Error Code P0429: What It Means & What To Do?

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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.

This trouble code is generic, which would mean that it can apply to all the vehicles which are equipped with the OBD-II or the vehicles which are made since 1996 up to the present. The specifications on the definition, the troubleshooting steps as well as repairs can always vary from one vehicle make to another.

This can happen because of a lot of reasons and the mechanic should diagnose the specific cause for this code.

What causes this problem with the Catalyst Heater Control Circuit?

• Defaults in the oxygen sensor
• Catalyst Temperature Sensor circuit might have bad electrical connection
• The PCM/PCM programming might be quirky
• The catalyst temperature sensor might have some defects
• Problems related to wiring
• The exhaust air/fuel mixture can be out of balance
• There can be opened or shorted catalyst temperature sensor harness

1. Catalytic Converter - Defective car Catalytic Converter can be a major reason why P0429 code depicts. So, make sure to replace it online so that you don’t have to face any further issues.
2. Engine Control Module - Everything is okay with the Air Fuel Ratio Sensor and still OBD code P0429 triggering? Then there must be some defects in Engine Control Module. Replace them as soon as possible.
3. Air Fuel Ratio Sensor - P0429 code flashing? Get your Air Fuel Ratio Sensor inspected from a mechanic.
4. Oxygen Sensor - If everything is alright with PCM, then there is surely some defect in Denso Oxygen Sensor. Get it replaced before the situation gets worse.
5. Exhaust System Parts - P0429 code can display due to some faults in the Exhaust System Parts. So, it is very important to replace the Exhaust System Parts with us at equitable prices.
6. Powertrain Control Module - Do you remember when was the last time you got your car Powertrain Control Module checked up? A faulty Powertrain Control Module can cause a lot of issues like displaying P0429 code.
7. Diagnostic Tool - Willing to buy new Car Diagnostic Tools? You can always rely on us as we have best Automotive Diagnostic Tools for our customers.

You might be thinking that how would you diagnose these problems? We at Parts Avatar Canada would help you diagnose the major symptoms easily.

Common Symptoms

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

The repairs which you will have to do to correct this fault code are simply straightforward; you can surely pinpoint the necessary repairs on the basis of your diagnosis. Have a look at some common fixes:

• The defective wiring should be repaired or replaced properly
• A lot of problems can be caused due to programming error in the PCM, so you can always replace it
• Restore the quirky catalyst temperature sensor
• Inspect the electrical connection in the catalyst temperature sensor circuit

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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 P0429 Code

• Catalytic converter temperature sensor might start failing
• Quirks in the powertrain control module
• Problems related to wiring