What O2 sensor voltage would indicate a lean condition?
More oxygen in the exhaust than optimal results in a signal voltage under 450 mV. This reflects a LEAN CONDITION. Good oxygen sensors have even waves in the 150 mV to 850 mV range while ascending or descending within a 100 mS or less when the system is in closed loop.
Which oxygen sensor checks the efficiency of the catalytic converter?
catalyst efficiency monitor
The catalyst efficiency monitor verifies that the catalytic converter is operating at a high enough efficiency rating to keep exhaust emissions within predetermined values. The PCM compares the signals from the upstream and downstream oxygen sensors to determine the state of the converter.
How are O2 sensors and catalytic converter diagnostics fail?
O2 SENSORS & CATALYTIC CONVERTER DIAGNOSTICS Converters typically fail one of two ways: they get too hot, melt and plug up, or the catalyst becomes contaminated and useless.
What does P0420 mean on a catalytic converter?
Here’s the official definition of a P0420 trouble code: P0420 Catalyst System Efficiency Below Threshold (Bank 1). What the code is telling you is that the catalytic converter has failed an efficiency test. In 99.5% of the cases, this code means that the catalytic converter itself is bad and must be replaced.
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.
When does an O2 sensor set a trouble code?
If it’s not switching rapidly, the ECM will set an O2 sensor related trouble code 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.