Post Trans-Death Issues

[ledzilla]

Ok, so my trans is rebuilt, but before the rebuild I started to get the check engine light, which is still lit, and occasionally the "O/D Off" light will start blinking. The blinking didn't phase me at first because the trans was toast. But now when it blinks it shifts all funny and today it was causing me to essentially accelerate off the line in what seemed like 3rd or 4th gear (manually put it into 2nd so I could still accelerate faster than everyone else). So, can anyone tell me why the damned light would be blinking, and possibly give me some cause to the following error codes? And could any of this be linked with the rapid shifting I'm experiencing, or the bouncing speedometer (which begain after the rebuild)?

P0743
P0750

[lifespeed]

Hopefully they replaced the trans cooler? Don't know who did the rebuild, but incompetence is always a possibility . . .

[sailsmen]

Yea, real simple they FUPED your trans, give them one try to get it all right then report them for fraud.

[RF Overlord]

P0743 - Torque Converter Clutch Solenoid circuit
P0750 - Shift Solenoid "A" malfunction

Check that the wiring harness, more correctly called the "lead frame", is plugged in correctly at all connections, especially at the solenoid pack.

[Krytin]

P0743 - Torque Converter Clutch Solenoid circuit
P0750 - Shift Solenoid "A" malfunction

Check that the wiring harness, more correctly called the "lead frame", is plugged in correctly at all connections, especially at the solenoid pack.

+ 1 on this^ the connector in the oil pan is a little tricky to snap on.

[ledzilla]

The error codes showed up before the rebuild, so I'm not putting any blame on the rebuilder (who has done 4R70W/4R75W transmissions many times). My brother-in-law and I are the ones who pulled the trans out and put it back in. We also replaced three of the solenoids before the rebuild to rule out them failing causing the trans problems. When we did the solenoids, I did notice how funky the harness inside the trans was, though.

[ledzilla]

Ok, so considering everything...

1) What can I do about the torque converter clutch solenoid circuit?
2) Which of the solenoids is Solenoid A? There are the two solenoids mounted together and another kind of buried under the shaft connected to the shifter cable.
3) Why the hell would the OD light be blinking as I drive down the road?

[EMAS]

The OD light is flashing because the computer has detected a fault, and that is it's way of letting you know the problem is related to the trans and not the engine. It flashes since steady on is a potentially normal condition.

[RacerX]

I'd replace all solenoids. TCC (Torque Convertor Lockup Control), Shift (Dual pack) and the EPC (Pressure Control). You can get all three for about $80.00. Just ordered them myself. https://www.wittrans.com/Schematic.aspx?Transmission=AO DE/4R70W/4R75W/4R70E/4R75E&Schematic=6

[ledzilla]

The OD light is flashing because the computer has detected a fault, and that is it's way of letting you know the problem is related to the trans and not the engine. It flashes since steady on is a potentially normal condition.

Ah! Ok, I thought it was something like that, but I wasn't sure if it was blinking for anything specific.


I'd replace all solenoids. TCC (Torque Convertor Lockup Control), Shift (Dual pack) and the EPC (Pressure Control). You can get all three for about $80.00. Just ordered them myself. https://www.wittrans.com/Schematic.aspx?Transmission=AO DE/4R70W/4R75W/4R70E/4R75E&Schematic=6

Thank you for posting that schematic! We replaced the solenoids indicated by numbers 421, 425, and 431 before the transmission was rebuilt. I bought them in a set on eBay for close to the price you mentioned.

[ledzilla]

Additional thought... Considering that it costs less than $30, maybe I should replace the harness. The internals of my trans were pretty bad, and maybe something messed up the harness. The harness wouldn't typically be replaced in a rebuild, would it?

[ledzilla]

It has been suggested to me that the cause of my issues may be a failed TCM (transmission control module). However, I can find nothing for one for the MM. Any thoughts on what I should be looking for?

[RF Overlord]

Our cars don't have a transmission control module. It's all done by the PCM.

[ledzilla]

Ok, so could the PCM be causing these errors? Or would it most likely be either bad replacement solenoids or a bad wiring harness inside the trans?

[RF Overlord]

Although it's not beyond reason that the PCM could be at fault, it's much more common for the solenoids, lead frame, bulkhead connector, or even the DTRS to be the issue.

