Hello group,
This vehicle 1991 Honda Accord EX; came in with intermittent 3rd gear. Another shop removed D4/S bulb after transmission swap according to costumer. The transmission shifts normal when cold or after removing back up fuse then stays in 3rd gear.

here is a capture during 1st gear.

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Here is another showing 2nd gear command, the car is actually shifting good at this point.

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Slight Lock up - during 2nd gear.

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Replace the bulb, go under the pass seat and see if it has a seperate trans confuser(has 1 led that will blink) ECM has 2 led`s. (CHECK THE GROUND WIRE NEAR CONFUSER`s)Find the jumper connection under the dash panel-pass side, jump to put in diag mode. You can monitor the dash bulb(series 2--or led on confuser--series 1 and get trouble codes. Back in the day they had trouble with the solenoids mounted atop  trans.15 different trouble codes available for that model

Hey Spongebob.HAhaha.
My little girl loves him and I have to admit I do too.
Ronnie. :)

Here is a capture during 4th gear, notice lock up command for lock up =A & B.

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I've been driving this car, still shifting good. We can see proper shift command to the solenoids. Look at this 4-3 capture

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Wrong ECM command to shift solenoids?

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From this point on the ECM no longer upshifts/downshift the transmission.

Sleuth, thanks for your input. I most mention that the ECM/TCM was extremely hot when the car stays in 3rd gear.

We opened the computer and took a look at CKT board; this computer is gone.

Usually we just try another good known computer - after performing basic power/grounds check and flashing codes- on the car to see if simptoms disapear.

I was asked by our transmission guys to play with this car using my pico scope and see its functionality in the transmission repair field.

Hi Rafael:

I am no trans man [smiley=eek.gif]

May I add something to this [smiley=disimulo.gif], if it was getting hot maybe you could of hooked your amp clamp up and ramped it ,to see if you could see anything that way ,just a tid bit for you [smiley=ok.gif]

Thanks for the info keep them coming [smiley=thumbup.gif]

Hi Rich,
I took some captures on shift solenoids command signals  and current ramps. I need to make some final adjustments but I'll post them tomorrow.

TCM command  and current at shift solenoids. Solenoids resistance 16.6 ohms and current reading is about 700mA, well within specs.

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And current capture after about 5 minutes of normal driving, transmission falls in 3rd gear and like already mentioned the TCM gets hot but there are no high current readings. What we found was a couple of burned capacitors.

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Hey Rafael,
Just for grins and giggles, could you put up the codes you got from the TCM? Will be interesting to see what the caps did for diag..Thanks !

Hi Sleuth,

There were no codes.

I jumped the service connector and look at the LED in the TCM - no codes.

Once I drive the car for few minutes, specially during the weird shift feel shown in the captures the LED stays on all of the time.

Ussually when this happens indicates TCM failure. And the captures taken with the scope confirm it.