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P720 - output speed sensor issue

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Old 08-09-2011, 02:24 PM
travisaz travisaz is offline
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Default P720 - output speed sensor issue

Hey guys - first off, this is for my wifes car, a chrysler pacifica, but transmission problems are transmission problems, so thought I would post here.

Syptoms: Speedo reads 20mph in drive or reverse when stopped with foot on brake. Hard 1-2 shift. Took to a shop, they diagnosed as an output speed sensor, replaced.

4months later, same issue. I replaced the sensor myself this time. All was good for 1 mo.

Same symptoms again. I noticed the sensor was magnetic, and had collected quite a bit of metal dust on it (car has 90k). I thought this might be messing up the sensor readings. I extracted 5qt of fluid, replaced it, drove it around 50mi, extracted another 5qt of fluid, dropped pan, replaced filter, cleaned everything up really well, put it all back together.

Still doing the same thing. Was thinking I would clean the sensor one more time, but after that I am at a loss.

Couple other notes:

When I remove/replace the sensor, the car drives normal for the first 5-10 miles.

Wife said she saw the battery light flash twice, and one of the times was right when it started acting up again.

The car also has small and gross evap leak that have escalated to a GASCAP warning on the odo display. Gascap is new, I think something is cracked on the fuel pump in the tank, I guess it is common on these vehicles.

Codes are P0700 and P0720.

Any thoughts appreciated!
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Old 08-09-2011, 07:00 PM
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jasonw jasonw is offline
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Vehicle: 2013 Ram 1500 4X4
Location: Sioux Falls, SD
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I will move this to the non-Dodge section.

Chrysler products act very strangely when batteries are weak. The intermittent battery light makes me thing the battery is weak, which may be contributing to your problem. How old is the battery?
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Old 08-10-2011, 01:36 PM
travisaz travisaz is offline
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Join Date: Aug 2011
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Yea, so not sure how old the battery is, but I was playing around with the car last night, and noticed that the speed sensor would act up based on what accessories were on. I.e if I turned on the lights, AC, or opened a door, the vehicle speed reading in my code scanner would spike.

Started out by cleaning the terminals really well, and checking all fuses/connections at the fuse box. I will have the battery tested today, and maybe throw an extra ground cable on it just to eliminate a bad ground as a possibility. I guess after that I will start troubleshooting individual circuits, but I'm not very solid with electrical systems.

Anyway, just wanted to update incase someone runs into a similar issue.
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