Contents
What can cause an O2 sensor to throw a code?
Deceptive Oxygen Sensor Codes
- An inefficient catalytic converter.
- Engine vacuum leaks that create a lean exhaust condition.
- Mass airflow sensor failure that creates a rich exhaust condition.
- Manifold air pressure sensor failure that creates a rich exhaust condition.
What codes will a bad catalytic converter cause?
Usually, an illuminated check engine light is the first and only sign of a bad catalytic converter. When the light pops on, your car’s engine control module (ECM) will also store a diagnostic trouble code (often a P0420 code) in its memory.
How do I know if my O2 sensor is bad?
Here are some of the most common signs that your oxygen sensor is bad.
- A Glowing Check Engine Light. The bright orange Check Engine light in your dashboard will usually glow if you have a bad oxygen sensor.
- Bad Gas Mileage.
- An Engine That Sounds Rough.
- An Emissions Test Failure.
- An Older Vehicle.
Can a post Cat O2 sensor be faulty?
As these two graphs show, the post-cat barely crosses 0.6V; it doesn’t cross 0.5V. Is this an indication of a faulty post-cat O2 sensor? Your graphs look very normal. No, the post cat sensor will remain a nearly flat line when the engine is a steady speed, if the catalyst is good.
Can a bad O2 sensor cause a P0420 code?
Can a bad O2 sensor cause a P0420 code? Yes. A typical catalyst monitor uses the signal from the downstream oxygen sensor to determine catalyst efficiency, and the signal from the upstream sensor is a reference point. As such, failure of either the upstream or downstream oxygen sensor can cause code P0420 to set.
Why is the rear O2 sensor behind the light-off catalyst lazy?
The O2 sensor behind the light-off catalyst (the Downstream Sensor) is also monitoring oxygen, but if the light-off (NOx) catalyst is storing oxygen properly (meaning the catalyst is healthy), the rear O2 sensor signal will be very lazy when compared to the upstream O2.
Why is my OBD not working on my catalytic converter?
The OBD II system can’t evaluate the converter if the upstream and downstream O2 sensors are not functioning normally. So any O2 sensor problems have to be dealt with before you can use the OBD II system to diagnose the converter. O2 sensors typically fail because of old age or contamination.