P042A Catalyst Temperature Sensor Circuit Malfunction Bank 1 Sensor 2

P042A Catalyst Temperature Sensor Circuit Malfunction Bank 1 Sensor 2

OBD-II DTC Datasheet

Catalyst Temperature Sensor Circuit Malfunction (Bank 1, Sensor 2)

What does this mean?

This Diagnostic Trouble Code (DTC) is a generic transmission code, which means it applies to OBD-II equipped vehicles with a catalyst temperature sensor (Subaru, Ford, Chevy, Jeep, Nissan, Mercedes-Benz, Toyota, Dodge, etc.) D.)). Although it is general, the exact repair steps may vary depending on the make / model.

The catalytic converter is one of the most important parts of the exhaust equipment on a car. Exhaust gases pass through a catalytic converter where a chemical reaction takes place. This reaction converts carbon monoxide (CO), hydrocarbons (HO) and nitrogen oxides (NOx) into harmless water (H2O) and carbon dioxide (CO2).

Converter efficiency is monitored by two oxygen sensors; one is installed before the converter, and the other after it. By comparing the oxygen (O2) sensor signals, the powertrain control module (PCM) can determine if the catalytic converter is working properly. A standard zirconia pre-catalyst O2 sensor rapidly switches its output between about 0.1 and 0.9 volts. A reading of 0.1 volts indicates a lean air/fuel mixture, while 0.9 volts indicates a rich mixture. If the converter is working properly, the downstream sensor should be stable at about 0.45 volts.

Catalytic converter efficiency and temperature are inextricably linked. If the converter is working properly, the outlet temperature should be slightly higher than the inlet temperature. The old rule of thumb was 100 degrees Fahrenheit. However, many modern cars may not show this discrepancy.

There is no real "catalyst temperature sensor". The codes described in this article are for the oxygen sensor. The Bank 1 portion of the code indicates that the problem is with the first bank of the engine. That is, the bank, which includes cylinder # 1. “Sensor 2” refers to a sensor installed downstream of the catalytic converter.

DTC P042A sets when the PCM detects a malfunction in the bank 1 catalyst temperature sensor 2 circuit.

Code severity and symptoms

The severity of this code is medium. Symptoms of a P042A engine code may include:

• Check Engine Light
• Poor engine performance
• Reduced fuel economy
• Increased emissions

reasons

Possible reasons for this P042A code include:

• Defective oxygen sensor
• Wiring problems
• Unbalanced mixture of exhaust air and fuel
• Incorrect PCM / PCM programming

Diagnostic and repair procedures

Begin by visually inspecting the downstream oxygen sensor and associated wiring. Look for loose connections, damaged wiring, etc. Also check for exhaust leaks both visually and audibly. An exhaust leak can cause a false oxygen sensor code. If damage is found, repair as needed, clear the code and see if it returns.

Then check the technical service bulletins (TSBs) for the problem. If nothing is found, you will need to proceed to the step-by-step system diagnostics. The following is a generalized procedure as the testing of this code differs from vehicle to vehicle. To accurately test the system, you need to refer to the diagnostic flowchart for your specific vehicle make / model.

Check for other DTCs

Oxygen sensor codes can often be set due to engine performance issues that cause an imbalance in the air / fuel mixture. If there are other DTCs stored, you will want to clear them first before proceeding with the oxygen sensor diagnosis.

Check sensor operation

This is best done with a scan tool or, better yet, an oscilloscope. Since most people do not have access to the scope, we will look at diagnosing an oxygen sensor with a scan tool. Connect a scan tool to the ODB port under the dashboard. Turn on the scan tool and select Bank 1 Sensor 2 Voltage parameter from the data list. Bring the engine to operating temperature and view the scan tool performance graphically.

The sensor should have a stable reading of 0.45 V with very little fluctuation. If it doesn't respond correctly, it probably needs to be replaced.

Check circuit

The oxygen sensors generate their own voltage signal which is sent back to the PCM. Before proceeding, you need to consult the factory wiring diagrams to determine which wires are which. Autozone offers free online repair guides for many vehicles, and ALLDATADIY offers a single car subscription. To test for continuity between the sensor and the PCM, turn the ignition key to the off position and disconnect the O2 sensor connector. Connect a DMM to the resistance (ignition off) between the O2 sensor signal terminal on the PCM and the signal wire. If the meter reading is out of tolerance (OL), there is an open circuit between the PCM and the sensor that needs to be located and repaired. If the counter reads a numeric value, there is continuity.

Then you need to check the grounding of the circuit. To do this, turn the ignition key to the off position and disconnect the O2 sensor connector. Connect a DMM to measure the resistance (ignition off) between the ground terminal of the O2 sensor connector (harness side) and chassis ground. If the meter reading is out of tolerance (OL), there is an open circuit on the ground side of the circuit that must be found and repaired. If the meter shows a numeric value, there is a ground break.

Finally, you will want to check if the PCM is processing the O2 sensor signal correctly. To do this, leave all connectors attached and insert the rear sensor test lead into the signal terminal on the PCM. Set the DMM to DC voltage. With the engine warm, compare the voltage reading on the meter to the reading on the scan tool. If they do not match, the PCM is probably defective or needs to be reprogrammed.

Related DTC discussions

• Opel Astra P042AOPEL ASTRA H, type AH / SW / FX11 / ASTRA STATION WAGON, 1.7 cc engine See Model A17DTR Error Code P042A ... 

Need more help with code p042A?

If you still need help regarding DTC P042A, post a question in the comments below this article.

NOTE. This information is provided for informational purposes only. It is not intended to be used as a repair recommendation and we are not responsible for any action you take on any vehicle. All information on this site is protected by copyright.