P0420 Code Gmc Acadia (2024)

FAQs

P0420 Code Gmc Acadia? ›

P0420 stands for “Catalyst System Efficiency Below Threshold (Bank 1).” This trouble code is triggered when the on-board computer detects that the bank 1 of the catalytic converter is underperforming.

How Serious Is the P0420 Code? Driving your car with the P0420 code will only lead to further damage to the catalytic converter.

The most common cause is a damaged or faulty oxygen sensor. There are two oxygen sensors in the exhaust that feed information back to the ECU (Engine Control Unit). If one isn't working correctly, then the ECU won't be able to control the air/fuel mixture properly, so it throws up the P0420 fault code.

Cracking the Code

A common emissions code seen in the field, a P0420 trouble code indicates that the catalytic converter isn't functioning efficiently. To work at peak efficiency, the emissions or feed gases entering the catalytic converter need to be perfectly balanced and not excessively elevated.

A catalyst monitor uses signals from the downstream O2 sensor to determine catalyst efficiency. It uses signals from the upstream O2 sensor as a reference point. If any or both of these oxygen sensors fail, they can trigger the P0420 code.

The cost of repairing DTC P0420 varies greatly depending on the diagnosis. If it's just a minor exhaust leak, you might be able to weld the holes yourself for next to nothing. Catalytic converters, on the other hand, can be costly. Essentially, P0420 repairs might cost anywhere from $10 to $2,000 or more.

P0420 means a catalytic converter problem affecting its efficiency or a problem with the oxygen sensors. So yes, it could be a bad plug which is allowing unburnt fuel to enter the cat and eventually damaging it.

This has nothing to do with the gas cap.

Impact of a P0420 Code on Vehicle Performance and Emissions

A rotten egg smell coming from the exhaust pipe is another common symptom. While engine fault code P0420 is not a serious, immediate threat to safe driving, it can lead to worsening problems with the vehicle's performance.

It is unlikely that this code will be set by itself. If there are no other trouble codes, then check your engine oil and coolant levels first. If they are low, it indicates that they are either leaking externally or being burned in the engine. The next step to check are the oxygen sensors.

How do I know if I have a bad O2 sensor or catalytic converter? ›

You need an OBDII reader to tell you which sensor is bad. You may have 2 or 4 sensors, depending upon whether you have a 4 cylinder, V6 or V8. When the 02 sensor goes bad, it will plug up the catalytic converter. So as soon as you know it's an 02 sensor it needs to get replaced.

Soaking: One method to try is submerging and soaking the catalytic converter in a soapy water solution. A dedicated oil or degreaser product will probably work best, though you might also try dish soap. Add your cleaner to a sufficiently large bucket of water where the converter can fit.

While you can technically still drive your car with a P0420 code, it's not recommended to do so for an extended period. Ignoring this code can lead to reduced fuel efficiency, higher emissions, and potentially more significant damage to the engine or the catalytic converter.

Fortunately, a product like the Rislone Cat Complete Fuel, Exhaust and Emissions System Cleaner 16.9oz can help switch that light off and clean out the soot, carbon build-up, and residue in your fuel system.

That could be due to an excessively rich fuel mixture, a leaking fuel injector, or a compression/engine timing issue that won't burn the fuel correctly. If you're seeing correct readings from the oxygen sensors, try playing around with the fuel mixtures and see if the engine computer is able to compensate correctly.

Some products claim to clean the catalytic converter and revitalize it. What the cleaners actually do is remove carbon deposits from various components in the fuel and exhaust systems. These cleaners may be effective enough to cause a boost in performance, but the problem of the clogged cat probably won't change.