ERE Auto Mechanic

[HSpencer]

I have a great 1992 Honda Accord, except for the transmission control Computer -"Electronic Control Module"-or (ECM).

THe ECM collects data on each shift of the transmission as the car is operated. At some point, this data is dumped out of the ECM's memory, and the process starts over. Mine will not dump the data, and the transmission will not then shift into 3d and 4th gears.

At the dealer, I notice the technician using an electronic tool device to "clear the computer". When I ask, he says "you can do the same thing by disconnecting the negative battery cable".

Brain lightbulbs come on.

The next time the problem occurs, I disconnect the negative cable and in 30 minutes the computer clears, and the car shifts fine. This lasts about two weeks of everyday driving until the computer fills up with data again.
To Repair:
Consumer Method: Pay the dealer $750.00 for a new ECM plus $175.00 labor to install and program it.
ERE Method: When the problem occurs, disconnect the negative cable and wait 30 minutes, reattach and continue to march.
If the car was a needed daily driver I might get the new part. For now, it is a cheap driver, and extra ride if needed only.

In time I plan a restoration of the car to like new condition.
I will for now forgo the +/- $1000.00 to repair it. I have a nice battery cable wrench!!!!

[jacob]

You could also install a battery disconnect switch (RV store), which would also work as an antitheft device. Not sure it's mission safe though---it's normally done on the "house batteries".

[George the original one]

For most modern cars (e.g. post 1990), disconnecting and reconnecting the battery is now the first diagnostic step. If that fixes the problem for more than a week, then there's no need for a visit to the mechanic.

[jacob]

"Tech support. Have you tried switching it off and on?"

[HSpencer]

I have been playing with this for a while now. I have even had the ECM out of the car once. It is not too complex taking it out, as you lift the passenger side carpet, take out a metal panel and there it is. Two more screws, a disconnect, and its out in your hands. I looked on the internet, and there is a place that sells you one in exchange for your old one. In this case, the exchange price is $350.00. Still a lot of money for a 90 day warranty on it. They claim it's a plug and play, but the dealer told me a new one would need programing. The one from the internet is a reconditioned one.

If you disconnect the negative battery cable, that cuts all power to the thing and that is the secret to making it dump the stored data. It must be like a reboot. When I had the ECM out of the car, when I put it back in, the car shifted normally up until the ECM filled up again with data.

[KevinW]

Another idea: wire a toggle switch in series with the power supply to the ECM. Then you can reboot the ECM without disrupting anything else. Toggle switches are cheap and you can often salvage them from discarded electronics. This will only be feasible if you can isolate that wire on the wiring harness.
Nine times out of ten when a mechanic charges you for diagnostics, all they do is plug in a more expensive version of this thing

http://www.amazon.com/Actron-CP9125-Poc ... 05&sr=1-14

and read the trouble codes out of the engine ECM. One advantage to all these electronics is that cars can do a good job of diagnosing themselves when the problem has something to do with the onboard sensors.

[HSpencer]

@ KevinW
I found a lot of information on the internet concerning this problem with the 92 Accords. This is not an uncommon fault of the model year. I might possibly wire a switch into the power wire of the ECM. I think there is schematic on the lid of the ECM housing which might pin down the power wire that comes from ? to the ECM. Honda is a reliable car, but you have to think a little differently when working on one. The way they are put together sometimes defies reason compared to American made ones.