I've got a 93 Accord LX automatic. When you start the car the D4 indicator illuminates regardless of shifter position (the rest of the dear indicator lights function normally when shifter is moved).
If you place the shifter in D3 or D4 the car will go into 4th gear and stay there.
If you place it in 2nd or 1st the trans will shift into 2nd gear and stay there.
I believe the torque converter is also not locking up.
We've replaced the TCU with known good,
Replaced both sets of transmission solenoids,
Replaced main relay
Swapped in known good ECU.
Checked/cleaned grounding points on harness.
Fluid looks/smells fine

I'm running out of ideas...anyone have a suggestion?

 

The D4 lamp staying on like that is like a check-engine-light for the transmission. You can check error codes the same way you check for engine error codes, but it's the D4 lamp that flashes instead (or along with) the CEL.

https://www.hondaaccordforum.com/for...l-codes-35962/

 

Plugged into the diagnostic connector, no blinks, both CEL and D4 stayed on constantly

 

If I remember correctly one of the transmission solinoids is bad, most likely the Transmission Shift Control Solenoid Valve. That's why you can only use two gears. What's weird is that you replaced them and still have a problem. Have you tried checking the transmission control unit (TCU or TCM)?
90-93 Accords have a bad habit of burning out the trans computers. So sometimes you won't get a code. The light will just stay on steady when you jump the connector.
If the light doesn't blink when you jump the connector, then your TCM (transmission control module) might be bad.
To verify this, remove the TCM ( it's located under the rug on the passenger side bolted to the firewall. You will find two modules bolted to one bracket. The TCM is the smaller of the two, on the right.
To remove it, you'll need to remove the 4 bolts securing the bracket. Then, unplug both computer modules, and gently remove the bracket.
Next, unbolt the TCM from the bracket.
Remove the four screws that hold on the cover.
Look at the board carefully. If it is bad, you will find a burnt out resistor and a leaking capacitor.
With the connector pointing down, the bad spot will be in the lower right corner.

 

I had a 2007 Accord it was just doing the same thing as yours. It ended up being the TCC solenoid. Torque converter circuit solenoid. I replace the solenoid and still had the same issue. I checked the wiring to the solenoid and to the connector. Turns out the connector was bad as well as the solenoid. Without testing the connector you would have no way of knowing if power was getting to solenoid or ground was bad by looking at the connector. After testing the connector it was definitely bad. Spliced in a new connector and everything worked perfectly. Moral of the story check the wiring to the solenoids that you replaced and their connectors. They may have been the issue all along

 

He has no 1rst or 3rd gear. If you were correct he would get a P0740 code. which would bring him to the Transmission Lock-Up Control System...And possible causes being; Low transmission fluid level, Dirty transmission fluid, Faulty torque converter clutch solenoid valve, Torque converter clutch solenoid valve harness is open or shorted, Torque converter clutch solenoid valve circuit poor electrical connection...On some Honda vehicles the P0740 code may be set by an overheating torque converter problem which is caused by an insufficient flow to the torque converter release circuit....Description The torque converter clutch solenoid valve is activated, with the gear in D4, by the Transmission Control Module (TCM) in response to signals sent from the vehicle speed and the Engine Control Module (ECM). Lock-up piston operation will then be controlled. When the torque converter clutch solenoid valve is activated, the torque converter lockup clutch will engage creating a 1 to 1 RPM ratio between the transmission input shaft and the rotational speed of the torque converter. Lock-up operation, however, is prohibited when A/T fluid temperature is too low. When the accelerator pedal is depressed (less than 2/8) in lock-up condition, the engine speed should not change abruptly. If there is a big jump in engine speed, there is no lock-up. Here are some video links on this problem....

You Tube

and this one also. . ...

You Tube

However, knowing my car the way I do, I could agree it's a possible wiring problem.

 

The saga continues...swapped the old TCM back into the car this morning and everything was good. Drove it around for a while and it started shifting erraticly. Down to 2 up to 3 then it would behave normally. The indicator will blink but not regularly while driving, kind of like loose connection.

ii was sitting in the car with the key on but not running and I heard what sounded like a relay click and the d4 light went out. Shut the key off and turned back to 2position and everything was normal, then heard another click and d4 light is back on...is there another relay somewhere that I am missing?