Chrysler Repair: 2001 T and C LXI: Speedometer Issue, trip odometer, explanation fo

Question
QUESTION: Recently, the speedometer on my 2001 Town and Country began moving up to 5 or 10 mph when the car is placed in gear, even though the car is not moving.  Sometimes the car seems to surge a bit when this happens.  As soon as the car begins moving everything seems to be fine.  I thought it might be the output speed sensor so I replaced it, but that didn't help.  I also calibrated the instrument cluster by pressing the trip odometer for 5 or 10 seconds but that didn't help.  I checked for codes but there are none.  After further investigation, I noticed that the problem is much more evident when the a/c is turned on and worse yet when the a/c and headlights are on.  For example, if the a/c is off and I put the car in drive the speedometer will rise to 5mph and then fall back to zero within 2 or 3 seconds.  If I then turn on the a/c the speedo will rise and bounce between 5 and 10 mph for an extended period of time.  I am wondering if this is an alternator issue.  I checked the battery with the car off and it puts out about 12.4v.  I checked the voltage with the car running and it registers about 13.5v.  I put the car in drive and turned on the a/c and headlights and it maintains about 13.3 to 13.4v.   Is it possible that this is the problem?  Any help that you can provide would be greatly appreciated.  Let me know if there is any other info that would help to diagnose the problem.  Thank you.

Dave

ANSWER: Hi Dave,
When you pressed and held the TRIP ODOMETER RESET button did 'Sof and a number' appear in the window? Then did you release the button? Then did either any numbers appear/"end" appear in the window?
Then did the speedometer, tachometer, fuel gauge and temp gauge go through a set of calibration point readings (for the speedo did it read 0,20,60,100?). If so then the speedo is calibrated, if it didn't read those settings then the speedo is at fault and needs to be replaced, according to the manual. I don't know of another explanation for what you are describing, and none is mentioned in the manual.
Roland

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QUESTION: Hi Roland

Thank you for your quick response.  After holding and releasing the trip odometer reset button it read sof 4.0, then 'error' code (but no number), then 'done'.  The gauges all went through the calibration routine and the speedo did as you describe. 

It seems that the more power the van is drawing the worse the problem is.  If I turn the front and rear fans to high it gets worse. Turn then down or off it gets better.  Could this be an amperage issue?  Perhaps the computer is acting weird due to not enough amps?  Should I check the alternator and if so how?  I'm grabbing for straws. Thanks for your help.

Dave 

ANSWER: Hi Dave,
The word that appears after Sof 4.0 is supposed to be 'end' if there are no error codes. But there is no explanation for why the word 'error' would appear.
On the power question, the cluster gets its voltage from fuse 24 so you could see what that fuse's voltage level looks like. It arrives on pin 6 of the cluster. The digital data arrives on pin 9 but I wouldn't know how that would be impaired if it is. Does the speedo reading also 'shift' when you are in motion at a constant speed and you turn on the fans? About the only circuit item that might be questioned is that the downstream #'cold' side of the fuse 24 socket has a diode to ground whose purpose I am uncertain about, but maybe you would want to compare the resistance to ground on that pin (after removing fuse 24#, reversing the polarity of the leads for comparison of whether it differs in +  as compared to the - polarity reading.
Roland

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QUESTION: Roland,

After I got home yesterday I re-calibrated the instrument cluster and saw that what I originally told you was wrong.  It shows “Sof 4.0”, then “E Code”, then “E   End”.  Does that change anything?  Is “E” a code?  

Thanks again for your help.

Dave

Answer
Happy New Year, Dave!
May I ask for your help?
I need your vote of confidence.
I'm in a close race to be recognized as 'Volunteer of the Month' at Allexperts
Purely symbolic, but it means alot to me.
Please click on "Thank/rate the expert" button below/left
It will take you to a page which asks "Would you like to nominate this expert...?"
Click on the "YES"
That's it.
Thanks for taking a moment to help a fellow Chrysler-owner.

Roland

PS: Do it now, the contest closes at 6pm central time.




Hi Dave,
I don't find that "E code" and/or "E end" response listed in the '02 manual, sorry. The "end"  without the "E" is shown to be expected, and I would expect that were there any codes they would appear after "E code", so absent that, I believe the cluster self-check reveals no codes to be present. So checking the voltage supply to the cluster may be the only other thing to look into.
Roland