VikingBlue

I disconnected the battery last night and reconnected this a.m., and as expected the check engine is not on anymore.

I've heard over the years that this won't 'fool' inspection centers as their readers will detect that the battery had been disconnected...but the sources for that info weren't any more knowledgeable than I.

Is that true ? if so, how long driving around before the recent disconnect is no longer readable by their monitors ?

oldcutlass

I don't know about detecting by the inspection stations. You can always use the excuse of cleaning the terminals. Why not find out the cause of the check engine light?

olds1968

when you disconnect the battery the modules reboot and run on a preset parameters and have to reset so when they hook up the computer the modules will show not ready. drive the car for 60 to 100 miles and the monitors should be ready and if the problem is still there the light will turn on again.

VikingBlue

cutlass...I know what the problem is....oxygen sensors...which is why my second nissan (this pathfinder) will be my last. Never had issues in other makes i have owned but this and the '98 maxima were O2 sensor nightmares

I am tired of having them replaced.

So I want to get thru inspection...and sell this car before the 2014 inspection

joe_padavano

This depends on the year and model. For OBD-II GM cars, simply disconnecting the battery will NOT erase the ECU memory. Failure codes and drive cycle performance are stored in non-volatile memory. More to the point, even if you use a scan tool to erase the stored codes and drive cycle memory, the test station can tell that the drive cycle has not been completed and will tell you to come back another day after you've driven the car more.

RetroRanger

stay away from volkswagons and their audi cousins if you dont like CELs...a common refrain on volkswagon for sale ads "No CEL on" (or conversely CEL on LOL)....Ill bet my VW CEL was on at least half the time I owned it (10 years) despite fixing what was wrong I was almost guarenteed in 6 months that thing would be lit again

pogo69

96 and newer you can fool the inspection...driving about 10 miles min. including some highway speed will put enough info into the pcm this is providing you,dont set a code in that time....this has worked for me going thru emmisons

joe_padavano

You can't "fool" anything. If the problem is intermittent or only shows up under very specific driving conditions, you CAN get lucky and complete the pre-determined drive cycle without triggering a code. The drive cycle varies by year and model and usually takes more than ten minutes.

pogo69

Just reported what i have done in the past joe...discinnected battery several hours when reconnected the check engine light was off went to emissiins and the report stated not enough cycles in the pcm.....so i went home disonnected battery overnite and reconnected, the check engine light was off,put maybe 20 miles on it went back to emmissions and passed...somebody or something was fooled, this for a fuel purge canister code and again for an egr...yes an intermittent

gearheads78

In Texas if you disconnect the battery it will not pass because of the "not ready" status. Usually takes a mid tank of gas and 70-80 miles for all the self checks. It needs to be done in a couple of cool down cycles and a full or empty tank will let the car check itself.

pogo69

Also in my case the egr problem but the po442 is still active, now when i drove straight thru to florida the light never came on...but its back on now...i have gone thru two emission inspections and passed i suppose" your results will vary"

2Olds4U

VikingBlue, we really need to back up a bit. What was the code, or codes, that set the CEL, MIL, or whatever anybody wants to call it?
If the light came on, there was a reason. It could be anything from a loose gas cap to being too cheap to put premium fuel into it and so on and so on.

You said "non Olds". What make, model and year? Let's not deal in the dark.

As Joe and other have said, disconnecting the battery will accomplish little. When a fault is erased, it automacically resets the drive cycle parameters to a binary 1111111, or close. The ECU monitors the various emmission related functions, such as oxygen sensor heating, Oxygen sensor performance, Catalytic converters, Evaporative Emmissions (there are 2 tests, 1 for leakage ie: loose gas cap, and fuel tank venting, like a bad purge valve or leak detection pump, etc.), secondary air (also known as an air pump). When all is set and you go for an OBDII test, those parameters will go from 1111111 to 0000000, indicating no faults and readiness set.
This may be more info than you need, but I thought you should be aware of how the system functions.
AZ will be all to happy to scan your car for free and sell you a bunch of stuff that will not fix your car.

