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

2 thoughts on “OBD II Monitor Readiness – Drive Cycle GM”

  1. 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

    1. 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.

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