Transmission problem, codes 0700, 0720 and 0731

Tiny
BRUCE JEAN
  • MEMBER
  • 2001 DODGE CARAVAN
  • 3.3L
  • V6
  • AUTOMATIC
  • 245,000 MILES
Codes 0700, 0720, and 0731. Trans hesitates going into gear then bangs, speedometer reads 20 in gear with foot on brake, then bounces all over, then goes to 0 in park. Changed input, and out put speed sensors, and still does the same thing.
Saturday, September 1st, 2018 AT 6:57 AM

11 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good morning.

How long since you had the oil/filter changed in the transmission? If it has been a while, I would start there as a clogged filter will cause many issues.

Roy

720

P0720 - OUTPUT SPEED SENSOR ERROR

When Monitored and Set Condition:
P0720 - OUTPUT SPEED SENSOR ERROR

When Monitored: The transmission gear ratio is monitored continuously while the transmission is in gear.

Set Condition: If there is an excessive change in output RPM in any gear.

Possible Causes:

Intermittent wiring and connectors

Output speed sensor signal circuit open
Speed sensor ground circuit open
Putput speed sensor signal circuit short to ground
Putput speed sensor signal circuit short to voltage
Speed sensor ground circuit short to voltage
Output speed sensor error
TCM - output speed sensor

731

P0731 - GEAR RATIO ERROR IN 1ST

When Monitored and Set Condition:
P0731 - GEAR RATIO ERROR IN 1ST

When Monitored: The Transmission Gear Ratio is monitored continuously while the Transmission is in gear.

Set Condition: If the ratio of the input RPM to the output RPM does not match the current Gear Ratio.

Possible Causes:
Intermittent gear ratio errors
Transmission - internal

https://www.2carpros.com/articles/how-to-service-an-automatic-transmission

https://www.2carpros.com/articles/automatic-transmission-problems
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Saturday, September 1st, 2018 AT 7:21 AM
Tiny
BRUCE JEAN
  • MEMBER
  • 7 POSTS
Thanks Roy. I will try a filter change. Do you know how to check for open circuit, low voltage, open ground? I have a fluke tester. I appreciate your help, Bruce.
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Sunday, September 2nd, 2018 AT 6:31 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Sure, those checks are fairly easy.

Try the filter change first before we go there.

Roy

https://www.2carpros.com/articles/how-to-use-a-voltmeter
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Sunday, September 2nd, 2018 AT 6:39 AM
Tiny
BRUCE JEAN
  • MEMBER
  • 7 POSTS
Okay Roy, I will get back to you later today.
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Sunday, September 2nd, 2018 AT 10:44 AM
Tiny
ASEMASTER6371
  • MECHANIC
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Sounds like a plan.

Roy
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Sunday, September 2nd, 2018 AT 10:59 AM
Tiny
BRUCE JEAN
  • MEMBER
  • 7 POSTS
Changed fluid, filter, still the same. Foot on brake, put in gear, speedo goes up to twenty mph, ane bounces around, check engine light comes on, 0700, 0720, 0731. Had daughter put in gear and watch speedometer while I wiggled all wires and plug ins to speed sensors. Speedometer never changed.
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Sunday, September 2nd, 2018 AT 6:46 PM
Tiny
ASEMASTER6371
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Okay, you have done all you can do externally.

The only thing left is an internal failure in the transmission itself. As the one code referred to, the gear ratio is slipping internally. That indicates a failure of the clutches, steels or seal issues.

It will have to be removed and most likely rebuilt.

Roy
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Monday, September 3rd, 2018 AT 4:56 AM
Tiny
BRUCE JEAN
  • MEMBER
  • 7 POSTS
What about a TMC, is that a possibility?
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Monday, September 3rd, 2018 AT 11:01 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
I believe you mean the TCM which is the module.

731 is the key here with slipping going on inside the transmission that is mechanical, not electrical. The TCM does not control mechanical functions just electronic.

The simple answer is no. It would be a waste of money in my opinion.

Roy
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Monday, September 3rd, 2018 AT 2:35 PM
Tiny
BRUCE JEAN
  • MEMBER
  • 7 POSTS
Okay, thanks for your help Roy.
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Tuesday, September 4th, 2018 AT 4:36 AM
Tiny
ASEMASTER6371
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You are welcome.

Glad to help.

Roy
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Tuesday, September 4th, 2018 AT 1:25 PM

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