What does it mean?
This is a generic diagnostic trouble code (DTC) that applies to OBD-II equipped vehicles with a catalytic converter temperature sensor. This may include, but is not limited to, vehicles from Dodge, Ford, Chevrolet, Dodge, Ram, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.
When an OBD-II equipped vehicle has stored a P046B code, it means that the Powertrain Control Module (PCM) has detected a discrepancy between the temperature signals from the catalytic converter of engine bank two. (Bank 2) refers to the engine bank that does not contain cylinder number one. To the best of my knowledge, only diesel applications use catalytic temperature sensors.
Clean diesel combustion vehicles require various types of diesel exhaust fluid injections to remove harmful emissions from the catalytic converter. Diesel Exhaust Fluid (DEF) is injected into the catalytic converter to raise the catalyst temperature and burn off trapped nitrogen oxide particles inside. These vehicles use catalytic temperature sensors (as opposed to oxygen sensors) to monitor the efficiency of the catalytic converter. Using temperature to monitor catalyst efficiency is the most accurate and practical method.
Sensor 1 and Sensor 2 may also be referred to as the upstream and downstream catalytic temperature sensors, respectively. The sensors are typically placed just before and immediately after the catalyst in the exhaust system. When the engine is running and sufficiently warmed up, the exhaust gases entering the catalytic converter should be significantly cooler than the exhaust gases exiting the converter. This holds true regardless of the DEF system’s status. The PCM constantly monitors the catalytic temperature sensors and compares the two sensor signals. If the degree of variation between the two is not within a programmed value, a P046B code will be stored, and a Malfunction Indicator Lamp (MIL) may also illuminate.
How severe is this DTC?
Catalyst temperature variation is crucial for reducing exhaust emissions from diesel engines. Although this code may be accompanied by no driving symptoms, from an environmental perspective, it should be classified as severe.
What are some of the symptoms of the code?
Symptoms of a P046B trouble code may include:
There may be no symptoms with this code
Heavy black exhaust smoke (more than usual)
Other DEF and catalytic converter codes
Reduced fuel efficiency
Increased exhaust emissions
What are some common causes of the code?
Causes
of this P046B transmission code may include:
Faulty exhaust temperature sensor
Bad catalytic converter
DEF system malfunction
Burned or otherwise open/short-circuited wiring in the exhaust temperature sensor system
What are the P046B troubleshooting steps?
If I were diagnosing a P046B code, I would want a diagnostic scanner, a digital volt/ohmmeter (DVOM), an infrared thermometer (with a laser pointer if possible), and a reliable vehicle information source (such as AllData DIY).
Please ensure the DEF system is filled with the correct fluid and is operating correctly. If there are any DEF-related codes, I would diagnose and repair them before attempting to diagnose a P046B. I would inspect all wiring and connectors related to the system. Focus on harnesses routed near hot exhaust pipes and manifolds.
Connect the scanner to the vehicle’s diagnostic port and retrieve all stored codes and freeze frame data. Now, write it down and save it for later. Clear the codes and see if the P046B resets.
If the code resets, connect the scanner and observe the data stream with the engine running and at normal operating temperature. You may want to filter the data stream to display only relevant data. This will speed up data delivery and provide you with a more adequate data signal from the exhaust temperature sensor(s) in question.
Obtain the recommended temperature variance specifications for the vehicle in question (from your vehicle information source) and compare them with the actual data (displayed on the scanner’s data stream).
If the scanner data indicates that the difference between the two sensors is not within specifications, use the infrared thermometer to obtain a physical temperature reading. Compare your results with those seen on the scanner’s data display and test the exhaust temperature sensors that do not align.
Use the DVOM to test individual sensors according to the manufacturer’s recommendations. Replace any sensors that do not test within specifications.
Disconnect all associated controllers and test the individual circuits in the system if all sensors are within specifications. Repair or replace any circuits that do not meet the manufacturer’s specifications.
If all sensors and circuits are within specifications, suspect a faulty PCM or a PCM programming error.
A stored P046B code is not a condemnation of a specific catalytic temperature sensor but rather a discrepancy in the correlation between two separate sensors
Suspect PCM failure only after eliminating all other possibilities