P0420 on Jeep
Catalyst System Efficiency Below Threshold (Bank 1)
P0420 on Jeep vehicles indicates catalyst system efficiency below threshold (bank 1). Au7o has documented this code across 6 Jeep models — most commonly on Cherokee, Comanche, Compass. P0420 means the engine computer determined the catalytic converter on Bank 1 isn't cleaning the exhaust as efficiently as it should. The computer compares the upstream and downstream oxygen sensors; a healthy converter stores and releases oxygen, so the downstream sensor should read fairly steady, while a worn one lets its readings mirror the upstream sensor. When that efficiency falls below a set threshold, this code is set. While it most often points to a worn-out catalytic converter, it can also be triggered by upstream problems like a faulty oxygen sensor or an exhaust leak, so the converter isn't always the actual fault. Typical repair costs on Jeep range from $50 to $8,500, depending on the specific model and root cause.
Common Causes of P0420
- •Worn-out or failing catalytic converter (Bank 1)
- •Faulty or aged downstream (or upstream) oxygen sensor
- •Exhaust leak before or near the oxygen sensors
- •Engine running rich or lean (fuel trim issues)
- •Misfires or oil/coolant contaminating the converter
- •Damaged or aftermarket low-quality catalytic converter
- •Faulty oxygen sensor wiring or connectors
- •Software/calibration needing update (on some vehicles)
P0420 on Jeep by Model
Jeep Cherokee(1 issue)
- Excessive Oil Consumption (2.4L Tigershark)2014-2019
The 2.4L Tigershark MultiAir engine suffers from defective piston rings allowing oil to burn in combustion chamber. Owners report consuming 1 quart per 1,000 miles. Engine can stall when oil falls below 3.5 quarts without warning light.
Jeep Comanche(1 issue)
- 4.0L Inline-6 Exhaust Manifold Cracking1990-1992
The cast iron exhaust manifold on the 4.0L AMC/Jeep inline-6 engine is prone to cracking from thermal stress cycling. The manifold design does not accommodate thermal expansion well, and cracks develop between the exhaust ports, typically between cylinders 3-4 or 5-6. Cracked manifolds cause exhaust leaks that are loudest on cold startup and may quiet down as the manifold expands when hot. The exhaust leak can cause a ticking or hissing sound that is often mistaken for a lifter or valve issue. Broken exhaust manifold bolts are extremely common and can complicate the repair.
Jeep Compass(1 issue)
- 2.4L Tigershark Oil Pump Failure / Engine Stalling2017-2022
The 2.4L Tigershark engine may experience oil pump failure where insufficient oil pressure causes the engine to stall while driving. NHTSA Recall 17V-670 (October 2017) addressed oil pumps that would not deliver adequate pressure. The engine uses hydraulic valve actuators that rely on oil pressure, so low oil starves the valvetrain and causes sudden stalling. Excessive oil consumption between changes exacerbates the problem.
Jeep Grand Cherokee(1 issue)
- Exhaust Manifold Bolt Failure and Manifold Leak on 4.7L V81999-2009
The 4.7L V8 used in Grand Cherokee models is widely reported to develop broken exhaust manifold bolts or warped manifold sealing surfaces, especially after repeated heat cycles. Owners typically notice a ticking noise on cold start that may quiet as the engine warms, sometimes mistaken for valvetrain noise. Left unrepaired, the leak can worsen and may contribute to exhaust odor or failed emissions inspection.
Jeep Renegade(1 issue)
- 2.4L Tigershark Excessive Oil Consumption2015-2020
The 2.4L Tigershark MultiAir engine consumes oil at an abnormal rate, sometimes exceeding 1 quart per 1,000-2,000 miles. The MultiAir valve actuation system uses engine oil to operate the intake valves, and the system can develop internal leaks. Worn piston rings and valve seals also contribute. If oil level drops too low, the engine may stall or suffer catastrophic damage.
Jeep Wrangler(2 issues)
- Pentastar V6 Oil Consumption2012-2018
The 3.6L Pentastar V6 can consume oil at a rate higher than expected, sometimes requiring oil top-ups between changes. This is often related to piston ring design or valve guide seals. Chrysler considers up to 1 quart per 2,000 miles as within normal range.
- Catalytic Converter Failure and Pre-Cat Efficiency Codes on 4.0L2000-2006
TJ Wranglers with the 4.0L frequently develop catalytic converter deterioration, especially on higher-mileage vehicles and 2000-2006 emissions configurations using multiple converters/pre-cats. Owners commonly report a check-engine light with catalyst-efficiency codes, sulfur smell, rattling substrate, or loss of power if the converter begins to clog. This issue is well documented in owner complaints, repair databases, and Jeep service information.
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View P0420 across all makes →Frequently Asked Questions
What does P0420 mean on Jeep?▼
P0420 stands for "Catalyst System Efficiency Below Threshold (Bank 1)." P0420 means the engine computer determined the catalytic converter on Bank 1 isn't cleaning the exhaust as efficiently as it should. The computer compares the upstream and downstream oxygen sensors; a healthy converter stores and releases oxygen, so the downstream sensor should read fairly steady, while a worn one lets its readings mirror the upstream sensor. When that efficiency falls below a set threshold, this code is set. While it most often points to a worn-out catalytic converter, it can also be triggered by upstream problems like a faulty oxygen sensor or an exhaust leak, so the converter isn't always the actual fault. On Jeep specifically, this code is documented across 6 models.
What causes P0420 on Jeep vehicles?▼
Common causes on Jeep: Worn-out or failing catalytic converter (Bank 1), Faulty or aged downstream (or upstream) oxygen sensor, Exhaust leak before or near the oxygen sensors, Engine running rich or lean (fuel trim issues), Misfires or oil/coolant contaminating the converter. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0420 on a Jeep?▼
Repair costs on Jeep range from $50 to $8,500, depending on the specific model and root cause.
Which Jeep models have P0420 documented?▼
Au7o has documented P0420 on 6 Jeep models: Cherokee, Comanche, Compass, Grand Cherokee, Renegade, Wrangler.