Shifts in-n-out of OverDrive...

My '96 Limited SR5 4x4 4Runner, new to me this year, wouldn't go into OD. It would switch in and out constantly

Here's a video of it: https://youtu.be/-VauaC_cUlA You can't see but I'm between 60 and 70mph while it's doing this.

...long story short, I've replaced the trans fluid and filter, shift solenoids (A,B and LockUp) and finally, the thermostat, which seemed to fix the problem.

The theory at the time was the thermostat was regulating the engine temp to low. The ECU would signal the trans to lock out the OD until the engine was up to temp, etc...there are other threads on here regarding low engine temp and OD.

Since the thermostat change (more than a month and counting) the truck has exhibited this problem twice, for short periods of time. Otherwise it drives great: no rough idle, doesn't stall, plenty of power in all gears, normal fuel usage...

The new twist: we left for four days to visit relatives in Mississippi and Louisiana. The day after I got back I took the family to the beach in the truck (which had been sitting for 4 days) and it didn't shift into OD until we were coming home, then the crazy search and shift, then normal...I drove it to work, ran errands over the last few days and no problems??

I've talked with a mechanic and the new theory is either a short in the wiring between the lock-up solenoid and plug on the outside of the transmission or between plug and ECU or the torque converter clutch is bad. The mechanic seemed to think it was the wiring since the pan was relatively clean when I changed the fluid.

My questions: where can I find a pin chart for these plugs so I can test the wires? Also, any thoughts on how likely a wire short would be to cause this kind of problem? Anyone with any experience dealing with torque converters?

You can also check all your brake light bulbs and turn signals. Sometime a burned out bulb can backfeed voltage to the stop lamp circuit, which will unlock the torque converter.

Usually those symptoms only manifest when you activate the turn signals or flashers though. So maybe not...

Certain can't hurt to check all the stop lamps, and trailer wiring if you have that too.

Wish I could help.... But that problem is bigger then my little brain and I would be clueless... I would hunt down a real Toyota service manual and dig through that for the wiring diagrams.

turbodudey2: Fair enough. The right side running light is out. I suppose anything is possible? Was planning to replace it this weekend anyway.

psraff: Unfortunately I feel the same way, haha! It's still driving great. It hasn't done the shifty thing since we got back from the beach that day, running great...

At it again...

This time we left for California for 2 weeks, got back and it doesn't shift into OD at all...ever...Same as before, it drives great, no hard shifting, sluggishness, no check engine light??

Toyota says I need a new transmission. I've had a scanner on it and it's not getting a signal to shift into 4th gear. I tried the "manual shift test" and 4th gear is there, it's fine. Something is wonky with the electronics...

Update:

Some car problems are hard. Anyway, in the interest of full disclosure and for fun I thought I would update this string.

Last week, as my wife was driving through our neighborhood on the way home from the store, our 4Runner just stopped working. She said it sputtered and lurched like it was out of gas, the dash lights all came on, and it coasted to a stop...We had it towed to our local service station (not the dealership.) They were not able to connect to the PCM via the OBDII link, no communication, and proceeded to manually test the different systems to see what might be the problem. Eventually they conceded that the PCM itself must be bad.

They found a used one at a local junk yard, installed it and the truck is back up and running. Only time will tell but, so far, no shifting problems.

I had previously thought the PCM might be bad, even debated the pros and cons of replacing it with my dad, but had an impression that was less likely a problem than it turned out to be. My mistake cost me about $500 in diagnostic testing (a used PCM is relatively inexpensive and dead-simple to replace.)

Thanks to everyone who replied here. I really appreciate the time.

I was having OD shifting problems for the past few months. I replaced my ECU for a seperate issue with a used one and now my shifting problems are gone. I think the ECU may be to blame for more issues than we realize. If only the remanufactured ones weren't so expensive. It might save a person some money just swapping ECUs out with another 4runner that has no problems just to confirm.

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The ECUs are getting to the age where they can start having capacitors go bad... This makes sense based on the OP's symptoms (though I wouldn't have thought about it before knowing that a new ECU fixed the problems).

Very fixable if you have the right tools... but most people aren't really qualified to get inside an ECU.

-Charlie

I was having this issue and it ended up being a loose connection at the O/D button.

As a side note I have also seen people mistaken a misfire at load on the highway as OD going in and out.

used PCM

I thought about replacing the PCM but my shifting problem was not consistent. It could've run great for weeks and then, after it was to late to return the used PCM, started showing problems again. That and just thinking that a solid state computer like that should last was why I held back.

Glad to hear you got lucky. Live and learn.

ZionXIX said:

I was having OD shifting problems for the past few months. I replaced my ECU for a seperate issue with a used one and now my shifting problems are gone. I think the ECU may be to blame for more issues than we realize. If only the remanufactured ones weren't so expensive. It might save a person some money just swapping ECUs out with another 4runner that has no problems just to confirm.

Sent from my SM-G930T using Tapatalk

Click to expand...

Down by the Water said:

I thought about replacing the PCM but my shifting problem was not consistent. It could've run great for weeks and then, after it was to late to return the used PCM, started showing problems again. That and just thinking that a solid state computer like that should last was why I held back.

Glad to hear you got lucky. Live and learn.

Click to expand...

Luck had nothing to do with it. I physically looked at my board and observed blown capacitors and nasty electrolytic fluid corrosion covering a quarter sized spots on the board. It was fairly obvious that was contributing to my issue. I never imagined it would fix the transmission shifting too. Like I gradually lost the ability to shift into O/D. Glad it's back though.

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loose connection

Jay,

I tested the voltage at the button, in and out, and it all checked out.

I unplugged the shift solenoids and was able to shift through all the gears manually so that was good...as I noted before, it purred like a kitten otherwise.

I may really lose my s&%%t if the problem comes back, haha! For now I'm just happy to have her back on the road.

JayRolla said:

I was having this issue and it ended up being a loose connection at the O/D button.

As a side note I have also seen people mistaken a misfire at load on the highway as OD going in and out.

Click to expand...