Codes P0700, P0720 and P1790, transmission not shifting properly?

Tiny
DOT2DOT
  • MEMBER
  • 2003 DODGE GRAND CARAVAN
  • 3.3L
  • 6 CYL
  • AUTOMATIC
  • 280,000 MILES
I have code errors P0700, P0720 and P1790 on the code reader. When these codes are tripped the van starts lurching forward while my foot is on the brake. While driving, it seems like it's still in 3rd gear and the RPMS are reading between 3000-4000 RPMs. I noticed my transmission fluid level is reading about an inch over the full line. Would this be causing the issue? I already replaced the output sensor.
Tuesday, November 21st, 2023 AT 2:44 PM

7 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 110,176 POSTS
Hi,

The P0700 code is a generic code stored in the powertrain control module (PCM). The PCM receives a message from the transmission control module (TCM) of a problem. That sets the check engine light to turn on and have you further investigate.

The P0720 is related to the output speed sensor. However, it could be a wiring-related issue or an issue with the TCM.

The P1790 is a code that indicates an issue immediately after the transmission shifts. This code could be caused by a fluid-level issue.

That leads me to a question. When you checked the fluid level, was the engine running, at operating temp, and was the van on a level surface? If so, in what condition is the fluid? Is it still a pinkish/red color or is it dirty or have a burnt smell?

Let me know so I have a better idea of which way to direct you.

Take care,

Joe
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Tuesday, November 21st, 2023 AT 9:19 PM
Tiny
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The van was level and fluid was cold when I checked it. There’s a mark level for both warm and cold reading. Fluid is still reddish color, but it does smell a little off. I’m guessing from driving with high RPMs? I’ve been temporarily pulling off the road and erasing the codes so I can make it to my destination while trying to figure this out. Probably not a good idea I suppose but don’t have any other option.
Also have ABS code errors telling me all wheel speeds they have a signal failure.
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Tuesday, November 21st, 2023 AT 9:49 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

It sounds like this is a sensor-related issue. Could you send me the codes that you are getting for the wheel speed sensors? It may help me figure things out or at least point me in the right direction.

As far as the fluid level, ATF expands when it gets hot, so it does sound like it has too much. Do me a favor and check it at operating temperature with the engine running. If it is still approximately an inch overfull, you should drain some of it. The next question is why is it overfull? Has anyone added fluid or checked it recently? There isn't any evidence of engine coolant mixing with it, correct?

Let me know.

Joe
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Wednesday, November 22nd, 2023 AT 8:57 PM
Tiny
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Sorry for the late response. I decided to change the transmission fluid and filter. Also changed both input and output speed sensors. Seemed okay till vehicle warmed up and started having same issues. First with the speedometer being erratic and surging until triggering the check engine light. Again, giving me codes P1790 and P0720. My ABS light has always been on since I’ve owned the vehicle. I’ve been told the previous owner had the wrong size tires on it, but I’ve been driving for over a year without a problem till now. I had a couple other ABS codes, but they disappeared on the last reading.
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Saturday, November 25th, 2023 AT 10:29 PM
Tiny
JACOBANDNICKOLAS
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Hi,

Did you inspect or replace the wheel speed sensors that are indicated? Also, try resetting the cluster to see if that changes anything. I attached the directions below.

Joe

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Sunday, November 26th, 2023 AT 4:35 PM
Tiny
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Hi Joe,

I reset the cluster and no change. I’m currently waiting for my order for the wheel speed sensors. I’ll let you know how things turn out once installed. Thanks again.
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Tuesday, November 28th, 2023 AT 11:42 AM
Tiny
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Hi,

Thanks for the update. I was hoping the reset might help. It never seems to be that simple. LOL

As far as the wheel speed sensors are concerned, here is a link that explains in general how it's done. I don't know if you need it, but thought I would add it. If you have any specific questions, let me know.

https://www.2carpros.com/articles/how-to-replace-an-abs-wheel-speed-sensor

I also attached the manufacturer's directions below. When you remove the original ones, chances are they will be corroded and difficult to remove. Take your time. If you have penetrating fluid, you may want to start spraying them down now, so it has a chance to work.

Make sure you don't pry the sensor on an angle. It will break and then it will be much more difficult to remove. Gently twist it back and forth once it starts to move, then while twisting it, gently pull it outward.

Let me know how things turn out for you.

Take care,

joe

See pics below.
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Tuesday, November 28th, 2023 AT 8:26 PM

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