Hello, My 2002 Jeep Liberty failed its smog check this morning because the OBD II diagnostics test states that the evaporative system and oxygen sensor heater are "not ready". The other monitors tested were fine. The smog tech believes the problem was caused by my battery being briefly disconnected a few days ago. He suggested I call Jeep and ask what the "reset driving pattern" is. Jeep was unhelpful. I've driven the car 120 miles since the battery disconnection and these sensors are still not ready. Any suggestions to get them reset would be greatly appreciated. John Fox

If you haven't already done so I recommend that you take your Jeep to an auto parts store and ask them to use a scan tool to check for diagnostic trouble codes, most stores will do this for free. If there are codes returned this information can point you in the right direction.

Do you know if the "smog tech" tried removing the fuel cap and repeating the test? This may sound silly but vehicles with a Fuel Tank Pressure Sensor sometimes show a fuel pressure fault that can be resolved by removing the cap to relieve pressure. The Fuel Tank Pressure (FTP) sensor is part of the evaporative emissions system. The engine control system monitors gasoline vapor pressures in the fuel tank to determine fuel tank sealing. The FTP sensor can be used in conjunction with an EVAP vent valve and an EVAP canister purge valve. It is possible that if the PCM detects a FTP fault that it may not activate the O2 Sensor heater.

I assume that during the smog test they check for vacuum leaks, but one could have been missed. A vacuum leak in the EVAP system could cause this kind of fault. The duty cycle EVAP canister purge solenoid (DCP) is in the engine compartment attached to a bracket between the battery and power distribution center (PDC). The EVAP system test port is near the solenoid.

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