I just replaced the transmission control unit on my gf's 1990 Honda Accord and now the car won't start!

Prior to the replacement, the car was running fine with the exception of the green "S" light would come on from time to time and the car would no longer accelerate normally (as if stuck in 1st gear). After seeking support, some suggested it was probably the TCU. So I went purchased a new "used" one (which the seller said was working) to replace it.

I took out our old one and replaced it with the new one and now our car won't start.

I even put back the old one (just plugged it in, didn't put it in the bracket) and the car won't start with the old one either.

So now are car won't start!

Any ideas?

By the way, during the process I unplugged the ECU as well because I was replacing the heat blower motor and needed to get the whole bracket out of the way. Could that be the problem?

 

Yes, it may be poor connections on the ECU. Check, check and triple check that the connections are firmly in place and that the unit is securely bolted to the body. Did you disconnect the battery prior to working on it?

 

I'm prertty certian the connections are firm. I heard them all click into place.

I did not disconnect the battery =/ Didn't know it was necessary. What does that effect?

Also I hadn't fully bolted it in yet because I didn't want to undo it all in case the new (used) one didn't work as promised.

Extra notes... When attempting to start the car, it turns over, but just won't start and the green "s" blinks continually.

Also, I tried removing the fuse to the ECU, let it sit for 15 min (read this somewhere else) and that didn't work either.

 

Anyone have any ideas? Really need help

 

1. When you try to start the car, does the Check Engine Light:

(a) come on and go off after a few seconds or
(b) does it not come on at all or
(c) stays on?

2. In addition, since the "S" light is blinking, jump the two terminals of the Service Check Connector (located behind passenger kick panel area), then turn on the ignition switch and observe the blinking "S" light to obtain the trouble code(s).

If the TCU has an LED on it, you do not have to jump the Service Check Connector to obtain the trouble code(s). You would just observe the blinking LED on the TCU.

Problem codes 1 through 9 are indicated by individual short blinks, Problem codes 10 through 1 5 are indicated by a series of long and short blinks. One long blink equals 10 short blinks. Add the long and short blinks together to determine the problem code.

 

Thanks fir your response! Will check the engine light in the morning and get back to you since I don't rememner and am currently not at the car.

In the meantime, what does "jump the service connector" mean?

 

See this thread:

https://www.hondaaccordforum.com/for...al-pics-49074/

A small wire or paper clip to jump the connector may also work.

 

OK. So I get a chance to check what you asked. When I start the car, the Check Engine Light stays on. I've recorded a short video to show what the car is doing. You can also hear it trying to start.

 

Something is up......yes, that is why you have a question. The tach is not moving at all so there is no ignition signal.

Is it possible the 10amp ECU fuse in the underhood fuse box is blown?

 

The fuse looks good.

Interesting you mentioned the something ignition related. A friend thought it could be the ignition coil, but I thought that would be a big coincidence that it would go out into the time I replaced the TCU becuasr the car was starting fine before that.

This *#$%&! car My gf accidentally bought it at auction (yes... actually bid by mistake) and we've been stuck ever since. But.. been fun fixing some stuff on it