ptownbro

We have a 1990 Honda Accord DX that was starting and running fine, but had some transmission issues. After some research and forum help, we figured the transmission issues were due to a bad TCU so I replaced it. Now the car won't start at all (it cranks/turns over, but won't start).

After trying a number of things, I noticed a red light flashing on the back of the TCU and need help deciphering them. Here are the patterns:

Pattern #1: solid-1-2-3-7-8 (this occurs right after turning car on)
Pattern #2: 1-2-3-7-8
Pattern #3: long-4-1-2-3-7-8
Pattern #4: long-4-1-2-3-7-8
Pattern #5: long-4-1-2-3-7-8

Any ideas?


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Some extra information:

When replacing the TCU I also unplugged the ECU (I was replacing heater blower and it was in the way) and had the battery plugged in while doing so. Thinking maybe the ECU is preventing the car from starting?

At one point the car actually started, but never again after that.

Things I've tried:

1. Removed the ECU fuse several times
2. Completely disconnected the battery (for more than 24 hrs)
3. Tried replacing the ignition coil.
4. Checked all fuses
5. Made sure both the TCU and ECU are connected properly.

MAD_MIKE

I don't recall my TCU's having this light. Does your car not have a D4 or S lamp on the dash? Do they not illuminate when turning the vehicle ignition to II(ON) initially.

What engine size, induction type, and region is your vehicle from?

Pattern #2 makes sense, but the rest seem out of order. Normally codes are shown in numerical order
4 or 14 should not be before the rest.

1/2 and 7/8 are for the lockup and shift solenoid pairs respectively. Highly unlikely they are all bad, verify connections and wire harness is not damaged.

3 would be for TPS, which may cause a no start issue if the circuit is open.

4 would be for VSS, car should still start without it.
14 would be for the FAS wire, a communication wire between ECU and TCU.

thefew

Here are the TCU codes:

1-Lock-up solenoid 'A' circuit open or shorted.
2-Lock-up solenoid 'B' circuit open or shorted.
3-Throttle Position Sensor circuit open or shorted.
4-Vehicle Speed Sensor open or shorted - No signal from speedometer.
5-Shift Lever Position Switch circuit shorted.
6-Shift Lever Position Switch circuit open.
7-Shift Solenoid 'A' circuit open or shorted.
8-Shift Solenoid 'B' circuit open or shorted.
9-Counter shaft or transmission speed pulse generator open or shorted.
10-Coolant Temperature Sensor open or shorted.
11-Engine RPM (Ignition coil signal) open or shorted.
12-(No code 12 used)
13-Main shaft speed pulse generator open or shorted.
14-Linear (line pressure control) solenoid open or shorted.
15-Kick down switch circuit shorted.

MAD_MIKE

These are not applicable to the 90-97 H4A transmissions found in 90-97 Accords, 92-96 Prelude, and 95-97 F22 Odyssey.

Tech Auto has those listed, but I do not know where they come from.

These are the codes found in the Honda FSM.

'90-'97 model OBD I TCU codes(Using two wire blue connector.)
'H4A' transmission. (known as AOYA, BOYA, MPJA, MP1A, etc etc.)

1. Solenoid Valve A Lockup Control
2. Solenoid Valve B Lockup Control
3. TPS*D4 may or may not light*
4. VSS
5. Console Switch
6. Console Switch *D4 does not light*
7. Solenoid Valve A Shift Control
8. Solenoid Valve B Shift Control
9. NC sensor
10. Thermo sensor
11. Ignition Coil *D4 does not light*
12. Not Used
13. Non Specific, Possibly BARO sensor.
14. FAS-wire *D4 does not light*
15. NM sensor *D4 does not light*

thefew

Thanks for catching that MAD_MIKE. Sorry about the bum scoop.

ptownbro

Sorry for the delayed response. I didn't realize I was getting responses. Anyway, I was able to get the car fixed.

When I originally was working on this I only checked the fuse box that was under the hood on the passenger side. There are ECU fuses there which I removed and replaced thinking that would reset the ECU.

However, I stumbled on the other fuse box which is inside the car under/near the steering wheel. There was another ECU fuse there as well!! When I pulled that one and replaced it.... the car started!

I guess that's all it was. The ECU need to be reset by pulling all the associated fuses both under the hood and inside the car.

Thanks everyone for your help

MAD_MIKE

Did you test the old fuse? A fuse may look 'good' but is in fact blown.
Always test fuses.

ptownbro

I did not, but the car has been running great since that (over a month now), so I believe the problem has been solved. I'll keep that in mind though for the future. Thanks!