93 Accord ECU Question for Techs. 93 Accord not starting.

Hi,

I have a 93 Accord EX that won't start. Please read all.

I have been having intermittent transmission shift problems for a
couple weeks now but they would dissappear for a day or two after I
disconnect the neg. battery cable to reset the Transmission ECU. I
suspected the problem to be the Transmission ECU after checking the
solenoids and sensors. I also tried getting the diagnostic code but my
check engine light would just stay on and not give me any codes.
Anyway...

Last week I got in the Accord and it would not start. It turned over
strong but would not fire. I thought that the Transmission ECU finally
went and that it would not allow the engine to start. Well here are my
findings...

I disconnected the battery, pulled the Trany ECU and also the Engine
ECU. I first opened up the Trany ECU, everything looked normal,
nothing burnt or discolored. Then I opened up the Engine ECU and there
it was, one of the transistors was totally fried. I was able to get
the numbers off of it (c2655) to get a replacement and the resistors
around it checked okay. I figured I'd give it a shot so I ordered a
couple of new transistors.

Today I installed the transistor, checked all the fuses and put
everything back together BUT the darn thing still won't start. Took
the ECU back out checked the transistor, checked my solder joints
again and checked a few other components. Everything that I could
check was okay on the board. Obviously something else is fried
probably a chip, I just can't see it.

Now to my questions.

Is this a frequent problem? (the transistor or ECU frying)

Could the Engine ECU have caused the intermittent transmission
problems all along?

Do you think that the transmission problem/Trany ECY could have caused
the transistor in the Engine ECU to fry? (The two ECU's share some
information/wiring)

What do you think could have caused the Engine ECU to fry?

Should I take the chance and get a new Engine ECU at the junk yard or
off the net and hope that it works?

Do you think that a new ECU will also get fried?

What do you suggest?

Thanks,
Tom

 

I browse this group often and found a couple fried transistors in ECUs. I
remember one fried TCU. (ECU is for engine and TCU is for transmission.)

I doubt it. ECU can send speed, rpm signals, and a few others.
But the ECU is innocent until proven guilty.

I think it's a wiring short or a component short.

Yes, but first locate why it shorted. Yes, trace
every single wire related to the fried transistor.

Yes. ECU are pretty reliable stuff. If operated
without connecting to various components
outside itself, it would last forever. AFIK

Ask yourself why the transistor blew and how it
could be avoided. A shorted solenoid can blow
a transistor. But it's usually not the solenoid, it
could be in the wiring. I've driven 93 Civic with
TCU and no shorts. I drive a 93 Accord and it's
a nightmare of shifting, shorting problems, no starts,
no spark, all relating to the wire harness. It's now in
top condition. The whole harness was evacuated and
reassembled. This is a repair trick that works most of the time.

The TCU check light stays on means it's dead
or shorted somewhere, harness or internal.

When we replace transistors we normally check it's
functionality by operating it. Either with a logic pulser
or operating the car. When it activates it makes a complete
circuit to ground. You trace where ever this circuit takes,
hooking a 2-Ohm 1/4 watt resistor in series and feel the
temperature of the resistor is a good trick. And I doubt
the transistor's base driver is dead, you check this by
operating the ECU. Reverse engineering circuits is tuff,
unless a schematic is available, I doubt it. You should
just make sure the harness is good and just swap in a new ECU.

Testing harness is something you can do with a service
manual. The manual didn't leave any wiring out during
my diagnostic attempts.
Waltson