Symptoms

- Engine Light ON (or Service Engine Soon Warning Light)

Possible Causes

- Catalytic Converter defective - Engine misfire or running condition. - Large vacuum leak - Engine oil leakage into exhaust- valve guide seals, piston rings.

When Detected

The P0421 code is triggered when PCM has determined that the warm up catalyst efficiency for bank 1 is below threshold for the current engine operating condition. (Bank 1 identifies the location of cylinder #1, while bank 2 identifies the cylinders on the opposite bank)

Tech Notes

Mitsubishi issue a Service Recall for this problem. Contact you local Mitsubishi dealer

Description

The oxygen sensors monitor the catalytic converters ability to store oxygen.