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Error Code P046B is defined as Catalyst Temperature Sensor 1/2 Correlation Bank 2. This means there’s a discrepancy between the temperature signals from the catalytic converter of the engine bank 2.
This code is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II, especially those made in 1996 up to the present. It is common among Chevrolet, Dodge, Ford, Ram, etc. Specifications on the definition, troubleshooting and repairs, of course, vary from one make and model to another.
Bank 2 signifies the bank of the engine that does NOT contain the #1 cylinder. Only diesel applications utilize catalyst temperature sensors.
To cleanly burn diesel, vehicles are equipped with different types of diesel exhaust ignition to clear the catalytic converter from harmful emissions. DEF or diesel exhaust fluid, is injected into the catalytic converter to increase the temperature of the catalytic converter and burn off the particles of nitrogen oxide that are trapped within. These vehicles use catalyst temperature sensors (rather than O2 or oxygen sensors) to monitor the efficiency of the catalytic converter. The most efficient and practical way to monitor catalyst efficiency is temperature.
Sensor 1 and Sensor 2 are also called the upstream and downstream catalyst sensors, respectively. These sensors are placed just before and right after the catalytic converter in the exhaust system. As the engine runs and warms up sufficiently, exhaust entering the catalytic converter should be cooler than the exhaust exiting the converter. This is regardless of the DEF system’s state. The PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) monitors the temperature sensors of the catalyst and compares the two sensor signals. If the degree of difference between the two is outside the programmed about, then the Error Code P046B will be stored, and the Check Engine light will be activated.
As with other error codes, the Check Engine light will be activated, and the code will be stored in the vehicle’s computer system, other symptoms include:
- Increase in fuel consumption
- Increase in exhaust emissions
- Heavy black smoke from the exhaust
Other DEF and catalytic codes may also be present.
Common causes for Error Code P046B include:
- Defective exhaust temperature sensor
- DEF system malfunction
- Malfunctioning catalytic converter
- Burned, open, or shorted circuits in the exhaust temperature sensor system
How to Check
To diagnose this code, technicians use a diagnostic scanner, a DVOM (digital volt/ohmmeter), infrared thermometer (with laser pointer if possible), and a dependable vehicle information source.
Technicians ensure the DEF system is filled with the correct fluid and working properly. If there are other DEF related codes present, it’s highly advisable to address these other codes first and repair them before diagnosing P046B. Technicians will then inspect all connectors and wirings related to the suspect system. They focus on harnesses routed near hot exhaust pipes and manifolds.
Then they connect the scanner to the vehicle’s diagnostic port to retrieve all stored codes and the freeze frame data of the P046B. They take note of the data for later. Then they clear the code and see if the code reset.
If the code reset, then they connect the scanner and observe the data stream with the engine running at normal operating temperature. They usually narrow the data stream, so it only displays pertinent data and speeds up the delivery to provide more adequate data signal from the exhaust temperature sensor(s) in question.
Next, they get the temperature variance recommendation for the vehicles in question (from the vehicle information source) and compare them with the actual data (which is displayed on the data stream of the scanner).
If the difference between the sensors is outside the specifications, then they use the infrared thermometer to get the physical temperature. Then they compare their results with those seen on the scanner data display and test the exhaust temperature sensors that don’t align.
Next, Technicians use the DVOM to test the individual sensors according to the recommendations set by the manufacturer. Sensors that don’t test within the specs must be replaced.
Next, technicians will have to disconnect all related controllers and test the individual circuits if all the sensors are within the specifications. Circuits that don’t comply with the specifications set by the manufacturer must be repaired, if not replaced.
If all the circuits and sensors are inside the specifications set by the vehicle’s manufacturer, then the problem must be caused by a defective PCM or an error in its programming.
How to Fix
As said in the diagnosis, common repairs include:
- Diagnosis and repair of other related DEF codes first
- Replacement of faulty sensors
- Repair or replacement of defective circuits
- Replacement and reprogramming of the PCM
Note that a stored Error Code P046B is not a commendation of any particular catalyst temperature sensor, but a discrepancy between the correlation of the two separate sensors.
If after all the diagnosis you still can’t eliminate the code, then the code is most likely caused by a fault in the PCM.