1996 Jaguar XJ6 emissions

1996 JAGUAR XJ6
108,913 MILES • 6 CYL • 2WD • AUTOMATIC
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DENNIS MAHLING
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I get a check engine light code PO420 which reads Catalyst System efficiency below threshold (Bank 1) A couple of times the engine ran rough when warm. Could this be a bad oxygen sensor or a bad catalytic converter?

My car also shows a symbol on the dash instruments when I step on the brake pedal. Does this mean the booster is low or bake pads are worn down?
Aug 4, 2008 at 6:32 PM
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.
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