Toyota Camry Failed Smog : Not Ready : No Check Engine Light

Our customer’s 1999 Toyota Camry CE 2.2L failed the biennial smog check inspection (category: OBD System Checks for being “Not Ready“). In most situations driving the vehicle for a week or two (streets & highway) will allow the vehicle to complete it’s self tests (readiness monitors) and become “Ready” so that it will pass the emission inspection.

Unfortunately, our customer drove almost 500 miles and still his Toyota was Not Ready for the following three monitors: Catalyst, Oxygen Sensor & Oxygen Sensor Heater.

He asked us to diagnose the problem. Although there was no check engine light illuminated, there as a pending diagnostic trouble code (DTC) stored in the vehicles computer: DTC P1155. P1155 is a manufacturer specific code relating to the Air/Fuel Ratio Sensor Heater Circuit.

Our technician diagnosed the air/fuel sensor and confirmed an open heater circuit. We replaced the a new Denso air/fuel sensor, cleared the fault code, and drove the vehicle.

In less than 20 miles of our drive cycle all three incomplete monitors (Catalyst, Oxygen Sensor & Oxygen Sensor Heater) became “Ready”. We re-tested the Camry and it passed.

Although in most “Not Ready” failed smog check situations, a vehicle can be driven to become “Ready” and pass a California smog inspection, repairs are sometimes necessary.

 

1996 to 2002 Toyota OBD II Catalyst Monitor Readiness Drive Patterns

The catalyst monitor on many Toyota vehicles can be difficult to complete.  That’s why it’s important to follow the Toyota recommended drive cycle after performing actions that are known to clear your Toyota’s computer memory.

Remember, all on-board diagnostic monitors are cleared when the battery is disconnected, or when the power train control module (PCM) is cleared with a scan tool.

CATALYST MONITOR DRIVE CYCLE INSTRUCTIONS

  1. Do not turn off the ignition switch during the test procedure.
  2. Allow the vehicle to run at idle until warmed up.
  3. Drive at a steady speed between 40 and 70 MPH for 10 minutes.  It’s a good idea to stay in the middle of this range, so 55 MPH is optimal.
  4. It may take several attempts and warm up cycles to complete the drive cycle.

toyota-drive-cycle-obd-readiness-monitor-smog-check

 

 

 

1996 to 2002 Toyota OBD II Monitor Readiness Drive Patterns