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P1684 & check engine light issue

Discussion in 'Repairs, Maintenance, Help' started by dno36, Feb 9, 2015.

  1. dno36

    dno36 Active Member

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    Greetings all,
    One of our vans is an '03 T&C base 3.3L flex fuel. Currently at 136K mi.
    From time to time I have used E85 fuel in our 3.3's when it is much less cost than regular fuel.
    Last Friday was one of those days.
    About 1/2 way into the day my check engine light came on.
    Nothing seemed to change at all with the driveability, even after doing numerous stops over a 150 mile total day. No issues at all.....
    However, the next morning, it was difficult to start, popping and not starting numerous times before it finally just ran normally ( all of my 3.3's always started perfectly)....It ran fine all day without issue.
    I checked the code and it was P1684.....battery disconnection, me.... never...so I started reading here and read there and over there too. Power loss to one of the "CM's" OR something major??
    Again the next morning, difficult to start, driving normally.
    Today, after a difficult start, it continued to 'miss' about a block down the road, then finally smoothed out and ran normally. A progression to a worse issue, so now I worry.....

    1. Could this be related to the E85 fuel??
    2. Where would 'you' start to look with given symptoms?

    TIA

    Dean
     
  2. Rick Anderson

    Rick Anderson Well-Known Member

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    Code P1684 is very common and many Chrysler vehicles will have this fault code stored with nothing discernibly wrong with the vehicle. It should NOT light the CEL, so I'd suspect there is another fault code stored that set that CEL.

    Code P1684, may be described as the battery disconnected within the last 50 key cycles, but when you start the motor the voltage on the battery drops considerably, that likely makes the PCM see it as an interruption of power and sets the code. I have the code for years, always started reliably, when the battery finally gave out and I put in a new battery the code went away. Unless you have battery power or electrical issues, most people ignore the code P1684.

    Alcohol is notorious for poor starting and running in cold weather and cold motors. The E85 could be the cause of your problems or at least contributing to a problem somewhere else. I would read the codes and again see if there is another one stored in addition to the P1684, I doubt the CEL came on and stayed lit for the P1684. If the PCM is dumping the stored codes, the P1684 may be a clue, electric power is being interrupted to the PCM. A PCM that has reset, i.e. dumped its volatile memory, will also have dumped all of its adaptive correction data. A reset PCM will often have a hard time starting and stall, until it makes some adjustments. So a possible place to start is looking for electric problems or a weak battery.
     
    floridaman2013 and ImperialCrown like this.
  3. valiant67

    valiant67 ...

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    For whatever reason the Chrysler logic often sets the battery disconnect code when another code was set. How did you read the codes?
     
  4. ImperialCrown

    ImperialCrown Moderator
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    I agree. A P1684 isn't necessarily a 'battery disconnect' code, but somehow the battery power to the PCM was lost. This may be a wiring harness or connector problem. (It can also be an internal PCM connection (solder joint?) problem, but rule out anything outside the PCM first).
    The location of the battery close to the PCM makes any unsealed connectors prone to corrosion from battery acid misting. Look carefully at the connector terminals. Unplug and re-plug connectors for inspection and to 'scrape' a new fresh contact between the terminals as you reconnect them.
    Clean battery terminals are a must. Take them off and actually brush or scrape the insides of the terminals and outsides of the posts until you see shiny lead.
    As stated, when the PCM loses battery back-up, all memory and settings are lost. This may have also wiped out any other fault codes that are pertinent to the hard starting issue. When 'learned' idle speed (AIS motor position) is forgotten, it may start hard without your foot on the gas. A clean throttle body bore and blade is important and may help with the hard start.
    The 'pop-back' (a backfire through the intake) may be a lean condition. The PCM should adjust for the E85 when starting, but if that memory is lost, it may start hard.
    http://www.aa1car.com/library/battery_disconnect_problems.htm
     
  5. Rick Anderson

    Rick Anderson Well-Known Member

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    Keep in mind, the PCM is a solid state electronic aka semi-conductor electronics. Semi-Conductors (computer chips, transistors, etc) voltage or current drops to low on these items, it won't even flow, you get all sorts of logic errors as well, semi-conductor equipment will just go dead if the voltage drops to a certain point. That is why you see things like the BCM turning wipers on by itself when the battery is about to go dead.

    I don't know, what I have seen, is codes P1684 or code 12 on vehicles with older but still seemingly well working battery's, then when replacing the battery, the code P1684 and code 12's go away. No other signs of electrical problems.

    My theory, during start the voltage drops drastically for a moment till steadying out, that downward spike of voltage, with a weaker/worn battery could be below the threshold for the PCM, the PCM dies for a moment until the voltage comes back up and steadies out and the engine starts. But the PCM would set a code for power interruption.

