1993 Honda Accord
VIN: 1HGCB9856PA004376
Honda TCU 28100-px0-a32
When I bought the vehicle there were no fault conditions present.
I made many repairs to the vehicle to ensure reliability.
After I had the A/C converted to R134 two fault conditions appeared on the TCU and one fault condition appeared on the ECU.
The ECU fault condition (6) was remedied with a new coolant temperature sensor.

The following is a listing of actions to remedy the TCU fault condition.

Problem: Shifter D4 light flashes indicating a transmission circuit fault.
Codes to flash translation:
2 flashes = Lock-up solenoid 'B' circuit open or shorted.
7 flashes = Shift Solenoid 'A' circuit open or shorted.


Repair attempts to date:
1. Unplug and clean connectors at point closest to solenoid.
Flashing code stopped but returned after one day.
2. Remove solenoid pack, clean exterior, test resistance of each solenoid in pack, both have continuity to ground. Test each solenoid with 12VDC, each opens and closes with solid activation sound. Clean/flush each electrically opened solenoid with brake cleaner, clean screen gasket, Reassemble and test.
No change in fault flash condition
3. Test continuity of wiring from TCU to disconnect terminal closed to solenoid pack
Both the Gn/bk wire to the lock-up solenoid and the Y wire to the shift solenoid A have continuity to ground. No change in fault flash condition
4. Test voltage while running at the disconnect terminal closed to solenoid pack.
Lock up solenoid: 13.0 VDC
Shift solenoid A: 11.3 VDC
5. Replace TCU with “believed to be good” unit from a 1993 accord with 57K miles. TCU number: 28100-px4-721
No change in fault flash condition
6. Replace original TCU circuit board components with new components:
Capacitors: #3, 33uf / #5, 1fu, / #27, 4.7uf. / #28 220uf, / #32, 330uf
Resistors: R41, R 42
Inspection reveals that capacitor has green electrolytic compound present at base of capacitor. All other components look good. Capacitor #28 220uf 35V came apart in my hands while installing. Seller provided another cap.
Reinstall TCU and test operation.
No change in fault flash condition
7. Test solenoid resistance to ground from TCU
Lock up solenoid: 14.5 ohms to ground
Shift solenoid A: 14.5 ohms to ground
No continuity between wires for solenoids
8. Replace solenoid pack with reconditioned solenoid pack purchased on Ebay.
No change in fault flash condition
9. Replace capacitor #28 220uf with new unit.
No change in fault flash condition
10. Purchase and re-replace all capacitors listed above with high quality components using the logic that if one capacitor failed, the others could be poor quality as well
No change in fault condition.

At this point I am fully open to discussion / suggestions and really want your input.

 

Welcome, but the post is too complex for me - don't know what problem you are seeking input on.

 

I assume it's the D4 lamp codes 2 & 7 haven't been fixed yet?

 

You are correct sir, I haven't found the time to pursue any further.
My goal was to look into it further this weekend but, that didn't happen.
I did read the post here asking if the person's cruise control still worked with these codes presented and said it may be a speed sensor as it could set these codes...?
I went to start the car to find a dead battery. The car is on the charger now.
I'll see if the car starts and the cruise works, perhaps Tuesday morning if time permits.

 

The speed sensor won't set these codes.

Your test 7 doesn't necessarily rule out the wiring from the TCU to the solenoids. Unplug the TCU and keep the solenoids plugged in. Apply 12V to the wire to each solenoid and verify that the solenoid opens or closes.

 

Also how about checking continuity from the wires to ground while the solenoids are unplugged? It would be a strange coincidence for the resistance to ground being similar to the correct resistance for the solenoids, but also good to rule out problems with the wires.

 

Jim Blake:
Did that, solenoids function as intended.

 

resistance to ground with solenoids installed as tested as listed, 14.5 ohms.
resistance to ground with solenoids unplugged was tested and found to be open.
resistance between each circuit of the solenoid pack was tested and found to be open.

 

Thanks PAHonda, I'll double check and post.