Additionally, once the 160º F threshold is achieved, the recorded engine temperature must not fall below 160º F during operation. Most PCMs mandate that the engine coolant temperature sensor record temperatures above 160º F within 15 minutes of the engine starting. When the correct engine operating temperature is reached, the powertrain control module orders the fuel system to enter “closed loop” where readings from the oxygen sensors are used to maintain the efficient air to fuel ratio of 14.7:1. The powertrain control module (PCM) tracks how long it takes for the engine of your Hyundai to reach and maintain the correct operating temperature. If the voltage of the downstream O2 sensor is constantly jumping between 0.1V and 0.9V, the catalyst is worn and the catalytic converter needs to be replaced.Coolant thermostat temperature below regulating temperature Hyundai Code P0128 Meaning The downstream O2 sensor produces a relatively steady voltage reading of approximately 0.45V if the catalytic converter is functioning properly. With the Hyundai running and at normal operating temperature, use the digital multimeter to check the voltage reading of the downstream O2 sensor.If any leaks are found, repair the leak, clear the code, and complete several drive cycles to verify that was the fix. Pay close attention to the exhaust manifold, gaskets, and exhaust pipes pre-catalytic converter.

Examine the exhaust system for damage and leaks.

If other codes are present, they must be addressed first.

Scan your Hyundai to verify P0420 is the only code present.

Hyundai P0420 Diagnosis Tools Needed to Diagnose: If any other codes are present, they should be addressed first. Hyundai Code P0420 Common Diagnosis Mistakesĭo not overlook other codes that are paired along with P0420. It is recommended that you address P0420 as soon as possible to keep the cost of the repair to a minimum. While P0420 does not pose a danger to the driver and may not produce any symptoms with issues related to drivability, it can cause severe damage to other components of your Hyundai if not addressed in a timely manner.

Worn and internally failing catalytic converter.

Code P0420 indicates that the catalytic converter is not functioning efficiently, therefore increasing the output of harmful pollutants by your Hyundai.

The function of the catalytic converter is to break down harmful pollutants that are created by your Hyundai during the combustion cycle and convert them into harmless gases. Catalyst system efficiency below threshold (Bank 1).

Hyundai check engine light causes