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Old 12-19-2011, 11:06 PM   #1
nj06wrx
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Default How long after reset before ECU codes validate

My 06 wrx occasionally throws a 2443 error code. What I normally do is clear it and ignore it. It's the stupid cold start solenoid error that lots and lots of people get and it's pretty unimportant and even when it works it only controls emissions for about 1 minute after starting. Dumb design by Subaru and they won't admit it's a defect. Anyway....

Today I had to go and get the wrx inspected. I checked for pending codes and sure enough there was a 2443 code pending (it takes two to bring on the "check engine" light), so I cleared it.

After driving 10 miles to the inspection ststion they plugged me into their machine they got "not available" codes for a number of readings, which I understand is what they see when a battery has been disconnected and the ECU reset. I assume clearing any pending trouble codes does the same thing and it takes some time before the reset ECU figures out what numbers it should be reporting.

Does anyone know how long it takes for the ECU to come back online and provide readings for various emissions related parameters? I know it's not instant since it has to collect a certain amount of data before it outputs a valid code.

The guy at the inspection station said to just drive it around for a while then bring it back, but does anyone have a better estimate of how long it takes? 10 miles, 50 miles, 100 miles, 200 miles?
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Old 12-20-2011, 01:48 AM   #2
nydubber
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Usually around 40 is what we did when I worked at a dealership
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Old 12-20-2011, 03:40 AM   #3
alt14
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I have after market headers that have a cat in them that set off P0420 , I just disconnected the batter for about ten minutes then drove around for fifty miles or so then plugged in a diagnostics tool and It didn't know any code ever went off, not sure if that's the answer to home long your looking for but I hope it helps
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Old 12-20-2011, 08:01 AM   #4
Mulder
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What you are referring to are the "readiness monitors" which have to run through a specific driving cycle before being fully set. A reset or code clearing operation, or battery disconnect, will clear the monitors and force them to begin their cycle again. This is why you will fail an OBDII inspection right after pulling the battery or clearing codes.
The required cycle to set each of the monitors is different (i.e. sustained highway, stop and go etc) so they won't all set at the same time. Some may set almost immediately and others may take longer. The inspection regulations usually allow for the car to pass even if one or two of the monitors are not set, but unless you have checked the car with a scanner before going to the inspection station you won't know ahead of time if it's going to pass.
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Old 12-20-2011, 09:53 AM   #5
Uncle Scotty
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if you google 'obdII drive cycle'.....there are several that come up......and there IS one in one of the subaru manuals that tells you exactly how you need to drive the car to satisfy all the 'readiness' monitors....it is a bit complicated....but easily doable in an hour or so if you plan it out


ALSO......you can 'force readiness' with some engine management/tactrix
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Old 12-20-2011, 11:08 AM   #6
motohippy
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Some of them are really quite specific, even down to how much fuel you have in the tank. . .
I'm also not sure how the hell you're supposed to do one in particular (the evap system) without a closed course, dyno, or living in the absolute middle of nowhere. . .
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Old 12-20-2011, 03:38 PM   #7
nj06wrx
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Thanks! The term "OBDII Drive Cycle" was what I needed to do a search. Just for future reference, here is one such cycle I found (though not Subrau specific).

Quote:
Cold Start. In order to be classified as a cold start the engine coolant temperature must be below 50C (122F) and within 6C (11F) 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.

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.

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.

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.

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.

Accelerate. Accelerate at 3/4 throttle until 88-96 km/hr (55-60mph). This will perform the same diagnostics as in step 3.

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.

Decelerate. This will perform the same diagnostics as in step 5. Again, don't press the clutch or brakes or shift gears.
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