Run cycles

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Specifically, with regards to OBD2.

- What constitutes a "run cycle?" (Is it not 1. Turn key and start car, 2. possible engage a gear, 3. Drive, or turn car off?)
- How many does it take to get an ECU ready to be scanned by Inspection?

Took the Expo to NJ MVS Inspection in Secaucus the other day. They told me the ECU "was not ready to be scanned."
 
It varies a bit by manufacturer but usually it is something like:

"when the Oxygen Sensor Monitor and the Catalyst Monitor have been completed in the same drive cycle."

It's not just start car and shut it off.
 
I've seen this issue come up before on various car forums. It may vary by vehicle, but if you start from a cold engine and drive until warmed up a couple of times and put about 20 miles on the odometer you should be good. Obviously you don't want to clear codes or disconnect the battery, which resets the clock.
 
If you haven't monkeyed with it recently, it's possible it has a bad thermostat and never gets up to temp to run the cycles.

But where your brake fluid is going, is more important.
 
Originally Posted By: ARCOgraphite
Trying to avoid a MIL lamp but still have the ECU ready for scan?

That's not possible, if your jurisdiction scans the computer for what are known as readiness monitors.

Readiness monitors are not set until their tests are run and passed. If the test fails or does not run, the monitor will report "not ready". The MIL may or may not illuminate at the same time, depending on the test.

Many jurisdictions allow at least one "not ready" monitor while still permitting a pass.

As for drive-cycles, they vary depending on manufacturer and the OBD-II test you're trying to force to run. Which one are you afraid of?
 
Originally Posted By: ARCOgraphite
Trying to avoid a MIL lamp but still have the ECU ready for scan? Or just malfunction prone?


... ?
 
Originally Posted By: Tegger
Originally Posted By: ARCOgraphite
Trying to avoid a MIL lamp but still have the ECU ready for scan?

That's not possible, if your jurisdiction scans the computer for what are known as readiness monitors.

Readiness monitors are not set until their tests are run and passed. If the test fails or does not run, the monitor will report "not ready". The MIL may or may not illuminate at the same time, depending on the test.

Many jurisdictions allow at least one "not ready" monitor while still permitting a pass.

As for drive-cycles, they vary depending on manufacturer and the OBD-II test you're trying to force to run. Which one are you afraid of?


I am not certain...

I think they want it to run a certain amount of time, as they want to be satisfied that I am not trying to "fool" the scan test. Not sure what isn't "ready" about it.
 
The OBDII setup was required to do various system checks. This was to make sure nothing had been tampered with. However, on OBDI one could clear the codes 5 seconds before going into the shop, and pass emissions--but with a car that had problems. Thus part of OBDII protocol are "readiness" flags. You can think of them getting checked off as the ECU finishes testing all systems. If a system were to fail, I'm not sure if sets readiness flag or not; but it'd set a code so it wouldn't matter.

As stated above, sometimes it takes several cycles to set the readiness flag. Evap may require sitting overnight, various other systems might be a few cold/hot cycles, who knows (unless if it's printed in the service manual).
 
Originally Posted By: MalfunctionProne
I think they want it to run a certain amount of time, as they want to be satisfied that I am not trying to "fool" the scan test.

That's not how it works. OBD-II cannot be "fooled" the way previous OBD systems could be. The monitors are either ready or they are not. OBD-II tests are run by the computer in the background while you drive. You are never even aware of it.

I think the period of engine-idle is used to check for exhaust leaks, etc. Stuff you wouldn't be able to tell unless the engine is running.


Originally Posted By: MalfunctionProne
Not sure what isn't "ready" about it.

Here's a partial screen-shot from a certain OBD-II diagnostics program. This screen-shot is from the program's built-in simulation, since I didn't have the laptop actually connected to any car at the time.
monitors.jpg


Note that three tests are green. The green means that the OBD-II computer has successfully run and complete the tests for that monitor, and the system passed the test. These monitors are therefore reported "Ready".

The two red monitors are problem areas. The OBD-II computer has determined that both tests either did not run, or ran and failed. Those monitors are therefore reported "Not Ready".

Note that the two Oxygen Sensor tests are not supported by the simulated car's computer. Which is weird since in real-life they would definitely be supported by any OBD-II vehicle.
 
Test stations here routinely instruct people to drive "a couple hundred miles" to set ready. That should do it, in most cases.

However, if you did not clear the codes or disconnect the battery prior to the test (or shortly before) it becomes a question of "why isn't it ready".

To Teggars excellent post I will only add that in my experience they often run in an order, so if for instance the O2 monitoring isn't complete, some of the others won't run.

If you google "drive cycle" for your particular make and model you will probably find a procedure to drive the car which should set readiness provided that you can follow it and there is nothing else wrong.
 
Originally Posted By: DuckRyder
Test stations here routinely instruct people to drive "a couple hundred miles" to set ready. That should do it, in most cases.

Yes, it certainly will. Within a couple hundred miles, most drivers will encounter all the driving conditions that are required for the OBD-II computer to run all its tests.

Manufacturers' drive-cycles are meant as a time-saving shortcut: they force the tests to run within the shortest time-frame possible. This is handy when you've just performed a repair and need to make certain the fix worked before returning the vehicle to the owner. It's also handy when a vehicle needs to pass emissions right away (such as when someone has left his emissions test until the day before his birthday...).

Originally Posted By: DuckRyder
However, if you did not clear the codes or disconnect the battery prior to the test (or shortly before) it becomes a question of "why isn't it ready".

Yes, but... Some models are known for having less-than-perfect OBD-II systems; these models can have monitors that never report "Ready" no matter what you do. And some owners drive so little and for such short intervals that some tests never run. For these reasons, many jurisdictions allow one (sometimes two) "Not Ready" monitor(s) while still qualifying the vehicle for a "Pass".
 
Originally Posted By: Tegger
Great! Did they give you a printout? And if so, are there any "Not Ready" monitors?


I was just about to ask, or say.. I recall there being a site where you could plug the VIN in, and get those numbers. But maybe only for cars that failed? Or is that wrong?

Does anyone know the site for NJ? I would put the VIN in!
 
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