Are pre cat and post cat O2 sensors the same?
“Whilst the pre-cat lambda sensor communicates to the ECU regulating the air/fuel ratio; the post-cat lambda sensor performs a diagnostic role, monitoring the catalytic converter.
What is the purpose of the post catalyst oxygen sensor?
The signal from the pre-catalyst oxygen sensor is primarily responsible for air-fuel mixture adjustments, while the post-catalyst oxygen sensor signal monitors the performance of the catalytic converter and the amount of oxygen being absorbed during its operation.
Where do I find the O2 sensor on my car?
Look for the oxygen/o2 sensors now. These usually look like plugs that protrude out of the engine’s exhaust system. Each of these is typically found at the rear and the front of the catalytic converter. Carefully, unhinge the electrical wire that’s embedded within the sensor.
Why are the oxygen sensors after the cat?
Also post catalyst oxygen sensor is after the cat not before… A misfire in which the fuel injector injects a mixture that is too lean to ignite will result in both oxygen sensors seeing a lean mixture. This will result in the sensor output of little or no voltage.
When to use post O2 sensor in catalytic converter?
So the article is telling you to use the post O2 sensor reading to determine if the misfire is due to a lack of fuel (clogged fuel injector, vacuum leak, etc), or too much fuel (spark plug didn’t fire so none of the fuel was ignited and is now being burned in the cat instead of the cylinder.
What causes the P0420 oxygen sensor to read lean?
If the upstream and downstream oxygens sensors are both switching from rich to lean, that’s the sign of a dead catalytic converter. An exhaust system leak really screws up the P0420 testing routing. An exhaust leak near the upstream sensor can cause the downstream sensor to read a steady lean condition.