OBD II Monitor Readiness – Drive Cycle GM

The following is the recommended driving cycle for General Motors.

A complete driving cycle should perform diagnostics on all systems. A complete driving cycle can be done in under fifteen minutes.

To perform an OBDII Driving cycle do the following:

  1. Cold Start. In order to be classified as a cold start the engine coolant temperature must be below 50°C (122°F) and within 6°C (11°F) of the ambient air temperature at startup. Do not leave the key on prior to the cold start or the heated oxygen sensor diagnostic may not run.
  2. Idle. The engine must be run for two and a half minutes with the air conditioner on and rear defroster on. The more electrical load you can apply the better. This will test the O2 heater, Passive Air, Purge “No Flow”, Misfire and if closed loop is achieved, Fuel Trim.
  3. Accelerate. Turn off the air conditioner and all the other loads and apply half throttle until 88km/hr (55mph) is reached. During this time the Misfire, Fuel Trim, and Purge Flow diagnostics will be performed.
  4. Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for 3 minutes. During this time the O2 response, air Intrusive, EGR, Purge, Misfire, and Fuel Trim diagnostics will be performed.
  5. Decelerate. Let off the accelerator pedal. Do not shift, touch the brake or clutch. It is important to let the vehicle coast along gradually slowing down to 32km/hr (20 mph). During this time the EGR, Purge and Fuel Trim diagnostics will be performed.
  6. Accelerate. Accelerate at 3/4 throttle until 88-96 km/hr (55-60mph). This will perform the same diagnostics as in step 3.
  7. Hold Steady Speed. Hold a steady speed of 88km/hr (55mph) for five minutes. During this time, in addition to the diagnostics performed in step 4, the catalyst monitor diagnostics will be performed. If the catalyst is marginal or the battery has been disconnected, it may take 5 complete driving cycles to determine the state of the catalyst.
  8. Decelerate. This will perform the same diagnostics as in step 5. Again, don’t press the clutch or brakes or shift gears.

Reprinted on OBDII web site courtesy of General Motors © GM

21 Replies to “OBD II Monitor Readiness – Drive Cycle GM”

  1. Seth

    Can I do the steps separate without having to do the full drive Cycle? Only the Cat and Evap are not ready and I live in the mountains. Also are other steps necessary for the evap and cat tests to run? Been going through hell trying to find a good straight flat road with no traffic and get the cold start while waiting 8 friggin’ hours each time.
    Thank you

    • Julius

      The Bureau of Automotive Repair recognizes that competing the EVAP monitor can be difficult, so your 2003 Silverado will pass the OBD II portion of the smog inspection with an incomplete EVAP monitor if the “Check Engine” (MIL, Service Engine…, etc) is not commanded on, and all other monitors are complete.

      That said, yes, you can complete the steps separately as long as all other pre-requisites for completing the monitor have been met. For example, on a 2003 Chevy C1500 2WD truck with a 4.8L V8 – VIN V), the following conditions would have to be met before attempting to complete the catalyst monitor:

        – The barometric pressure more than 74 kPA
        – Engine coolant temperature 160-248F
        – Intake air temperature 5-167F
        – Engine in closed loop fuel control
        – engine has run for 6-8 minutes off idle in order to initiate test
        – battery voltage 11-18 volts

        Once criteria has been met:

        – Turn off all accessories, including the A/C and the blower fan.
        – Start the engine, and allow the engine to idle
        – Accelerate at part throttle to 55mph and maintain speed for 5 minutes
        – Decelerate to 0 mph
        – Idle for two minutes with the brake depressed, transmission in drive (Or on a manual transmission, in Neutral with the clutch pedal depressed

      Again, meeting all the above criteria can be a challenge. Depending on your engine size, a different procedure may apply.

  2. Jim Musick

    I also live in the mountains but the only road to try to do the cold start is a major why so the coasting down to 20 mph is Almost impossible. any suggesting its a Chevy silverado 2005 5.3 vortex 4×4

    • dewok Post author

      Hi Jim,

      You may need to drive in a different location. Beyond driving conditions, I have read that some vehicles have difficulty settings monitors at higher elevations.

