What does a P0420 diagnostic trouble code mean?
A P0420 diagnostic trouble code is a “generic” fault code that is set when the Onboard Diagnostic II (OBD II) catalyst monitor detects a drop in converter efficiency. The OBD II system monitors catalyst efficiency by comparing the switching activity of the upstream and downstream oxygen sensors in…
Why is my catalytic converter code a false P0420?
You may have a false P0420 if your vehicle’s catalyst monitor is overly sensitive. Some vehicle manufacturers have issued Technical Service Bulletins (TSBs) that involve reflashing the vehicle’s engine computer so the catalyst monitor won’t be quite and sensitive and slower to fail an aging converter.
How does the PCM know when to cut back on fuel?
To check on how well it did calculating the air/fuel mixture, it checks the readings from upstream oxygen sensors (O2). If the readings shows the exhaust is rich, the PCM will cut back on fuel. If the reading is too lean, it’ll add fuel.
Where does the P0420 trouble code come from?
P0420 is triggered in the engine control module when there is a problem with the efficiency of the catalytic converter. The engine control unit uses two O2 sensors, one in the front of and one behind the catalytic converter to measure the efficiency of the catalytic converter.
What causes the O2 sensor to show the code po420?
Rich or lean mixtures can damage the catalytic converter, and when the catalytic converter is damaged/filled with fuel, the efficiency will be low, and the rear O2 sensor will see that and show the trigger the code Po420.
Can a damaged catalytic converter trigger the code po420?
Yes, they can, but not in the way you think. Rich or lean mixtures can damage the catalytic converter, and when the catalytic converter is damaged/filled with fuel, the efficiency will be low, and the rear O2 sensor will see that and show the trigger the code Po420.
Why do I need to resolve the P0300 code first?
For example, if you have these codes – P0300, P0420, P0171, then you’re going to want to tackle the P0300 Random Misfire code first (resolve it), and then tackle the P0420 code, etc. The reason for that is that the first code could be causing further DTCs to be set.