Replacing the battery or having simply disconnected the battery on your Hyundai Elantra caused the engine control unit (ECU) to reset and clear all the emission monitors; including the trouble code which was causing the check engine light to turn on.
Completing or making "Ready" the emission monitors requires driving your Elandra through a specific drive cycle. Emission monitors are internal self-tests which the ECU performs to ensure a vehicle is not polluting and is running efficiently. The entire process of self-testing various emission control systems is called a Drive Cycle.
It is recommend to simply drive a vehicle 200-300 miles and over the course of a few days in both city and highway traffic conditions in order to make the emission monitors "ready" or "complete".
Below you'll find a description of the Hyundai Elantra Drive Cycle. You should complete this drive cycle at least two consecutive times, allowing for a 5 minute break in-between with the ignition turned off. Also ensure your Hyundai Elantra's fuel tank is 1/4 to 3/4 full. An empty gas tank or full gas tank will not allow the EVAP monitor to run.
Take extra caution when performing the drive cycle on public roadways. If you feel you might be unable to perform the drive cycle safely, seek assistance from a smog check repair station or Hyundai service center.
How to Complete Hyundai Elantra Drive Cycle
STEP 1:
• Make sure check engine light is not on and that there are no stored trouble codes in the computer. Use a scan tool to check for OBD II trouble codes. Any faults founds need to be repaired first.
• Start the engine.
• Warm up the engine (15 minutes at idle).
• Turn OFF the A/C.
STEP 2: (Steady State Driving - This is the main section of the drive cycle)
• Drive your Hyundai Elantra for 10 minutes at a steady state where the engine speed is between 2,000
and 2,400 RPM in 5th gear on a manual transmission equipped
Hyundai and “D” position on an automatic, using very little throttle.
Note: If during this step your Hyundai falls out of the required engine RPM do not worry. Simply attempt to get back into the stead state drive mode when possible. The 10 minute count timer will re-continue when proper RPMs are met.
STEP 3: (Switch from Steady State Driving to an Idle State)
• Bring the vehicle to a stop at a location where the vehicle may idle.
• Place the transmission in neutral or park
• Allow the vehicle to idle for one minute.
• After one minute of idling, press the throttle quickly to take the engine off of idle for a brief second.
• Allow the vehicle to idle for one more minute.
STEP 4: (Engine Stop)
• The drive cycle is completed.
• Turn off the engine (key in the OFF position) and wait 30 seconds.
• After 30 seconds, restart the engine and complete the drive cycle steps 1 through 6 one ore time. As mentioned earlier, the drive cycle must be completed twice.
STEP 5: (Final)
• After the conclusion of the second drive cycle, turn the key to the ON
position. Check to see if the Readiness Monitors indicate READY.
If all other emissions systems are functioning properly, completing the drive cycle above twice should set or make ready (complete) your Hyundai Elantra's emission monitors. If the emission monitors are still not complete then check for any trouble codes and whether the check engine light is on or not. If faults are found make the appropriate repairs and conduct the drive cycle twice again. Take extreme caution when performing drive cycles on public roadways.
