When to change the oxygen sensor on a catalytic converter?

To illustrate, many DIYers and professional mechanics might believe that changing an oxygen sensor will turn off the “check engine” light on a vehicle with a defective catalytic converter. Others believe that the catalytic converter must always be replaced when a P0420 or P0430 diagnostic trouble code is stored.

What happens when a catalytic converter becomes defective?

When a catalytic converter becomes defective, the signal from the rear oxygen sensor begins to duplicate the switching signal of the front oxygen sensor. The PCM then uses a mathematical algorithm to determine when the downstream signal exceeds FTP standards.

Why is my catalytic converter reading lean 0.1v?

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. The ECM would interpret that as a bad catalytic converter. In that case, your OBDII scanner should be reading a lean 0.1v reading from the downstream sensor.

What should the OBDII reading be on a bad catalytic converter?

The ECM would interpret that as a bad catalytic converter. In that case, your OBDII scanner should be reading a lean 0.1v reading from the downstream sensor. You can add propane fuel to the exhaust to force the reading up to prove that the downstream sensor is good.

What is a bad O2 sensor?

Bad O2 sensors are one of those car problems that most drivers tend to postpone until more serious problems occur. These symptoms will rarely cause any immediate damage, but over time, if left unattended, they can cause damage to the engine and other systems mainly through improper air-fuel mixture.

What does a catalytic converter OBD II mean?

What does a Catalytic Converter OBD II mean? OBDII (On Board Diagnostics II) systems are required by Federal law on all passenger cars and light trucks manufactured since 1996. It is a computer on board the vehicle that monitors the engine and emission control equipment to verify that all systems are working properly.

What is a good oxygen sensor reading?

The primary O2 sensor reading should range between 300-600mV sometimes going as low as 100 mV and as high as 900 mV and the reading will change quickly.

What is a catalytic convertor?

A catalytic converter is an exhaust emission control device that reduces toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction (an oxidation and a reduction reaction). Catalytic converters are usually used with internal combustion…