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.
Yes, I am experiencing this now with a 2000 Camry V6. The O2 sensors were replaced in 2012 and I suspect they used inferior parts, because every now and then the trouble light comes on (maybe once in a few years).
I have been using my OBD II device along with an app called Torque to reset the error when it happens (like, twice since 2012), and it typically does not come back for a year or more. And I passed my last CA smog inspection.
But this year the car failed the smog test, not because of an active DTC, and not because of the manual clearing of the codes, which last happened a couple of years ago, but because the car had not been run enough since the last DTC to validate the O2 monitor.
I looked in the manual, and to reset that O2 DTC you need to idle for 2 minutes, and then drive 50 seconds+ above 25mpg followed by 40 seconds idling, repeating that sequence ten times.
I drive 99 percent short local trips, and only 2,000 miles per year, so it probably takes a while for me to fulfill that pattern. This means that if there is a DTC code detected occasionally, the monitor may get stuck without being reset for a fairly long time. And yet, the trouble light typically does not come on, because you need two trips in a row with the DTC detected before that light will illuminate.
So the car is in a kind of limbo, in which at times it may not have an active DTC but may also not have been driven enough to be reset since the last DTC that occurred. And you can be unaware of this until you get to your friendly Smog check station.
I should have used my OBD II device to view the status of the monitors before taking the car in. At this point, I’ll just drive the prescribed sequence, check OBD for the reset having occurred, and, if it has, drive it back for a re-test. If it has not occurred, then I’ll have to take it to the shop for a new sensor, and get a good one this time.