Thanks TexasHonda and PAHonda for you input...

For clarification, the original code was a solid D4 with no check engine. Plugged in the SC and got MIL code 41(O2 sensor circuit problem) on the check engine light and no code on D4. Pulled back-up fuse to clear codes and both the check engine and D4 lights turned off were now off.

Next day car acted up w/o any codes reappearing. Code 41 has not reappeared since.

Friday evening when I got home, both son and I drove around for at least ½ hour. No lights no codes, transmission behaving absolutely normal.

So I let him drive to work over the weekend and it acted up once. He explained it feels like it’s not downshifting to 1st gear when coming to a red light. To get going he manually goes in first gear by moving the shift level to D1. Then to D2 and eventually back to D3/ D4 once he’s up to speed. He can correct the situation by removing the back-up fuse for 10 seconds or more. There was no check engine light. D4 was on steady. Put in the service connector and he says he got one D4 blink, but no repeat of the one blink??

I was hoping for a better code output, one that is more definitive, I’m going to drive it for work for a day or two and see what I come up with.

 

A one blink D4 indicator light may possibly be related to the lock-up control solenoid valve A, wiring, etc. Check the electrical connector to see if it is clean and tight.

 

Read my post "Transmission Toast?" in this forum.

I know they are different years but I do remember the mechanic saying "if this was an early '90s accord I would say computer all day long."

I am leaning towards computer problem, but be careful driving it as you could damage the transmission accelerating in third or fourth gear from a stop.

 

Drove the car yesterday to work and back w/o issue.

I read about the issues with the early TCM, namely the capacitors leaking corrosive material onto the PC board and causing transmission shifting issues. I believe this is the most likely failure based on my son’s observation about feeling like it’s getting stuck in 4th gear when coming to a stop.

Is there a way to confirm the failure as the TCM? Could I damage the transmission driving it this way? Lastly, has anyone had experience with secondary source of reman/reconditioned TCM’s?

 

From TSB 90-039

Symptoms: S light is on and trans is stuck in 3rd or 4th gear. The LED on the TCM stays lit and will not blink an error code. The interlock control unit (under the dashboard above the fuse box) buzzes or clicks.

Vehicles Affected: 4dr up to VIN 1HGCB7...LA121350
4dr up to VIN JHMCB7...LC104599

Diagnosis: Any of following confirm problem.
1) Depress the brake pedal. The interlock control unit stops buzzing or clicking
2) Reset the A/T Control Unit by removing fuse 24 in the underhood fuse box, then tet drive the car. The S light remains off and transmission shifts normally.
3)Removing fuse 24 does not clear the A/T control unit.

Corrective Action: Replace the A/T Control Unit (TCM).
Parts Information:
Japan Built EX: P/N 28100-PX4-932
H/C 3523933

Japan Built Lx & DX: P/N 28100-PX4-922
H/C 3520269

US-built EX: P/N 28100-PX0-932
H/C 3521796

US-built LX & DX: P/N 28100-PX0-922
H/C 3521788

good luck

 

Thank you TexasHonda, if it wasn't for you all, I would have had the transmission replaced and not fixed the problem.

This morning I removed the TCM for inspection. Didn't expect to find anything, yet I think I found the problem... R41 resistor is burned or overheated. See below.

 

See following thread about R42 and other possible component problems:

https://www.hondaaccordforum.com/for...th-only-30793/

Some google searching may find further guidance on what to replace.

Youtube video "another Transmission Control Unit repair" may be helpful.

good luck

 

Yes, I came across excellent information about this problem at another website. I’ve attached it here for the benefit of others who may have a similar problem.

http://techauto.awardspace.com/transmission.html

In the mean time I brought the TCM to a good friend who is an Electrical Engineering technician and he is replacing suspect resistor and capacitors. I hope to have it back today. I will post after the TCM has been installed and the car road tested.

 

Got the TCM back and installed in the car. Went for a test drive, shifts seem normal. I let my son drive, since he uses it for school, he said he could tell very quickly the shifting was better. So we’ll monitor it and make sure no issues pop up.

Many thanks to all who contributed to identifying the issue.

 

It’s been 6 weeks since the circuit board resistor and capacitor components were replaced. Transmission operation has been excellent until yesterday, a new symptom has appeared.

The “D4” light cycles on and off with the clicking sound of the brake interlock switch. Step on the brake and the cycling sound stops, but the D4 light still flashes erratically. When driving at a steady speed I can feel the transmission shifting back and forth between gear. Coming to a stop it will sometimes be stuck in 3rd or 4th gear. No issues with shifting out of “Park”.

With the SC plugged in I get no codes. Removing the back-up fuse to reset computer helps for only a short time, until symptom returns.

What do you guys think, is this a faulty interlock switch, or do I need to replace TCM?