The first thing neccessary to do is obtain an accurate diagnosis of your Toyota Highlander's emissions results; the actual results of tailpipe emissions. Is the catalytic converter actually defective? Or are the sensor(s) not working. Only a reputable smog check and repair certified smog check station will be able to tell. Using a 5 gas analyzer (or BAR 97 smog test machine) they should diagnose your Highlander's fuel feedback system to ensure all emission systems are functioning properly. Once they verify the emissions system if free from problems, they can then continue on to trying to get the Emission Monitors to pass, in this case, along with other monitors, the CAT monitor.
If in fact the catalytic converter is damaged, the emiission monitor for the catalyst will not set (become READY or COMPLETE). Replacing the catalytic converter will be required. Bottom line is before replacing anything it is very important to obtain an accurate diagnosis of your Toyota Highlander's emissions system.
For yout reference below you will find the Drive Trace for a Toyota Highlander, also known as a Toyota Highlander Drive Cycle. The following driving pattern is required in order for the engine contorl module to initiate a Drive Cycle; which will test all emission systems and report their status as READY (or COMPLETE), or INCOMPLETE... meaning either the drive pattern was not or has not yet been followed thoroughly, or a problem exists which is not allowing the computer to complete the drive cycle. NOTE: If you feel you might be unable to perform this drive cycle on public roadways safely please seek repair assistance from a Toyota certified or smog check repair certified center.
Toyota Highlander Drive Cycle
A. Ensure to begin with your Highlander 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 Highlander'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 Highlander 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 Highlander 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.
F. Drive cycle complete. If the above Toyota Highlander 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.