    I have no idea if this is true, but it makes sense and fits what I've seen and know (which I don't know or seen everything). You've got a aging/worn battery that might still have several years of life left in it, it could be behind the momentary power interruptions to the PCM that set the Code P1684, and there is nothing wrong with the car other than the battery is showing enough age that when you engage the starter its initial voltage drop is now low enough to interrupt the PCM for a moment.

    The code P1684 will NOT lite a CEL and keep it lit, like the OP observed. So code P1684 might be a clue there is something electrical could be at the root of this.

    If the OP forgot to tell us, that he has had the battery go dead several times in the last month, then I would be pointing all of this at the battery and getting a load test. But he hasn't said that, so maybe there is a physical problem with the electrical system, maybe it is just a minor/intermittent short from corrosion or road salt in the engine bay and wiring. Or they could be totally unrelated. On the Neon's, cleaning the battery posts and terminals solved a lot of electrical issues, most cars corrosion on the battery terminals is too small of a factor to ever cause problems, but its one of the those things it can't hurt to do, as well as do a load test on the battery.
     
  6. dno36

    dno36 Active Member

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    OK troops,
    Here's the update.
    I got the original code from the 'key-flip' method while I was away. The result was the P1684 code, and that was the only code.
    I used my OBD scanner today and received a P0171 and only the P0171(Lean condition). Nothing in the history.
    Well the lean condition makes sense with running the E85.....but why did the 3.3L flex fuel engine not adjust for the E85 like all the other(8 total) times I ran E85???
    I cannot recall if I ever ran E85 in this van before.
    I have never touched the battery on this van, ever. Bought in 06/14 with 93K, now has 134K....yes, I drive a lot. Battery was new in Feb 2012. All connections at top are good.

    Just for kicks I did the 'key-flip' test again and the P1684 code is still there....?? Only the P1684, nothing else.
    Plugged my scanner back in and it still reads only the P0171 code.
    I would have a tendency to believe my scanner with the results given.

    So... Being that I had 285 miles on this tank of about 80% E85 fuel, I filled it with 16.6 gallons of regular BP fuel in it today. I have only driven about 10 miles and the code was still there.

    Should I clear the code?
    Anything else I should watch out for?

    Thanks for all the help

    Dean.
     
  7. Doug D

    Doug D Virginia Gentleman

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    I'd clear the code and see if it comes back.

    Does the owner's manual say anything about switching between E85 and E10? I could swear I read you should be near empty when switching from one fuel to the other, but I'm not sure.
     
  8. Rick Anderson

    Rick Anderson Well-Known Member

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    I'd ignore the P1684 and concentrate on the P0171. Your battery may be showing a little age, but if you had no electric or battery problems up to this point, it probably is meeting your needs just fine and you're getting that nuisance P1684 like many Chrysler owners do.

    I'm NOT an expert, so take this with a grain of salt, alcohol runs at stoichiometric just like gasoline, it just takes nearly twice as much alcohol as gas per air to reach stoichiometric. So just because you're using E85 that should NOT make the motor sense lean. The motor is likely sensing lean because some malfunction is causing it to run lean.

    I could see switching back to gas working, at least E10, because if you have a fuel supply problem (a weak fuel pump, a weak injector, dirty injectors, clogged fuel filter, etc) using gasoline would reduce the fuel flow demand to nearly half what it was while using E85. Of course that is only fixing the symptom, NOT the problem.

    Ethanol has its own set of drawbacks, starting in cold weather and running cold engines is some of them. It also attracts and absorbs a lot of water, more so than gasoline. A bad tank of E85, that was contaminated with water might cause this as well.
     
  9. dno36

    dno36 Active Member

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    Friday 2-13 update,

    Ok , the regular fuel has brought the car back to normal.
    Starting Wednesday, the next day after re-fueling with regular gas, it started just fine, however the CE light was still on.
    About 65 miles into the tank of 'regular' E10 gas the check engine light went off and all is good and right with the world again.

    Maybe I did get a poor batch of E85?
    I realize that E85 is very anhydrous, however, I drive big miles and my tank-fulls do not last long at all.
    Right now our regular fuel is at $2.45/gal & E85 is at $1.79.... guess I'll just stick with good 'ol E10 and not mess with it anymore.....or maybe I should try a different station for the E85??

    Other than this check engine light, this van has run flawlessly, however, this is the worst mileage of any van we have ever had with a 3.3L. Around 20.8 MPG on my all-around driving. My '95 was over 23 MPG and the '99 was almost 23. Both of our 3.8L's (2003 & 2006) are in the high 19's around town.

