Your BMW 325i will need to have all the emission monitors "ready" or "complete" before it can pass the smog test. 2001 & newer BMW 325i's must have all the monitors ready, except the EVAP. The EVAP monitor is the only one that is allowed to remain incomplete and your vehicle still pass the smog test. NOTE: You'll notice below, the secondary AIR monitor runs when the engine is cold, and best when the BMW has been sitting overnight. We recommend ensuring the monitor's parameters (requirement for engine to be cold) are being met. If the AIR injection pump is not running in the mornings when the engine is first started and the weather is cold, the AIR monitor will not complete.
You will need to perform a drive cycle on your BMW 325i if you have replaced the battery, disconnected the battery, or cleared the codes after a repair. The driving cycle performs a diagnostic test on all the emission systems and enures your vehicle is not polluting.
Usually driving 200-300 miles over the course of a few days and in both city and highway traffic conditions is enough to get the drive cycle complete. Due to individual vehicle owner driving patterns however, sometimes the criteria required to get a particular monitor to initiate and/or become ready is not met. In such instances, it is required that a specific drive cycle pattern which is designed for the BMW, be followed.
How to Perform a BMW 325i Drive Cycle
Begin by: (Make sure you have between 1/4 and 3/4 fuel in the gas tank. The EVAP test will not run while your BMW has a full tank of gas or the gas tank is near empty. Ensure there are no pending or active trouble codes and that the check engine light is not on. Start the drive cycle from a cold start; preferably on a cold morning.
A. Start engine and idle for approximately 2 minutes and 10 seconds. This tests the Secondary Air Injection, O2 Heater, EVAP/Purge No Flow, and Misfire systems. If your BMW achieves closed loop, the fuel trim will also be tested as well.
B. Begin driving. Accelerate to 55 MPH and maintain steady speed for 3 minutes and 15 seconds. During this drive segment the ECU is checking closed-loop operation and oxygen sensor response time.
C Release the accelerator pedal and coast down to 20 MPH without shifting or touching the brake or clutch (if equipped). Continue to STEP D once your vehicle speed reaches 20 MPH.
D. Accelerate to 40-60 MPH and maintain steady speed for 15 minutes. The catalyst monitor is being run now.
E. Decelerate to a complete stop and idle while the transmission is in PARK or neutral for 5 minutes. The ECU is testing the system for EVAP leaks.
F. End of Drive Cycle
If readiness status of all monitors do not switch to “ready,” ensure preconditions are met, and complete a new drive cycle after the engine has cooled overnight. The BMW 325 drive cycle (drive trace) requires driving both highway and city speeds. If you feel you might be unable to complete the drive cycle safely, please seek assistance from a BMW repair center or smog check repair station. Conduct this drive cycle at your own risk.
