I’m sorry but I don’t have a 4Runner please forgive me, however we do share the same gearbox. I have posted my question on numerous Land Cruiser forums and no one has been able to help so here I am.

I have KDJ120 D4D 5 Spd Auto (A750F) UK spec built in Dec 04. I lost 5th gear suddenly so took it to my gearbox specialist who had a look. He tested it, nothing wrong. I picked it up and after about 10 miles it did not go into 5th gear again. He looked at it again, took the valve block out, tested all the solenoids and with nothing physically wrong in the gearbox traced the fault to the Gearbox ECU.

I sourced a second hand ECU and now the car has all 5 gears. HOWEVER - when the gearbox shifts there are ‘shocks’ or ‘bumps’ between various changes. These are upwards 4>5 and when slowing down under braking from 3>2 and 2>1. If I kick down from 3>2 and 2>1 the changes are perfect. The bad Changes are smoother when the gearbox is cold.

In terms of resetting the ‘new’ ECU, the battery had been removed. I have also tried techstream but I get a message saying the ECU can not be reset. Techstream is not showing any fault codes at all. I have done about 400 miles of both highway and urban driving and the changes are, if at all, only getting minimally getting better.

(I have run Techstream 12.x on a Mac with Virtual box with an XHorse 1.4 cable)

I am concerned about long term damage to the gearbox driving while it is poorly. What are my next options / solution…

Prior to loosing 5th gear it ran perfectly.

Thanks and Happy New Year

Wish I had some helpful info for you, but maybe try contacting some aftermarket transmission specialist that make kits for the A750 and they may be able to help.
IPT Performance Transmissions: importperformancetrans.com .
or
Transgo. Don't have their website but Google them.

What was the donor vehicle for the trans ECU? Exact same model/year/configuration as yours? You say you are getting a message that it cannot be "reset" and I'm not sure what that means. I think you may need to do more than just remove the learned adaptions in that ECU (which would happen when you disconnect the battery) but instead reprogram it, Does your Techstream set up and cable supposedly have the ability to program the ECU? It appears you are running a clone, not the official Toyota version Techstream Lite with the Mongoose cable? Assuming your 2nd hand ECU is compatible and not smoked, you could pay to access the actual Techstream site, pull down the correct calibration file and reflash that transmission ECU - might need the Mongoose cable. Or, you take it to Dealership and pay to have them flash it (if they would agree) which would likely be cheaper and less likely to damage your ECU. My thoughts but no guarantee it will fix your problem.

Thank you both.

Yes the ECU is like for like replacement. This is the error I get…




I will try legit Techstream with my xHorse cable. It’s only vsn 1.4 and I think you need 2.x to flash. I’ll have a look at the Mongoose ones.

I will talk the dealer if that fails…

So the reset has to do with clearing the adaptations which is a good place to start. Per the attached article, the battery disconnect is not sufficient for your year. I am not familiar with the Techstream clone capability and limitations.
How To Reset A Toyota Transmission Control Module - Car, Truck And Vehicle How To Guides - Vehicle Freak

My "fleet" is primarily Toyota's and have been waiting to invest in bi-directional control until I had a need I couldn't get around (currently using BlueDriver). When I do, I want it to include flash capability. I decided I would not feel comfortable doing a reflash with a clone so intend to purchase the official equipment when needs dictate. Have been watching the Toyota Mongoose offering - I think they recently released the Mongoose Plus Toyota 3. For a one-off, cheaper to just have someone appropriately equipped do it.

Mongoose-Plus(R) Toyota3

Something else to check is the wiring harness connections at/near the transmission. These are known to get corroded and cause strange transmission behavior.

Thanks. The wiring loom was checked and it’s all is good there.

Excellent. I will try this later on in the week. A question on the process. Do I need to keep the TCM signal wire ground when starting the engine, or just to check it is less that 11v.

Failing that I’ll do the drive and after that find someone to flash it with proper s/w.

Is it likely to be a MAF problem? I’ve been reading a lot lately and my MAF is a little dirty - it is 18 years old!!


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I know somebody else mentioned the wiring loom, but also check the white connector on the driver's side of the transmission, just under the accelerator pedal. Pull the connector and look at all the pins -- I bet you see green corrosion. Spray it all with some De-Oxit, let it dry, and put dilectric grease on the seal to keep moisture out.

I had a similar issue years ago with my '03. This was the problem.

Also after I did the deoxit treatment, I didn't let it dry long enough and sometimes it would start out in third until I sprayed it again, let it dry for an hour. It's been perfect ever since.