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Failed Smog Test

I Need the Drive Cycle for a BMW Z4

Just bought a 2004 BMW Z4. 123,000 miles. It's a weekend car. The catalyst monitor keeps failing smog check. I tried to do "drive cycle procedure" but still failed. Any suggestions?


Your BMW Z4 will need to have all the emission monitors "ready" or "complete" before it can pass the smog test. 2002 & newer BMW Z4'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.

How to Perform a BMW Z4 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. The secondary air injection and EVAP leak detection tests are being conducted now.

B. Begin driving. Accelerate to 20-30 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. Accelerate to 40-60 MPH and maintain steady speed for 15 minutes. The catalyst monitor is being run now.

D Decelerate to a complete stop and idle while the engine is in gear for 5 minutes. The ECU is testing the system for EVAP leaks.

E. 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 Z-Series 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.

posted by SmogTips Support

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