    • Staci

      That’s my exact dilemma.. 2004 Chev Tahoe OBD2 is not ready due to recent mechanical work that cleared the computer.. I can/did all the steps this weekend but I can only drive 55mph on the HWY and coasting down to 20 MPH is impossible not to mention a death trap on these LA freeways..

    • dewok Post author

      Hi Ediwn,

      It depends on the particular vehicle. Some vehicles can set the oxygen sensor heater monitor simply by warming up in park from a cold start.

      Just Smogs

  3. john

    When doing GM s drive cycle I noiticed the cat didn’t complete until you really gun it up to 55 you know punch it… I guess it checks flow making sure it has no backpressure, as to, Its not plugged.. so during the test punch it up to 55

  4. Robert

    I got the same thing ..cat “not ready”and “evap” not ready on my 03 GMC sierra. I’ve put$140.00 in fuel so far and drove it like there saying with atleast 5 drive cycles and still got nothing. I’m within 150 dollars of my registration costing me 2,000 dollars. This has to be one of the biggest jokes I’ve come across. I’ve got no check engine light on after 350 miles so what now???? I just keep paying until everything is replaced and then have my truck junked because of this

  5. Chris Oliphant

    I have a 2010 GMC box truck (cutaway) that will not clear the EVAP module in the OBD11. No codes, no pending codes everything else has cleared and I’ve followed all the recommended procedures to clear the EVAP module. Truck has been driven over 600 miles. Of course the rules were changed on July 1st where all modules had to clear before the truck would pass smog. Prior to that if the EVAP had not cleared we were good to go.

    Any thoughts regarding this. Any help would be appreciated.

    • dewok Post author

      Hi Chris,

      The only thing that has changes in regards to the California smog check is that California now fails vehicles that have a permanent DTC stored. As of right now (August 2019), your vehicle will still pass a smog check with the EVAP monitor incomplete (As long as all other monitors are complete and there are no stored permanent DTC(s).

      The only way to clear a PDTC is to fix the underlying problem with the vehicle that originally caused the PDTC and its corresponding DTC to set, and then allow the vehicle sufficient drive time to re-run the monitor that identified the problem in the first place. When the monitor runs without identifying a problem, the PDTC will clear itself.

      So if there is a permanent DTC, you just have to keep driving the vehicle until it clears itself.

      • Chris Oliphant

        Ah, there’s the rub. As of July 1st ALL PDTC’s have to clear, including the EVAP module, before it will pass smog.

        After much trial and error (ambient temperature appears to plays a major role here) the EVAP finally cleared. It took me 720 miles but I believe I can shorten that if I do it better.

        It wouldn’t matter if it was my vehicle but I sell (we’re a licensed dealer) the off rental box trucks for Uhaul here in Fremont and of course I need a smog it before I can sell it within CA.

        I have one more coming up where the OBD codes have been erased after repairs. I just hope from what learnt doing this one I can save some time and gas getting everything to set.

        Thanks for your help


  6. Jack

    I have a 2005 Chev Tahoe 5.3 —I have no stored codes—-no lights—but cat monitor will not ready for test. Drive over 500mi—high octane gas—tried to follow procedures for readying monitor but no luck so far. Any help appreciated.

    • dewok Post author

      Hi Jack,

      Chevys usually set the readiness monitors if you follow the drive cycle procedure. We have found that some GMs with thermostat/cooling system issues are unable to warm up properly and in turn will not complete the catalyst monitor. Other times the catalytic converter(s) are not “efficient” enough to set the monitor to ready but at the same time not bad enough to set a trouble code.

  7. OSCAR. C.


    • dewok Post author

      Hi Oscar,

      Most vehicles require between 1/4 and 3/4 of fuel for the EVAP monitor to complete. I don’t believe that the broken A/C system will prevent the readiness monitors from completing on your vehicle.


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