Codes P-0722, P-0756, P-0780, and P-1734, transmission will not engage, flashing D light?

2005 HONDA ACCORD
220,000 MILES • 2.4L • 4 CYL • 2WD • AUTOMATIC
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CANNON1349
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This car came to me with a flashing D light and the following engine codes:

P-0722 "Output shaft speed sensor circuit no signal"
P-0756 "Shift solenoid B performance or stuck off"
P-0780 "Shift malfunction"
P-1734 "Problem in System - Shift solenoid valves B or C stuck off / Shift valves B or C stuck"

It came with the input and output shaft speed sensors replaced on the outside of the case, as well as the dual linear solenoids on the case, and solenoids B and C inside the trans. The fluid is new so I can't see any kind of metal, but I'm still thinking that this transmission is toast. Unless someone thinks it may be a computer issue, I would think replacing the "stuck" valves would improve something, but the car doesn't even move.
Feb 7, 2023 at 7:17 PM
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CANNON1349
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Just an update, looking at the Honda diagram of solenoids, looks like they replaced solenoids "E" (black connector) and "C" (brown connector). Should I go ahead and replace the "B" (brown connector) solenoid?
Feb 8, 2023 at 8:22 AM
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JACOBANDNICKOLAS
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Hi,

My first thought when reading the post was the speed sensor until I realized the was no engagement.

That is the only other solenoid left from the diagnostic codes you have. You can try to replace it, but there could be a wiring issue or a module issue.

Let me know your thoughts. Also, let me know if I can help in any way.,

Take care,

Joe
Feb 8, 2023 at 3:13 PM
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CANNON1349
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From all the tech tips I can read, it looks like some techs are able to drive the car to test the sensor functionality. But this car has no engagement. Even so, the most common repairs look like the solenoids or replace the trans, especially if P1734 is showing. The solenoid will cost around $60.00 and a junkyard trans around $350.

I'm curious if there is a circuit going from the solenoid harness to the output shaft sensor connector. And I remember there is a Honda test for these solenoids, you jump a wire from the positive terminal to terminal #2 for solenoid B, but I am unsure of the terminal # for solenoid C.
Feb 8, 2023 at 5:57 PM
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JACOBANDNICKOLAS
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Hi,

I attached the diagnostics related to solenoids B and C. Take a look through them and let me know if they help.

Take care,

joe

See pics below.
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Feb 9, 2023 at 5:17 PM
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CANNON1349
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Thanks Joe, but I am referring to the shift solenoids inside the transmission. There is an 8-pin connector and allegedly you can jump the positive terminal to the harness and engage them individually and hear a click.

If there is no click with a new solenoid. We can confirm there is an electrical issue? And if it does click but no engagement with the trans, we could condemn the transmission?
Feb 9, 2023 at 5:24 PM
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JACOBANDNICKOLAS
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Hi,

I just went through every schematic I have and cannot find a connector view. I can tell you that the power supply to shift solenoid C is provided via the PCM and the wire you are looking for at the connector is green.

If possible, locate that wire and determine the pin it connects to. If you apply voltage, you should hear the solenoid engage.

Sorry about the pinout. I have no idea why it isn't listed.

Let me know if this helps.

Joe

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Feb 9, 2023 at 6:47 PM
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CANNON1349
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I replaced solenoid B and so far, the codes have shrunk down to just P0780 and P1734. The car still does not engage, but the D light stopped flashing. Only sometimes it will jerk to feel like it engages in reverse. What are your ideas for the next step?
Feb 15, 2023 at 7:20 PM
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JACOBANDNICKOLAS
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Hi,

The P0780 code is a general DTC that is stored at a time the P1734 is set. So, we need to focus on P1734.

I attached the diagnostics below. It will indicate checking shift solenoids B and C. It will also request you drive the vehicle (which isn't possible).

Allow the engine to reach operating temperature and drain the transmission fluid as described checking for evidence of internal damage.

Let me know what you find.

Joe

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Feb 16, 2023 at 4:49 PM
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CANNON1349
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My other concern is, the testing of shift solenoids is in regard to the clutch pressure solenoids B and C on the case? Or the internal shift solenoids B and C inside the transmission?
Feb 16, 2023 at 4:55 PM
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JACOBANDNICKOLAS
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The shift solenoid valves are external. The shift solenoids are internal.

The shift solenoid valves are responsible for line pressure. Since you have no response when shifting, that would be my first suspect.

At this point, you may be better off checking the line pressure to see if it is low. I say that because of no gear engagement.

I attached the directions below for testing line pressure. Take a look through them and let me know if you are comfortable performing them.

Take care,

Joe

See pics below.
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Feb 16, 2023 at 7:25 PM
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CANNON1349
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I am comfortable doing it, but I don't have equipment to check the line pressure. I thought about removing the in-line filter on top of the transmission and seeing if that gained some pressure. Also, I think about removing the B and C solenoid that the previous tech replaced and checking if there's something in the screens.
Feb 17, 2023 at 7:32 AM
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JACOBANDNICKOLAS
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Hi,

If you perform the line pressure testing, it may prevent you from taking things apart again. I realize most people don't own the gauges needed, but often times a parts store will have and lend one to you. It's just a thought.

On the other hand, your suggestions are certainly relevant and are a good idea.

Let me know what you decide. If I can help in any way, I'll give it my best shot. LOL

Take care,

Joe
Feb 17, 2023 at 8:02 PM
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CANNON1349
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Hi,

Well, I still don't have a way to test pressure in the trans, and much to my dismay the codes came back, P0722, P0780, P1734, P0756. The only difference is that now after replacing solenoids B and C, as well as the solenoid pack B and C on the case, the trans will shift into reverse sometimes. Occasionally it will pull in Drive. Looks like after the trans warms up it is less likely to engage, and also there is a high pitch whine coming from the trans.
Mar 6, 2023 at 4:28 PM
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JACOBANDNICKOLAS
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Hi,

The noise has me concerned. It could be the front pump, the torque converter, and a few other things.

Is it possible for you to record and upload it for me to hear?

Let me know.

Joe
Mar 6, 2023 at 7:08 PM