2000 Town Car - 3 codes (P0307 - I believe misfire on #7) but P0430 & P0442 I don't know

P0430 - Catalyst System Efficiency Below Threshold (Bank 2) Indicates Bank 2 catalyst system efficiency is below the acceptable threshold.

• Use of leaded fuel
• Damaged HO2S
• Malfunctioning ECT
• High fuel pressure
• Damaged exhaust manifold
• Damaged catalytic converter
• Oil contamination
• Cylinder misfiring
• Downstream HO2S wires improperly connected
• Damaged exhaust system pipe
• Damaged muffler/tailpipe assembly
• Retarded spark timing

Compare HO2S upstream & downstream switch rate. Under normal closed loop fuel conditions, high efficiency catalysts have oxygen storage which makes the switching frequency of the downstream HO2S quite slow compared to the upstream HO2S. As catalyst efficiency deteriorates, its ability to store oxygen declines and the downstream HO2S signal begins to switch more rapidly approaching the switching rate of the upstream HO2S. Once beyond an acceptable limit the DTC is set. Catalytic converter bad !


P0442 - EVAP Control System Leak Detected (Small Leak) The PCM monitors the complete EVAP control system for presence of a small fuel vapor leak. The system failure occurs when a fuel vapor leak from an opening as small as 1.016 mm (0.04 inch) is detected by the EVAP running loss monitor test.

• After-market EVAP hardware (such as fuel filler cap) non-conforming to required specifications
• Small holes or cuts in fuel vapor hoses/tubes
• Canister vent solenoid stays partially open on closed command
• Damaged, cross-threaded or loosely installed fuel filler cap
• Loose fuel vapor hose/tube connections to EVAP system components
• EVAP system component seals leaking (EVAP canister purge valve, fuel tank pressure sensor, canister vent solenoid, fuel vapor control valve tube assembly or fuel vapor vent valve assembly)

EVAP Leaks P0442 and P0455