    Many thanks
    Dean
     
  10. Doug D

    Doug D Virginia Gentleman

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    Just curious - what was the fuel mileage when using E85?

    It does sound like it was ultimately an issue with the E85.
     
  11. ImperialCrown

    ImperialCrown Moderator
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    Or as you mentioned a bad tank of E85?
    Here in the Northeast deep-freezes, the underground fuel tanks can rupture and allow ground water to seep in. Usually gas stations will be honest with customers when reports of this has happened. It has ruined fuel systems and if say, 100 customers claim damages, it can get expensive.
    A fuel sample can be taken. Gasoline and water will separate. Water will sink to the bottom.
    E85 will hold a lot of water in suspension and may appear cloudy?
    Most in-tank fuel pumps use a 10 micron pickup filter. That should stop water, but fuel may not be able to get around the water to get pumped forward (lean).
    http://continuouswave.com/whaler/reference/fuelFilter.pdf
     
  12. pt006

    pt006 Active Member

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    DNO 36; E 85 has less energy per gallon than E 10. Depending on how much your mileage drops, it may be cheaper for you to burn E 10.

    ICrown; in some N.E. states, gas stations and underground home heating fuel tanks were required to dig up their old fuel tanks and replace them with double walled fuel tanks. I think they were steel tanks covered with a fiberglass outer layer.[a guess]. There is probably some method to tell if they spring a leak. The gas stations would be shut down for a few months and be surrounded with the yellow tape.
     
  13. Gerry G

    Gerry G Well-Known Member

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    Is there ever a good batch of e85? Sorry, topic for another day.

    Gerry G.
     
  14. Gerry G

    Gerry G Well-Known Member

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    I have not seen that type of price differential between e10 and e85, over 60 cents, which raises a flag for me. I have seen 20 - 30 cents difference and it is possible you are buying your e85 direct from an ethanol producer. In fact the price you note for e85, $1.79, is not much higher than the market price for a gallon of ethanol (about $1.40) which seems to indicate that (and there is a major surplus of ethanol these days). I suspect what you got was an adulterated batch of e85 that was not blended properly, possibly too much ethanol.

    My 2 cents worth.

    Gerry G.
     
  15. Rick Anderson

    Rick Anderson Well-Known Member

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    I would still try to pull up the stored fault codes and check them, see if you have a problem that may come back or if it was something that might indicate it was the E85 all along.

    Oh, BTW, my '02 Caravan Owner's Manual stated that if you use E85 as fuel, you should get a special motor oil from the dealer and use that instead of normal motor oil. I'd look into that if you're going to be using E85.
    I noticed the same between our '91 and '02 Caravans, you can feel by the handling the later vans are much heavier as well. This has been true for all car lines, they have gone up in weight from safety regulations for higher impact resistance and mandated additional safety equipment, as well as general consumer demand for more and more trinkets and gadgets. Also the higher and higher pollution restrictions on the engines have dwindled their mileage as well.
     
  16. dno36

    dno36 Active Member

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    OK all,
    The fault code went away and has not returned.
    Even adding the 14+ gallons of regular fuel had the light gp off in about 60 miles and has not returned.

    Our E85 prices seem to hover between 15 & 25% less than regular.

    I am just confused as to why my 3.3L flex has reacted in this manner with E85??

    Thank You all.
    Cheers
    Dean
     
  17. dno36

    dno36 Active Member

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    Hey Doug,

    My mileage was around 18 for teh tank with the E85, which seemed quite high to me.
    My other FF 3.3's usually ran around 16mpg.
     
  18. Doug D

    Doug D Virginia Gentleman

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    Considering the '00 T&C Ltd AWD 3.8L (Not Flex Fuel) we use to have averaged 16 mpg with E10 in local driving I would expect only 12-13 mpg with E85. Would expect 18 or so highway with E85.
     
  19. Rick Anderson

    Rick Anderson Well-Known Member

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    Seeing how mileage is likely reduced more than price difference in the fuel, you may NOT be saving any money.

    There may have been a problem with the E85, i.e. contamination, the distributors are very familiar with the precautions for gasoline, but perhaps NOT E85 and it might have gotten contaminated along the way.

    You have to burn more alcohol than gasoline, to get a stoichiometric A/F ratio, that means the fuel injectors and fuel pump have to move more fuel. Perhaps a wearing or unnoticeable malfunction in the fuel system doesn't provide the extra volume needed for the alcohol, but can do it, for gasoline?
    Has the O2 sensor been changed during its life? Maybe it has an aftermarket O2 sensor that won't work properly with alcohol, etc.
    And its totally possible, since the vehicle has run on gasoline for so long, it might take some time to get the cob webs out of alcohol and functions and react properly.
     

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