Having replaced your Mitsubishi Montero's battery caused the OBDII monitors to erase, requiring a drive cycle be completed in order to make the monitors READY or COMPLETE again. Follow the Mitsubishi Montero drive cycle below. The required monitors should become ready to pass the smog inspection simply by driving your Montero for 200-300 miles and over the course of a few days. We notice you mention having been to the smog station 4 times already with unsuccessful results. We'd like to note, due to individual driving habits/patterns, sometimes the drive cycle parameters are not met with ordinary driving, and following the Mitsubishi Montero drive cycle is necessary.
Specific to the EGR monitor not completing... It has been reported that the EGR monitor may not be activated because of a misadjusted throttle plate (butterfly). Ensure your Montero's throttle idle screw is adjusted correctly and that the butterfly within the throttle body is to specification when the gas pedal has been released. If any adjustment is made to the idle screw, you may need to also adjust the throttle position sensor. Bringing the throttle adjustment to zero (0) has been known to allow the EGR monitor to complete.
Take extra caution when performing drive cycles on public roadways, obeying all traffic laws. You may also seek repair assistance from a Mitsubishi dealership. They will be able to complete the drive cycle using manufacture specific scan tools. If after performing the drive cycle twice, your Montero is still unable to pass the smog check because its monitors (or monitor) is incomplete, please seek assistance from a smog check repair center or Nissan dealership.
2001 Mitsubishi Montero Drive Cycle
A. Begin from Cold Start, and ignition in OFF position for at least 1 hour. Ensure your Mitsubishi's fuel tank is between 1/4 and 3/4 full. Engine coolant temperature must be below 122°F and within 11°F of the ambient air temperature.
B. Idle. Run engine (do not drive) for 2 1/2 minutes with the accessories off. Put the vehicle is Drive (D) while pressing the brake pedal, and hold for 15 seconds. Put the vehicle in Park and turn the ignition to OFF position. Repeat this step once. The ECU will run the Oxygen Sensor Heater self-test and EVAP Purge "No Flow" test.
C. Start the vehicle and turn all accessories off. Begin to drive. Apply half throttle until 55 mph is reached. The ECU will now begin the EVAP Purge Flow test.
D. Hold your speed steady at 55 mph for five (5) minutes. During this time the Oxygen Sensor O2 response, Air Intrusive (AIS System), EGR Flow, Purge Valve, Misfire Detection, and Fuel Trim diagnostics will be performed.
E. During this step slowly let off the accelerator pedal. Do not brake or shift in order to slow down. It is important to let your Montero coast along gradually slowing down to 10 mph. The ECU will once again self-test the EGR System, EVAP Purge System and Long Term Fuel Trims.
F. Accelerate again at 3/4 throttle until 55-60 mph is reached. This will perform the same self tests as during the first acceleration step.
G. Hold steady speed once again. This time at 55 mph for two (2) minutes. During this time the ECU will perform the catalyst monitor diagnostics.
H. Decelerate. This will perform the same diagnostics as in the first deceleration step. Remember not to press the brake or shift gears.
This ends the Mitsubishi Montero Drive Cycle. Performing the drive cycle at least twice, or using your scan tool check to see if one drive cycle set the EVAP monitor to "Ready".