P 0720 code - Diesel Truck Forum - TheDieselGarage.com
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post #1 of 7 (permalink) Old 11-03-2009, 10:43 PM Thread Starter
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P 0720 code

I put a thread labeled "OVERDRIVE SHIFTING PROBLEMS" in here and sure a lot of you guys have looked at it. Sean/SSTOCKTON and MOPAR1973 hope you have your ears on.


My truck has gone crazy today. It didn't want to go down the road for me today. The transmission shifting was all over the place. Lockup was not affected. It was also defueling like crazy. If you read my other thread you will know what i am talking about. I just got home and checked for codes. ECM checked normal. PCU had a code P0720 " Low Output speed sensor malfunction, above 15 MPH". Thats the description in my manual.

The question is, does this mean the speed sensor on top of the rear axle is junk, or needs to be replaced??????????
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post #2 of 7 (permalink) Old 11-04-2009, 10:22 PM Thread Starter
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Does anyone know why this code is popping up and which speed sensor is causing this? Is it the one on the transmission itself or the one on the rear axle?????????????????

Help Please, truck is undriveable!!!!!!!!!!!!!!!!!!!!!
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post #3 of 7 (permalink) Old 11-05-2009, 12:42 AM Thread Starter
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What about metal fuzz covering the speed sensor on the tranny, anyone ever have that problem???????????
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post #4 of 7 (permalink) Old 11-10-2009, 02:54 AM
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I had a simelar problem with speed sensors, but the truck still drove fine. I had to replace the sensor in the rear axle because of a crack in the sensor housing, causing my ABS and BRAKE lights to be on. I also was checking my trans sensor, which as you stated, was covered in metal shavings. Well, those metal shavings ended up being bad, as my trans grenaded shortly after me noticing all that....

My best advice to you though....clean off the trans sensor of shavings and put it back in. If it was a rear speed sensor (the one in the diff) it will usually throw a code specific to the sensor. As for the "overdrive shifting problem" code, I'm not the greatest in the know for auto trans, but I would say it could be a simple solenoid - but like I said, I really don't know too much about these transmissions. Have you taken it anywhere, had it looked at at any local shop to diagnose the problem?

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post #5 of 7 (permalink) Old 11-11-2009, 06:22 PM
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I would definitely check the trans output speed sensor. I've seen a few trucks that have a tendency to eat them. They cost about $25 at Dodge, and I always carry a spare.
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post #6 of 7 (permalink) Old 11-24-2009, 01:09 AM Thread Starter
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Thanks Sean and Jeffybuilt.


It was the speed sensor on the tranny. Had a little bit of metalic coating on the tip. I wiped it off and put it back in and has been fine since. Must have been screwing up the signal. Thanks a lot guys. I love this FORUM.
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post #7 of 7 (permalink) Old 11-24-2009, 03:30 AM
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Glad you got it figured out. Now, the next time someone has a problem like that one, you can chime in with your experience and help someone new...paying it forward is the best thing about the diesel bug.

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