And RetroRanger: I stand by my words. If you have a VW or Audi and the MIL is on, there is a problem. It may be hardware or software related, but there is something wrong. I have specialized in these cars for 35 years and if it comes on and you give me the code, I can tell you within 98% what is wrong with that car.
And did you know that VW and Audi are the ONLY makes to my knowlege that you can, with the correct software, force the readiness codes to set without leaving the driveway?

Paul

RetroRanger

Hi Paul

Thanks for your offer, I'm in ma too. After owning many vws and audis over the years, I have decided that even tho I love them they are too needy for my tastes, that coupled w VWOAs and the 3 somewhat local dealers attitudes towards in warranty repairs cemented my decision to not own another one. Thanks to similar forums as this one and a very helpful VW tech fromWV I was able to solve all my CEL light issues, but every time it went off I knew it wouldn't be long before that thing would be on again.

I sold my last VeeDoubleU in 2004. Since that time the only CEL I've seen has been on initial startup. I've driven the same ford for 10 yrs 120k miles, along w wife's Mazda, Volvo and Toyota no cels !!!

Dean

VikingBlue

Paul---2001 Pathfinder...

stan 65 cutlass

google year and model of vehicle," check engine light on "some cars have theyre own onboard code readers and the ability to reset the chek eng lite as well, wifes 95 maxima does

gearheads78

Only works on 95 and older. 96 and newer is OBDII

2Olds4U

And what were the "P" code(s)?

nsnarsk65cutlass

Disconnecting the battery on obdII all it does is resets the monitors,if not driven to complete them and theres a fault the mil will come back on,if no fault then not a problem.If you have to do smog test here in CA they hook up to dlc and will or wll not have X amount of monitors closed if you don't you failed.Plain and simple as that.

pogo69

As far as the original post is concerned...dissconnect it overnite drive it the next day for a while say 20 miles go thru your emission inspectio if the light is off and just see what happens...if you pass great!!! If not you will get a retest right? And the you will have to fix it

VikingBlue

OK so long story short a month ago I needed to get thru inspection and had the CEL light on,,,so i went to Autozone to get the code/problem identified.

was told it was oxygen sensor, which is what I expected bc thaT's all that ever seems to go wrong with my Pathfinder and every other Nissan i've owned (and will never buy another).

anyhow, brought to mechanic to fix and told him I already had it tested and it came up "oxygen sensor." He told me that it came up "camshaft position sensor" on his reader and charged me a lot to fix that...and said I needed to drive at least 60 miles for the computer to reset and clear the error code.

well, at about 80 miles post-repair (I guess as soon as the computer reset) the CEL came back on...and brought to same mechanic...and now he tells me it's oxygen sensors...like I advised the first time. So it seems to me he fixed something that didn't need to be fixed and my initial problem remains.

is it reasonable to expect him to fix this for free since I told him what the problem was the first time but he replaced something else ? Or is it more likely that there were two problems all along and he did fix one...and therefore I should pay for the other as well (oxygen sensor).

stevengerard

You would think there were two problems but you should at least go back and ask. I'd wait until one of the mechanics on here responds to you. On our Suburban, we left the cap open on the gas tank. CEL turned on, I replaced the cap, light turned off. Had to bring the car in for something else, a few days later, normal mechanic was too busy that day and we needed it fixed right away. This other mechanic told me the check engine light was recently on, and said that's because of the plastic intake manifold leaks on Chevy's. I said yep, I heard of that, when the light goes on we can check it again. Two years later the light has not gone on again.

Point is I don't trust all the codes or mechanics. But I do trust some mechanics, lots of good ones out there.

joe_padavano

Yes, leaving the gas cap off will trigger an EVAP system code, and yes, putting it back on correctly will allow the light to go back off. The OBD II system is smart enough to recognize when some code-setting problems are corrected and will reset the system if there is no fault detection after a certain number of start/stop cycles. Any fault that does set a code, even if it's later corrected and the computer turns the light off, will be retained in a history file for a period of time. It's very possible that multiple old codes are stored in the history file and it's possible to retrieve them with a scan tool. Unfortunately, if there's a history code but no current code, one can only act on the information available in the history file. Also, keep in mind that there are still many, many faults that don't or can't set a code, like dirty injectors or a plugged fuel filter. This is where real troubleshooting skill (as opposed to reading codes and replacing parts) comes into play.