It sounds like your Toyota 4Runner has reset its Emission Monitors. The Emission Monitors need to be made READY or COMPLETE in order to pass the smog inspection. Making the monitors READY requires completing a drive cycle specific to your Toyota 4Runner. Having simply driven your 4Runner, for any number of miles, may not complete the monitors if the specific drive cycle below is not followed.
We must warn you, the Toyota 4Runner drive cycle is not simply and requires may start and stops, as well as driving at both highway and city street speed limits. If you feel you might be unable to complete the drive cycle yourself, please seek assistance from a Toyota Repair Center or smog check repair station.
Toyota 4Runner Drive Cycle
A. Ensure to begin with your 4Runner having 1/4 to 3/4 tank full of gas, and after it has been sitting overnight. The engine must be cold before you begin the drive cycle. Also make sure the check engine light or MIL is not illuminated. If the check engine light is on, do not perform the drive cycle. Visit a smog check repair station for diagnosis. The check engine light must be off in order for the drive cycle to initiate.
B. Release the pressure in the fuel tank by removing and then reinstalling the gas cap. Start your 4Runner's engine and let it idle until it reaches normal operating temperature. Coolant temperature should reach 167F or above. If the temp gauge is near the center, you may continue on with performing the drive cycle.
C. Increase idle to 3000 rpm for 10 seconds. Allow the engine to return to idle, then turn on the A/C. Let the engine idle with the A/C on for 30 minutes.
D. Turn off the A/C and begin driving. Drive your 4Runner at 40 to 55 mph for 3 minutes, then decrease your speed and drive for 16 minutes, fluctuating your speed between 35 and 45 mph. It is very important that you accelerate and decelerate smoothly between 35 and 45 mph, during the 16 minutes.
E. Stop your vehicle and allow the engine to idle for 2 minutes or more. Begin driving once again. Drive your Toyota 4 Runner between 40 and 70 mph for at least 3 minutes. Be sure to maintain engine speeds between 900 and 3,200 rpm. Stop the vehicle and allow the engine to idle for 10 seconds or more. Begin driving again at 25 mph for one (1) minute. Be sure to maintain engine speed above 900 rpm. Stop the vehicle and allow the engine to idle for 10 seconds or more. Perform steps "E" ten times. This portion of the drive cycle is not easy to perform on public roadways. If you feel you are unable to perform this drive cycle safely please seek repair assistance from a Toyota certified or smog check repair certified center.
F. Drive cycle complete. If the above Toyota 4Runner Drive Cycle did not make all the emission monitors READY/COMPLETE, including the EVAP, CATALYST, O2 SENSOR, and O2 HEATER, perform drive cycle steps A through E again.
