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P0429 is a diagnostic trouble code (DTC) for "Catalyst Heater Control Circuit". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.
The P0429 code pertains to improper operation of your heated oxygen sensors. It signifies that both sensors have malfunctioned in some way.
Your vehicle’s ECM (Engine Control Module) tracks the switching frequency ratio of the dual heated oxygen sensors. There are oxygen sensors one, which are your front O2 sensors, and heated oxygen sensors 2, which are the O2 sensors to your rear. When your vehicle is operating correctly, these two sensors work in tandem.
A catalyst converter with a high capacity for oxygen storage will indicate when there is a low switching frequency of the rear O2 sensor (heated oxygen sensor 2). As the storage capacity for oxygen decreases, that rear sensor’s switching frequency will do the opposite (it goes up) As it increases in capacity, it and the other oxygen sensor may eventually reach a predetermined limit value. When that happens, a malfunction in the catalyst is diagnosed and the P0429 code is stored by your ECM.
There are three main culprits that may be responsible for P0429:
Usually, the Check Engine light should come on, letting you know something is wrong. Depending on the fallout from this problem, your ECM may actually detect the O2 sensor heater circuit is low and activate failsafe mode. If this happens, you’ll need to turn the ignition off. Failsafe mode won’t go away until the original problem is addressed.
You may also notice that your vehicle runs a bit rough or even has a hard time accelerating.
To diagnose this problem, your mechanic will need to use an OBD-II scanner. Usually, they’ll initiate a reset and then take the vehicle out on a test drive to see if the code reappears. If that happens, the mechanic will proceed to checking the power and ground to the sensor. This will include a complete examination of the wiring and sensor. Due to the extreme heat of the catalytic converter and exhaust, it is very important to check all the wiring.
As we just mentioned, the wiring often gets damaged because of how hot it is next to these components, so it’s very likely that a simple repair can clear P0429 for good. This makes it all the more unfortunate when mechanics don’t do a thorough inspection and simply move onto expensive/unnecessary repairs.
Though it’s not going to put your life at risk, this type of problem is extremely frustrating as it can greatly hinder the performance of your car and even force you to spend more at the pump.
Your mechanic will most likely do one of the following to attack this problem.
It’s not unheard of for code P0429 to be accompanied by a number of others. If that’s the case for your vehicle, it would be wise to address those other codes first and then deal with this one. That will often do the trick or at least make it much clearer what has to happen to repair code P0429.
YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.