Check Engine Light P0456

Elt31987 · **Posted:** Wed Sep 29, 2010 9:07 am

So got my first CEL since i bought it 2 1/2 Years ago. P0456. After reading its referring to a small leak in the Evaporation System. First everyone says to check the Gas Cap which i turned off the engine, Took the cap off, put it back on and made sure it clicked a few times. The cap is a Mopar Locking Cap that I've had since i bought the Jeep. After removing the cap and putting it back on the light is still on after i drove about 22 miles to work. I don't know how long it takes for the code to disappear if that was the issue but the light is still on. So basically I'm going to hope its off when i leave work today and if not ill put my girlfriends Locking Mopar Cap from her Patriot on mine and see what happens. Any other suggestions to look for?

cgreen · **Posted:** Wed Sep 29, 2010 10:42 am

Somebody double check me but I think all OBDII codes are stored for something like 80 warm up cycles.

Before I bought my own code scanner, I had pretty good luck going into AutoZone and asking to borrow their code reader while they were too busy to come outside with me. They aren't allowed to turn the Check Engine light off but if you get someone to give you the scanner while they are busy you can do it yourself. You could also unhook your negative battery cable for a few minutes to clear the code, but your truck may run slightly different until your ECM relearns your driving habits, although most people will not notice much of a difference.

If you watch the sales at Harbor Freight you can buy a simple reader that will erase codes for about $30 with one of their coupons.

richd · **Posted:** Wed Sep 29, 2010 2:56 pm

Here is how to erase code if you dont have a scanner,plus it shows how many starts to get the PCM ready:

To reset your engine codes:
Remove the negative terminal of your battery (10mm wrench).
Turn your ignition key to START and hold it there for about 15 seconds.
Turn your ignition key to OFF and remove it.
Connect the negative terminal of your battery.
Start but do not hit the throttle. Idle for about 10/15 seconds then turn off.
Restart the truck and drive as usual. It will take at least 12 starts and 48 miles to fully retune the computer. Hard Codes leave a shaddow for 40 full cold starts.

Albert · **Posted:** Wed Sep 29, 2010 2:59 pm

richd wrote:

Here is how to erase code if you dont have a scanner,plus it shows how many starts to get the PCM ready:

To reset your engine codes:
Remove the negative terminal of your battery (10mm wrench).
Turn your ignition key to START and hold it there for about 15 seconds.
Turn your ignition key to OFF and remove it.
Connect the negative terminal of your battery.
Start but do not hit the throttle. Idle for about 10/15 seconds then turn off.
Restart the truck and drive as usual. It will take at least 12 starts and 48 miles to fully retune the computer. Hard Codes leave a shaddow for 40 full cold starts.

Thanks richd. That is good to know...... :JEEPIN:

Elt31987 · **Posted:** Wed Sep 29, 2010 6:29 pm

So i inspected the Evap Box and hoses and didnt see any holes or tears etc. BUT, i could smell gas from the Cap so i think its leaking. So i disconnected both battey terminals for 30 minutes and threw my original Gas Cap on that i found laying around and so far so good. Ill keep you guys updated over the next week. Wish me luck.

Idaho08KK · **Joined:** Tue Aug 18, 2009 12:14 am **Posts:** 29

With the newer CDJ products, unhooking your negative battery cable no longer erases the DTCs in your PCM. That used to work with the older ones, but not anymore.

Elt31987 · **Posted:** Thu Sep 30, 2010 6:51 am

^^ Well don't know but when i reconnected the battery after 30 minutes the light was off so it did something.

richd · **Posted:** Thu Sep 30, 2010 2:14 pm

Idaho08KK wrote:

With the newer CDJ products, unhooking your negative battery cable no longer erases the DTCs in your PCM. That used to work with the older ones, but not anymore.

The procedure I showed does work.I hear about it all the time.I also know it works on Chrysler 300,Chargers,Magnums,these are fairly new products.

tjkj2002 · **Posted:** Thu Sep 30, 2010 8:57 pm

richd wrote:

Idaho08KK wrote:

With the newer CDJ products, unhooking your negative battery cable no longer erases the DTCs in your PCM. That used to work with the older ones, but not anymore.

The procedure I showed does work.I hear about it all the time.I also know it works on Chrysler 300,Chargers,Magnums,these are fairly new products.

It may turn off the MIL but the code will not be erased,hard fault codes can not be cleared unless by a scanner or a certian # of no-fault drive cycles.

richd · **Posted:** Thu Sep 30, 2010 11:36 pm

This is from Allpar,best known for everything MOPAR:

Resetting the computer
Normally the computer will eventually reset itself; you can also use a scan tool. (See our transmission repair page for information on resetting the computer's transmission information.) Disconnecting the battery for a few minutes generally resets the computer, though it also means losing clock settings.

I found this at a site called GENO"S Garage:

If any problem is repaired or ceases to exist, the fault code stored in the PCM will be erased after 51 engine starts. All stored codes will be erased if the battery is disconnected for 15 minutes, but a fault code 12 will be set when the battery is reconnected..

JeepinJarhead03 · **Posted:** Fri Oct 01, 2010 1:09 am

Richd you said it yourself "Hard Codes leave a shaddow for 40 full cold starts." that's what Troy's talkin about.

All depends on the classification of the code, for instance it'll refuse to be "ready" for OBDII inspections after a battery unhook for ~3 cold/warm cycles + 60 miles, but just 60 miles won't do it, and you can get by with less than the miles but the cold / warm cycles have to do their thing or it'll never go green

I drove mine for a cold/warm cycle, plus 140 miles and it still wouldn't go ready, drove it 15 miles home, tried again the next morning and it was good to go

Your method will work for soft codes, stuck gas cap mil light, etc

Will kill the mil light, but anything emission related other than gas cap, it'll retain it and depending on the cycles will fail it on obdii inspection

tjkj2002 · **Posted:** Fri Oct 01, 2010 7:24 am

richd wrote:

This is from Allpar,best known for everything MOPAR:

Resetting the computer
Normally the computer will eventually reset itself; you can also use a scan tool. (See our transmission repair page for information on resetting the computer's transmission information.) Disconnecting the battery for a few minutes generally resets the computer, though it also means losing clock settings.

I found this at a site called GENO"S Garage:

If any problem is repaired or ceases to exist, the fault code stored in the PCM will be erased after 51 engine starts. All stored codes will be erased if the battery is disconnected for 15 minutes, but a fault code 12 will be set when the battery is reconnected..

Fault code 12 is OBDI which means it's a '95 or older vehicle.You can get OBDII code P1684 on newer Chryslers just by unhooking the battery.

Check Engine Light P0456

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