Strange, Odd Fix........


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Old 06-22-24, 04:50 AM
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Strange, Odd Fix........

2007 Dodge Ram 1500 5.7 Hemi.
For reference: The odometer (digital) space is also an information display.
For the last 10 - 15 years "gascap" has been showing the the odometer/information center. I changed the gas cap back then but obviously, that didn't fix it. In my opinion, there's a leak somewhere. Rubber line losing seal, etc.
Fast forward to last week. Alternator went out. Was on the road so, called a tow to my mechanic. They replaced the alternator after some tests to ensure the problem.
When I picked the truck up & started it, I noticed the message was gone. I thought, well they probably disconnected the battery, then hooked it back up & it reset the code... It'll be back on by the time I get home. (I'm not sure they disconnected the battery, that's just a guess)
A week later, my wifes Yukon needed some attention so we took it in. Picked it up a couple of days later. My odometer is still showing mileage. I asked the owner if they did anything to fix the message/code/error, like replace a rubber line or something & just didn't charge me for it. He said no. Only thing they did was change the alternator (& replaced the belt for PM). Nothing else. We discussed it. He's kinda puzzled also. We both agree, this is a vacuum issue... has nothing to do with changing an alternator.
As strange as changing a tire, now the horn works.. (Example only - one doesn't affect the other).

We have agreed to conclude its just a miracle...lol. But it's really been on my mind.
In 15 years, I have disconnected the battery countless times. Even sometimes to reset codes. I've replaced the battery 2 times in the last 15 years. It has always come back on within a few minutes to a couple of days. It's been two weeks... still the odometer is showing mileage. I'm thankful its working, but just one of those nagging issues I can't figure out.
 
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Old 06-22-24, 05:21 AM
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For several yrs the gas cap light has been on my jeep. Replacing the cap didn't fix it. From what I've read replacing the tank is needed ........ but it doesn't leak [maybe a tad bit of fumes??] So I just live with it.

Maybe the fuel line got bumped in the process ?? ..hope your warning light stays off!
 
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Old 06-22-24, 06:05 AM
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Yeah, Mark, I dont know your situation but generally speaking, I doubt the tank needs replacing. It could but IMO, it'd be highly unlikely unless the tank was damaged or has rusted etc.
They way this system works in general terms is that when you start the vehicle, it pulls a vacuum as such. If it doesnt pull a vacuum, that stinkin light will show up (throw a code). normally, more times than not, its a cracked rubber return line etc, Some sort of rubber line. As you well know, those rubber lines underneath an off road vehicle especially, gets a lot of dirt, mud etc & dry rots the lines & they crack. Now the system can't pull a vacuum.
During design, it was intended that the gas cap seal would be the most common cause/area for a leak. Which turns out is probably the least likely. I've never experienced a gas cap leak causing this issue. Doesnt mean it doesnt, but in all my discussions, I've never run across a gas cap leak. Its usually a rubber line somewhere.

A fuel tank is certainly an option, but, it would not be in my top 3 or 4 things to go to.

Gas cap seal, rubber line, filler hose, rubber gasket around the fuel pump etc...
 
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Old 06-22-24, 06:27 AM
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probably may come back on eventually so I would not say that its fixed really.
 
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Old 06-22-24, 06:48 AM
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And I agree Alan....... That's what I'm kinda afraid of. It's just awfully unusual, that it hasn't resurfaced over a couple of weeks. But honestly, I'm afraid you're right.
 
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Old 06-22-24, 01:07 PM
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I have a 2008 RAM 2500. Was getting a P0456, small leak from evap system. Replaced dap since that is a cheap fix. Cleared code, it came back, ignored it, round and round. Had other issues like a misfire and knock senser. Did other repairs and now its working fine and the evap code has never come back,

I don't think one thing had anything to do with the other. If you're not seeing the warning and the truck runs OK, thank the auto gods. If you're really worried, get a scanner and see if any pending codes or some other clues. But if it were me and the warning has gone away and the truck runs ok and the mileage seems to be normal, I wouldn't worry about it and take the win.
 
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Old 06-22-24, 02:02 PM
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Whittsend, thanks for your input. Oh, I'm not worried. It's just more of a curiosity than anything. Its gone so far and i'm good with that. My post was just out of curiosity if anyone had any theory about why. Not important really.
 
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Old 06-26-24, 12:31 PM
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I think a bad alternator/regulator can cause electrical problems and electrical problems can cause computer problems. And computer problems can cause false error messages.

Could your alternator/regulator actually have been overcharging/undercharging the battery for a long period of time, and then the alternator/regulator just finally quit? But during that period of usage the "gascap" sensing and processing hardware was the most sensitive to slightly out of tolerance voltage (maybe because of a faulty intolerant design) and thus was the only function affected while the faulty alternator/regulator was being used?

Well I guess maybe I really don't even believe that one myself - lol! But who knows, strange things can happen.

But I know what you mean, it doesn't give you a "warm fuzzy" when something like that just magically disappears.
 
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Old 06-26-24, 03:08 PM
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Well, to update.. ..... its back on as of about 3 days ago. Oh well it lasted about 3 weeks.

My best guess is that when he changed the alternator, he disconnected the battery for safety & it reset the codes. Only plausible thing I can come up with.

Thanks everybody.....
 
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Old 06-26-24, 07:56 PM
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The mileage is stored in the ECM and is held regardless of no power.

The code is slow or small leak. Typically with most vehicles it's the gas cap is leaking or is not on correctly.

Not so on the Ram trucks.

There is an air purge valve in the rear of the truck that can go bad.
That's the easy fix. If that purge valve fixes the problem you're all set.

However.... the most common problem is at the top of the tank requiring tank to be dropped.
My neighbors truck and my fathers 2013 both needed the tanks dropped.

 
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Old 06-27-24, 02:52 AM
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Yeah, thats why its been like this for many years... lol
It's not that big of a deal. I can see the mileage when I turn the ignition to the on position before starting. If I ever have to have a fuel pump etc, I'll get'em to check it out.
 
 

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