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Vehicle RPMs do not rise above 3,200, codes P1775 and P2120

Tiny
MALLYBOY
  • MEMBER
  • 2004 DODGE CARAVAN
  • 3.3L
  • V6
  • 2WD
  • AUTOMATIC
  • 95,000 MILES
This vehicle does not raise above 3,200RPMs at wide open throttle. When I diagnosed the instrument cluster and transmission using garage pro app and obdlink scanner, it recorded code p2120 only without description and on transmission it recorded p1775.
I used Autel scanner Maxispro to diagnose it again and it recorded description without fault code: "improper power down detected".
And while accelerating the vehicle, if you throttle on second gear to move faster and shift into third gear, it will begin to drag and will not shift until you release pedal and depress it slightly before it shifts upward gear
At this point I don't know how to analyze and solve the problem.
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Saturday, January 8th, 2022 AT 3:52 AM

8 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
This sounds like a fluid issue in the transmission or possibly a greater issue due to the fluid being low.

So, the first thing to do is check the fluid level and see what the condition is.

https://www.2carpros.com/articles/how-to-check-and-add-transmission-fluid

What I suspect is happening is the fluid is low or in poor condition and it has caused damage to the torque converter and possibly more inside the unit.

If this is the case, we may need to drop the pan and inspect for metal inside the unit.

I attached the material below on these codes and how to check the fluid.

Let us know what you find, and we can go from there.

Thanks
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Saturday, January 8th, 2022 AT 4:25 PM
Tiny
MALLYBOY
  • MEMBER
  • 309 POSTS
All checks okay. Again, if the vehicle is on 1st gear and you throttle-down to shift to 2nd at wide open throttle, it will begin to drag until you release the throttle pedal and depress slightly it will shift to 2nd gear. This problem is not between the throttle body, instrument cluster and valve body since it recorded fault code:P2120 on instrument cluster?
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Sunday, January 9th, 2022 AT 1:12 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Did you go through the testing for the P1775? I understand if the fluid checks out okay, but this still sounds like this is where the issue is.

It may not be the fluid itself but that is going to give us indicators as to what the issue is.

Have you dropped the pan to look for metal?

Basically, this code is telling you that the torque converter switch is stuck engaged which means the converter is locked when it should not be.

This is going to cause the engine to bog way down and not shift. Then when you get off the throttle and back on slightly it allows the TCC to release and it shifts.

I am pretty confident that you have internal transmission issues and if it were me, I would be dropping the pan to see what is in it and then most likely rebuilding the unit.
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Monday, January 10th, 2022 AT 8:36 AM
Tiny
MALLYBOY
  • MEMBER
  • 309 POSTS
This is going to cause the engine to bog way down and not shift. Then when you get off the throttle and back on slightly it allows the TCC to release and it shifts.
1. Where is the location of the torque converter switch?
2. This is a valve-body problem because if you engage reverse, you will feel hard-shift but if you engage DRIVE, you will not feel anything but smooth engagement.
I have removed the pan but didn't see anything
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Monday, January 10th, 2022 AT 1:12 PM
Tiny
KASEKENNY
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Okay. This does sound like a converter issue, so the TCC switch is part of the valve body. If the fluid is in good condition and you have no metal in the pan, then you should be fine replacing or just rebuilding the valve body.

They are pretty easy on this vehicle using the exploded view below.
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Wednesday, January 12th, 2022 AT 3:55 PM
Tiny
MALLYBOY
  • MEMBER
  • 309 POSTS
This does sound like a converter issue. Do I need to replace the torque converter because presently there is a whining noise on the transmission? And if you first engage the drive or reverse it will move and shortly it stops and you begin to hear the noise on the transmission, I have check the pump by removing cooler hose and crank the vehicle and it pumps fine but I have not check fluid filter to see if it was block starving the transmission with oil.
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Friday, June 3rd, 2022 AT 10:33 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
The pump on these vehicles is noisy so get a recording of the pump. It could be a pump issue but if you are getting P1775, then we need to go through that testing because we are just guessing at it otherwise.

I attached the testing above so let's start with a recording of the pump and then run through that testing.
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Saturday, June 4th, 2022 AT 2:00 PM
Tiny
MALLYBOY
  • MEMBER
  • 309 POSTS
Hello!
Thank you so far,
I replaced the transmission filter and the winning noise stopped. Then transmission became fine. Therefore, for the vehicle bogging down or jerking when you depress the vehicle at wide open throttle was caused by ECM because it was recording P0201: Injector Cylinder1 circuit open. Then I replaced ECM and program it and crank the vehicle, then I road-test and while on test-drive, I depress the throttle pedal way fully down and the vehicle kick down electronically and drive at faster speed before shifting to 2nd, 3rd and 4th gear at a greater speed without bogging down or jerking again, so problem solved not even transmission issue.
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Friday, August 25th, 2023 AT 7:16 PM

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