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Home >> Jeep >> 2025 >> Grand Cherokee Altitude, AWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 35 (2.0L - DTCS P040B To P0463) >> DTC Troubleshooting >> P0420 Catalyst System Efficiency Below Threshold Bank 1 >> Possible Causes

Possible Causes

WARNING: This page is about a different car, the 2025 Jeep Grand Cherokee. However, it is still accessible from the selected car via links, so may be relevant.
Possible Causes
EXHAUST LEAK
ENGINE MECHANICAL CONDITION
AGING OR FOULED UPSTREAM O2 SENSOR
CATALYTIC CONVERTER

Always perform the PRE-DIAGNOSTIC TROUBLESHOOTING PROCEDURE before proceeding. Refer to:  2.0L - PRE-DIAGNOSTIC TROUBLESHOOTING PROCEDURE  .