P0435 code definition
This Diagnostic Trouble Code (DTC) is the generic code for Catalyst Temperature Sensor Bank 2, indicating that the problem originates from the engine bank which does not contain cylinder #1.
What the P0435 code means
In order to determine proper exhaust composition and temperature, the Powertrain Control Module (PCM) analyzes data sent from the oxygen sensors, using the data to calculate catalyst efficiency. If the signal sent to the PCM by the oxygen sensors falls outside of the expected parameters, the code will set.
What causes the P0435 code?
The most likely causes of this code are a faulty catalytic converter or bad oxygen sensors. Catalytic converters can fail due to:
- Fuel in the exhaust system
- Improper fuel usage
- A faulty mass airflow (MAF) sensor
- Fuel injector malfunction
- A faulty fuel regulator
- A coolant temperature sensor malfunction
- A damaged or leaking flex hose
- Faulty spark plug timing
What are the symptoms of the P0435 code?
The signs of this problem can range from just the stored DTC and a lit Check Engine Light, to engine stalling or a no-start condition. If faulty O2 sensors or a catalytic converter operating below the optimal efficiency threshold are the issue, you will probably still be able to drive the vehicle. If the catalytic converter is broken, however, you may experience poor engine performance, hissing noises, or the inability to start the vehicle.
How does a mechanic diagnose the P0435 code?
Diagnostic procedures could include:
- Scanning the vehicle’s computer and capturing the data, including any concurrent codes
- Clearing the DTCs and road testing the vehicle to ensure it’s not an intermittent condition
- Measuring the temperature of the exhaust pipe before and after the catalytic converter, using a temperature gun (preferably equipped with a laser pointer)
- Using a scanner and oscilloscope to monitor oxygen sensor function
- Inspecting sensor wiring and connections
- Visually inspecting the catalytic converter
Under normal conditions, when the engine has been test driven and is allowed to idle at normal operating temperature, the upstream O2 sensor should fluctuate quickly between .350 and .900 volts. The downstream sensor should stay around .500 volts. If these reactions are slower than expected, or nonexistent, the O2 sensors could be faulty. If the downstream sensor fluctuates close to the way the upstream sensor does, it could be a bad catalytic converter.
Common mistakes when diagnosing the P0435 code
The most common error is to replace the O2 sensors before verifying that they are malfunctioning. This is often done to try to avoid replacing the (expensive) catalytic converter; however, it may not solve the problem.
Another mistake is not addressing concurrent DTCs, which if left unchecked could trigger repeated catalytic converter failure.
How serious is the P0435 code?
The severity of this issue really depends upon the source of the problem. Catalytic converter failure may eventually affect engine performance, causing further damage. It can also cause problems with emissions testing if this is required in your state.
What repairs can fix the P0435 code?
Potential repairs include:
Additional comments for consideration regarding the P0435 code
It’s always advisable to diagnose and repair any other DTCs present along with the current issue, but it’s especially important in this case. There may be other O2 sensor, fuel mixture, fuel trim, or misfire codes and these should be addressed before assuming the repair is complete.
Due to the fact that the vehicle will likely need to be lifted in order to diagnose and repair P0435, your best bet is to have your car checked by a qualified technician who has the tools, equipment, and expertise to efficiently identify the problem and get you back on the road.
Need help with a P0435 code?
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