[ledzilla]

What's the DTRS?

[vegasmarauder]

Pull the connector off the right rear of the trans just above the oil pan mating edge. Take a small mirror and look inside the plastic connector piece that is in the trans case. If you see fluid in there, the plastic connector that fits in the case in that spot is bad. rebuilders may change the O-ring, but the contacts are supposed to be sealed so no fluid should be weeping up into the harness connector end. This fluid wicks all the way up into the actual wiring harness and the Mercon V tends to soften and disolve the wires causing open/short circuits. It's a cheap part and should be replaced during a rebuild, but not all shops will think in a preventative manner. Check the wires near the connector for damaged/softened insulation. The codes tend to indicate an elctrical problem. Usually you start from outside the trans and work you way inside.

[RF Overlord]

What's the DTRS?Digital Transmission Range Selector...it's what tells the PCM which gear you've selected with the shifter. It's mounted to the driver's side of the case.

Also, ^^^what vegasmarauder said^^^

[ledzilla]

Ah! Ok. For some reason I didn't get a notice when these last replies were made. Kind of strange. Anyway, the error light came on before the rebuild, and some of this seems to be references to things after the rebuild.

For all of these items (lead frame, DTRS, bulkhead connector), is there a diagram somewhere or some photos that will help me to see what is connected to where? I don't do well locating things with descriptions. I'm a very visual person and I need to see images that have other things in reference to help me locate parts.

Although, I don't think it has any trouble identifying what is selected. It will occasionally stick in first gear while in DRIVE, but if I manually push it into 2 it will immediately shift into 2nd, although it will sometimes shift up and down between 1st and 2nd until I put it back into DRIVE (where it will finally shift into 3rd). I'm planning to purchase a new internal hard wire harness as I think there is the possibility that something happened to it with debris. I'm not 100% certain about it, but they aren't expensive so I figure it's at least worth a shot. I'm also replacing the speed sensor since my speedo bounces all over while I'm between 25 and 55, and a little bit unsteady at 60+.

[ledzilla]

Additional...

The errors I see I believe point to both the shift solenoid and the TCC solenoid, even though they were both replaced, as the solenoids were originally thought to be the cause of the problem. I wouldn't think the odds would favor getting two faulty replacement solenoids, but I could be quite wrong about that.

[RF Overlord]

I wouldn't think the odds would favor getting two faulty replacement solenoids, Agreed.

The original solenoids may have been fine, but if there's a connectivity issue, the PCM won't be able to determine that they are responding correctly, so it sets errors. This points to the lead frame, as you suspect, or the bulkhead connector or an issue with the wiring harness itself.

[ledzilla]

Just so I know what to look for and attempt to rule it out or repair it, what's the bulkhead connector and where would it be found?

[RF Overlord]

It's the connector that transitions the wiring harness from outside the transmission to inside...it's on the passenger side, toward the back...just above where the pan kinda slopes back. It'll be the only electrical connector on that side.

[ledzilla]

Ah, so that's what vegasmarauder was referring to?

[RF Overlord]

Yes. It's not uncommon...

[vegasmarauder]

You may have residual metal flakes and chips moving around in there. The speed sensor is a magnet pick up in the side of the trans. I have pulled apart shredded trans and found a bunch of metal chips sticking to the speed sensor. You can take it out from outside the trans. It is on the driver's side of the trans about half way up almost directly in line with the last trans pan bolt.

Metal chips would also account for the other elctrical errors. The temp sensor is exposed on the wiring bridge inside the pan. Chips will cause high temp readings and make the OD light flash. Chips in the solenoids will cause no/erratic shifts.

It is hard for some rebuilders to get all the chips out. Almost have to blast the case with a pressure washer. Usually if there is a lot of metal in the pan, the solenoids and pressure regulator have to be replaced. This chips/metal dust gets into everything.

Also, if you don't blast out the cooling lines, you just put metal chips back into a new trans. Some shops will remove the radiator and have it flushed and/or even replaced.

[ledzilla]

Lucky me... My alternator went kaput on the way from work Friday and through a series of events revolving around removing the battery for various testing, upon reintroduction of DC power to the car, the light went out and hasn't come back on for a couple days now.