After changing sensors that were bad on a Toyota 4Runner an emmissions technician stated that the vehicle needed to be driven "for awhile" before the "drive cycle" would reset the ECU to the new sensors and properly measure out fuel and what not for the motor to consume.

What is the length of time required for the 'drive cycle reset' to occur?

1 Answer 1


This is a bit complicated, but I found the information for you on this pdf. I am pulling the graphs out of it so you can see what you need to do. Rather than retype everything, I'm cutting/pasting some of the precursor directions here:

There are some prerequisites you should know. First, you need a scan tool to tell you when any of the drive cycles are complete and the On–Board Diagnostic (OBDII) system is designed to monitor the performance of emission–related components and report any detected abnormalities in the form of Diagnostic Trouble Codes (DTCs). Since the various components need to be monitored during different driving conditions, the OBDII system is designed to run separate monitoring programs called Readiness Monitors. Many state Inspection and Maintenance (I/M) programs require that vehicles complete their Readiness Monitors prior to beginning an emissions test.

The current status of the Readiness Monitors can be seen by using the Toyota Diagnostic Tester with version 9.0 software (or newer), or a generic OBDII Scantool.

To view the Readiness Monitor status using the Toyota Diagnostic Tester, select “Monitor Status” from the Enhanced OBDII Menu.

A status of “complete” indicates that the necessary conditions have been met to run the performance tests for the related Readiness Monitor.

The Readiness Monitor will be reset to “incomplete” if:

  • List item ECU has lost power (battery or fuse).
  • DTCs have been cleared.
  • The conditions for running the Readiness Monitor have not been met.

In the event that any Readiness Monitor shows “incomplete,” follow the appropriate Readiness Monitor Drive Pattern to change the readiness status to “complete.”

With some further warnings of:


  • These drive patterns represent the fastest method to satisfy all necessary conditions which allow the specific Readiness Monitor to complete.
  • In the event that the drive pattern must be interrupted (possibly due to traffic conditions or other factors) the drive pattern can be resumed and, in most cases, the Readiness Monitor will still set to “complete.”
  • To ensure rapid completion of Readiness Monitors, avoid sudden changes in vehicle load and speed (driving up and down hills and/or sudden acceleration).

NOTE: Please don't let this intimidate you. There seems like a lot of prerequisites and such, but really, most, if not all, are pretty straight forward. If you look for patterns in what it's asking you to do, you can probably come up with a plan to have all of them complete in one trip.

This first grid shows which Drive Cycles to actually follow:

enter image description here

This shows you need to worry about Drive Cycles 4, 6, 10, & 11. (Note: Mind you, some of these may have already been validated in the amount of time you've had your vehicle back from the mechanic. Pay attention to the Drive Cycles which are left. If it's already validated, don't worry about doing the Drive Cycle.)

Here is the graph for Drive Cycle 4:

enter image description here

Here is the graph for Drive Cycle 6:

enter image description here enter image description here

Here is the graph for Drive Cycle 10:

enter image description here

Here is the graph for Drive Cycle 11:

enter image description here

  • @DucatiKiller - YW! Anytime bro. May 1, 2015 at 20:13
  • Great answer. I guess it is not possible to add a tl;dr answer to this question.
    – rana
    Oct 9, 2015 at 17:53
  • @rana - Yah, it really could use a Reader's Digest Condensed version, eh? Thanks for the compliment. Oct 9, 2015 at 18:00
  • Thank you very much for your help. My Autel Maxisys scanner do not have this fonction. Today it took about 15 mins running in urban streeet (10 Km or so) to get EECM in close loop after a long period been disconnected.
    – Jean
    Apr 30 at 1:55

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