) will be needed to diagnose a P0433 code.
Any misfire codes, throttle position sensor codes, manifold absolute pressure codes, or mass airflow sensor codes should be addressed before attempting to diagnose a stored P0433 code. The engine must also be running efficiently before diagnosing a P0433.
I would typically start with a visual inspection of the system wiring harnesses and connectors. I would focus on harnesses routed near hot exhaust pipes and manifolds, as well as those routed near sharp objects like exhaust shields.
I would continue by connecting the scan tool to the vehicle’s diagnostic port and retrieving all stored trouble codes and freeze frame data. I like to write this information down as it can prove helpful if this turns out to be an intermittent code. Intermittent codes can be much more difficult to diagnose.
Next, I would clear the codes and test drive the vehicle.
If the P0433 reset immediately, I would start the engine and allow it to reach its normal operating temperature. I would let it idle (with the transmission in neutral or park) and use the scanner’s data stream to observe the O2 sensor input data. Limiting the data stream to include only relevant data will provide a more accurate data sample.
If the engine is running efficiently, the upstream O2 sensor will cycle regularly from one millivolt (0.100 volts) to nine millivolts (0.900 volts) and the downstream O2 sensor data should reach a midpoint and settle there, after the PCM enters closed-loop operation. If the signals from the upstream and downstream O2 sensors are too similar, after the PCM has reached closed-loop operation, suspect a faulty catalytic converter.
Consult your vehicle information source for the recommended vehicle specifications and use the DVOM to check the resistance of the O2 sensor in question. Disconnect all associated controller electrical connectors before attempting to test the system circuit resistance with the DVOM.
Additional Diagnostic Notes:
The presence of a stored P0433 does not automatically condemn the catalytic converter
O2 sensor failure is more common than catalytic converter failure
Reconditioned catalytic converters are far less reliable than new OEM replacements