Clear OBD (check engine) codes by disconnect battery

[Hckynut56]

A new member here. Sorry if I'm beating a dead horse here.

I have seen several mentions of disconnecting your negative battery terminal for a time period to clear your OBD codes.
I live in Illinois and need to pass a EPA test. They now check for OBD's. Will the disconnect clear everything ? Or at least enough to pass ??

Comments !

Thanks to all in advance.

[mmahamm]

It depends a great deal on what problems there are. Some problems will cause the Check Engine Light to turn on right away, others take some time. So depending on the problem, the light may turn on, on the way to the inspection station. In any case, the OBD will show that the battery was disconnected within the past 50 starts or so.

[Jeepman]

A new member here. Sorry if I'm beating a dead horse here.

I have seen several mentions of disconnecting your negative battery terminal for a time period to clear your OBD codes.
I live in Illinois and need to pass a EPA test. They now check for OBD's. Will the disconnect clear everything ? Or at least enough to pass ??

Comments !

Thanks to all in advance.

X2 (Same as response to EGR Valve Post)

Disconnecting the battery (say for 10 minutes) will clear the codes if they are no longer applicable such as glitches or the problem was remedied (replaced upstream oxygen sensor for example).
If the EGR Valve is indeed faulty, the code will reappear and the check engine light may come on. After a battery disconnection, a code P1684 ("battery disconnected .......") will show up if you access the computer (using key dance method) and will disappear after 50 restarts. Otherwise you will get "donE" if no detectable faults are present.

[DaveKG55]

It depends a great deal on what problems there are. Some problems will cause the Check Engine Light to turn on right away, others take some time. So depending on the problem, the light may turn on, on the way to the inspection station. In any case, the OBD will show that the battery was disconnected within the past 50 starts or so.

I've disconnected my battery on several occasions over the past few years, including recently (when working on heat/AC issues under the dash) and my check engine light never did turn on (even the radio station presets were still good). The battery was typically disconnected for at least 30 minutes, often much longer (hours). However, I never did the key dance trick to see if of any codes were present (such as the one referring to the battery disconnect in the last 50 starts). It may have been present but the Check Engine light never activated so I didn't check.

Oddly enough, I once had a check Engine Light condition and the keydance code was the "battery disconnected" code (1684?). But that occurred nowhere near anytime that I had disconnected the battery.

Just FYI.

[Jeepman]

I've disconnected my battery on several occasions over the past few years, including recently (when working on heat/AC issues under the dash) and my check engine light never did turn on (even the radio station presets were still good). The battery was typically disconnected for at least 30 minutes, often much longer (hours). However, I never did the key dance trick to see if of any codes were present (such as the one referring to the battery disconnect in the last 50 starts). It may have been present but the Check Engine light never activated so I didn't check.

Oddly enough, I once had a check Engine Light condition and the keydance code was the "battery disconnected" code (1684?). But that occurred nowhere near anytime that I had disconnected the battery.

Just FYI.

I know what you mean. The "check engine" light doesn't come on for P1684 normally. That's okay.
If you check for fault codes (key dance method) and find P1684 showing up, there likely has been a power disruption of some sort, maybe even a loose battery connection, or a "quick learn" (if one was performed recently) that triggered it. The fault, really, is power to the TCM has been interrupted. For possible reasons, check this site.
http://dodge.justanswer.com/question...3-t-c-3-8-know

[nice05sxt]

unhooking your battery will clear your computer's memory of stored codes. your computer tests different systems on your car on a preset "drive cycle"- each test runs when different driving conditions are met. some tests run as soon as the key is turned on, some take several key cycles and cold soak periods (car sitting overnight). the results of these tests are stored and processed in your car's pcm (Powertrain Control Module aka the computer)these results are what the pcm uses to determine whether or not to illuminate the check engine light (aka MIL or idiot light or SES light- all the same) when you take your car in for emissions, the computer the shop uses checks your pcm for readiness monitors (the pcm's list of completed or not tests) the emissions test will only run if all of your monitors are set, so by unhooking the battery your car will show up as "not ready for testing" and the garage will tell you that you unhooked your battery and send you on your way to come back in a week or so. the best bet is that Autozone does free scan tests, there are also some others that do this too. they will even try to sell you the part they think you need!

[xitrum08]

If you want to erase the code before go to emission test,you should buy the DRB ll scan at Sear,it's about $80,after erase the code you can return it if you want to,I did mine before.
good luck

[rabbler]

It depends on how thorough the emission test is.
It differs by state.
In some states as long at the MIL isn't illuminated but working (bulb check) your good.

Others will test the system and see if it passed all the self tests. Clearing codes or disconnecting the battery just before testing will automatically fail.
And finally some states will test (sniff) the tail pipe and measure the harmfull emissions. If your levels are too high...You fail