What does it mean?
This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to OBD-II equipped vehicles that have a catalyst temperature sensor (Subaru, Ford, Chevy, Jeep, Nissan, Mercedes-Benz, Toyota, Dodge, etc.). Although generic, the specific repair steps may vary by make/model.
The catalytic converter is one of the most important emission devices on a vehicle. Exhaust gases pass through the catalytic converter where a chemical reaction occurs. This reaction converts carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) into harmless water (H2O) and carbon dioxide (CO2).
The converter’s efficiency is monitored by two oxygen sensors; one mounted upstream of the converter and one mounted downstream. By comparing the signals from the oxygen (O2) sensors, the powertrain control module (PCM) can determine if the catalytic converter is functioning properly. A standard zirconia pre-catalyst O2 sensor will rapidly switch its output signal between approximately 0.1 and 0.9 volts. A reading of 0.1 volt indicates a lean air/fuel mixture, while 0.9 volt indicates a rich mixture. If the converter is working correctly, the downstream sensor should read steadily around 0.45 volts.
The catalytic converter’s efficiency and temperature go hand in hand. If the converter is operating as it should, the outlet temperature should be slightly higher than the inlet. The old rule of thumb was a 100-degree Fahrenheit difference. However, many modern vehicles might not show that much difference.
There is no actual “catalyst temperature sensor.” What the codes in this article refer to is the oxygen sensor. The “bank 2” part of the code indicates the issue is from the engine’s second bank. That is, the bank that does not include cylinder number 1. “Sensor 2” refers to the sensor mounted downstream of the catalytic converter.
Trouble code P043D is set when the PCM detects a high catalyst temperature sensor signal in bank 2, catalyst temperature sensor 2 circuit. This typically indicates an open circuit.
Code Severity and Symptoms
The severity of this code is moderate. Symptoms of a P043D engine code may include:
Check Engine Light illuminated
Poor engine performance
Reduced fuel economy
Increased emissions
Causes
Possible causes of this P043D code include:
Faulty oxygen sensor
Wiring issues
Unbalanced air/fuel mixture
PCM programming / faulty PCM
Diagnostic and Repair Procedures
Start by visually inspecting the downstream oxygen sensor and its associated wiring. Look for loose connections, damaged wiring, etc. Also check for exhaust leaks visually and audibly. An exhaust leak can cause a false oxygen sensor code. If damage is found, repair as necessary, clear the code, and see if it returns.
Next, check for Technical Service Bulletins (TSBs) regarding the issue. If nothing is found, you’ll need to move on to step-by-step diagnosis of the system. The following is a generalized procedure, as tests for this code vary by vehicle. To accurately test the system, you will need to refer to a diagnostic flowchart specific to the vehicle’s make/model.
Check for Other DTCs
Oxygen sensor codes can often be set due to engine performance issues causing an unbalanced air/fuel mixture. If other trouble codes are stored, you should address those first before proceeding with oxygen sensor diagnosis.
Check Sensor Operation
To do this, it’s best to use a scan tool or, even better, an oscilloscope. Since most individuals do not have access to an oscilloscope, we will cover diagnosing the oxygen sensor using a scan tool. Connect the scan tool to the OBD port under the dashboard. Turn on the scan tool and choose the Bank 2 Sensor 2 voltage parameter from the data list. Bring the engine to operating temperature and view the sensor’s operation on the scan tool in graph mode.
The sensor should have a steady reading of 0.45 volts with only very small fluctuations. If it does not respond correctly, it will likely need to be replaced.
Check the Circuit
Oxygen sensors produce their own voltage signal that is sent back to the PCM. Before proceeding, you’ll want to consult factory wiring diagrams to determine which wires are which. Autozone offers free online repair manuals for many vehicles, and ALLDATADIY offers single-vehicle subscriptions. To check continuity between the sensor and the PCM, turn the ignition key to the “off” position and disconnect the O2 sensor connector. Connect a digital multimeter set to ohms (power off) between the PCM’s O2 sensor signal terminal and the signal wire. If the meter reads out of limits (OL), there is an open circuit between the PCM and the sensor that will need to be located and repaired. If the meter reads a numerical value, there is continuity.
Next, you’ll want to check the ground side of the circuit. To do this, turn the ignition key to the “off” position and disconnect the O2 sensor connector. Connect a digital multimeter set to ohms (power off) between the O2 sensor connector ground terminal (harness side) and chassis ground. If the meter reads out of limits (OL), there is an open circuit on the ground side of the circuit that will need to be located and repaired. If the meter reads a numerical value, there is continuity to ground.
Finally, you’ll want to verify that the PCM is processing the O2 sensor signal correctly. To do this, leave all connectors connected and insert a back-probing pin into the PCM’s signal terminal. Set the digital multimeter to the DC volts setting. With the engine warmed up, compare the voltage reading on the meter to that on the scan tool. If the two do not match, the PCM is likely faulty or requires reprogramming.