P042A OBD Error Code: Problem & Solutions

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The OBD Code P042A can be defined as Catalyst Temperature Sensor Circuit Malfunction Bank 1 Sensor 2. A number of temperature sensors are used by the catalytic converter to ensure that the catalytic converter does not overheat and is working efficiently. If an incorrect signal is determined from the catalytic converter temperature sensor by the engine control module, then the powertrain control module would start flashing the P042A trouble code

The performance of the catalytic converter temperature sensor circuit is monitored by the engine control module which performs the function of measuring the temperature of the catalyst. The catalyst temperature sensor functions by increasing their resistance with increasing the temperature of the exhaust gas. The ECM will then set the error code when the catalyst temperature sensor signal is not as per the factory specifications.

What causes this problem with the Catalyst Temperature Sensor Circuit Malfunction Bank 1 Sensor 2?

• Issues related to wiring
• The PCM/PCM programming can be defective
• There can be some faults in the oxygen sensor
• Catalyst temperature sensor harness might be opened or shorted
• Exhaust air/fuel mixture might be out of balance
• Flaws in the catalyst temperature sensor
• There can be poor electrical connection in the catalyst temperature sensor circuit

1. Catalytic Converter - Did your mechanic just found out that there is some fault in the Catalytic Converter? Buy top notch Catalytic Converter from us at economical prices.
2. Powertrain Control Module - A broken Powertrain Control Module can cause a lot of issues. It would be nice if you get it replaced on time.
3. Oxygen Sensor - Everything is fine with the engine control module and still OBD code P042A flashing? Then there is definitely some fault with the Denso Oxygen Sensor. Get it checked and replace if needed.
4. Exhaust System Parts - Exhaust System Parts should never be neglected. May be there is some fault in them due to which P042A code may start flashing.
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6. Air Fuel Ratio Sensor - If everything is alright with PCM, then there is surely some defect in Air Fuel Ratio Sensor. Get it replaced before the situation gets worse.
7. Engine Control Module - P042A code can display due to some faults in the Engine Control Module. So, it is very important to replace the Engine Control Module with us at equitable prices.

Our main motive is to achieve customer satisfaction as for us our customers are everything and that’s why we will help you to diagnose P042A code by mentioning some major symptoms below:

Common Symptoms

• The check engine light can start flashing
• The engine performance might be bad
• Diminishing fuel economy
• Increase in the overall emissions

If you wish to correct this fault code, then you have to follow certain steps. Correcting a problem needs your careful attention. Here are some ways with the help of which you will be able to correct the OBD Code P042A:

• If there are some faults in the wiring, then you can always get it repaired
• The programming error in the PCM can cause a lot of issues, so it would be better to get it restored
• Replace the catalyst temperature sensor
• Make sure that the electrical connection in the catalyst temperature sensor circuit is checked and you can always correct it as per the need

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Here are some steps which you should follow in order to diagnose this fault code:

You can always begin by visually inspecting the downstream oxygen sensor and the corresponding wiring. Look for loose connections, damaged wiring, etc. You should also inspect for exhaust leaks both visually as well as audibly. A false oxygen sensor code can be cause due to an exhaust leak. If damage is found, repair as necessary, clear the code and see if it returns.

The next step would be to check for technical service bulletins regarding the issue. If nothing is found, you will need to move forward to step by step diagnosis of the system. The following is a generalized procedure, as testing for this code varies between vehicles. To accurately test the system, you can always refer to a vehicle make/model specific diagnostic flow chart.

Check for other DTCs

Oxygen sensor codes can often be set because of engine performance problems that cause an out of balance air/fuel mixture. If there are other DTCs stored, you can always address those first before proceeding with oxygen sensor diagnosis.

Check Sensor Operation

This is best done using a scan tool, or better yet, an oscilloscope. Since most individuals don't have access to a scope, so we will cover oxygen sensor diagnosis using a scan tool. Connect the scan tool to the OBD port under the dash. Turn the scan tool on and choose the Bank 1 Sensor 2 voltage parameter from the data list. Bring the engine up to operating temperature and view the sensor operation on the scan tool in graph mode.

The sensor should have a steady 0.45 volt reading with only very small fluctuations. If it is not responding correctly then it should be replaced.

Check the circuit

Oxygen sensors produce their own voltage signal which is sent back to the PCM. Before proceeding, you can always consult the factory wiring diagrams to determine which wires are which. To check for continuity between the sensor and PCM, turn the ignition key to the "off" position and disconnect the O2 sensor connector. Connect a digital multimeter set to ohms with the ignition off between the O2 sensor signal terminal on the PCM and the signal wire. If the meter reads out of limits (OL) there is an open circuit between the PCM and sensor that will need to be located and repaired. If the meter reads a numeric value, it means that 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 (with the ignition 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 numeric value, there is continuity to ground.

Finally, you should check that the PCM is processing the O2 sensor signal properly. To do this, leave all the connectors attached and insert a back-probe meter lead into the signal terminal at the PCM. Set the digital multimeter to the DC volts setting. With the engine warmed up, compare voltage reading on the meter to that on the scan tool. If the two do no match, the PCM is likely faulty and there is a need to reprogram the powertrain control module.

Common Mistakes When Diagnosing The P042A Code

• Failure in the catalytic converter temperature sensor
• Powertrain control module might have some flaws
• There can be some issues related to wiring