Toyota Highlander Shifting Concerns

LaMont Owner/Technician Ohio Posted   Latest  
Resolved
Driveability
2002 Toyota Highlander Limited 3.0L (1MZ-FE) 4-spd (U140F) — JTEHF21A320062091
Erratic Upshifts

Good evening fellow technicians. This is my personal vehicle. It has approximately 177,000 miles on it. I recently removed the engine and overhauled it due to oil consumption issues. Before test driving it I thought I would clear any computer memory, since I found a lot of carbon on the intake valves and on the throttle body. I think this is where I made my mistake. I have never had any transmission problem with this vehicle. During the test drive I noticed that when the transmission tries to make a 1-2, or 2-3 shift, it will jerk a bunch of times before going to the next gear. Sometimes it actually jerks a quite a few times and shifts from 1st to 3rd gear. Sometimes it has a delayed engagement from park to drive. When downshifting while pulling a hill, it revs up before finding the lower gear. It just seems like the computer is kind of lost. The function I was in, said something about performing when replacing a transmission or other components. I wish I hadn’t performed it. I assume I have cleared all of the adaptive memory and who knows what else. I have probably driven the vehicle 100 miles hoping it would re-learn things but nothing has improved. The engine runs great and I have no lights or fault codes. Does anyone have any suggestions? I’m out of ideas. Thanks in advance.

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Kevin Technician
Tennessee
Kevin
 

I’ve ran into an issue similar on a different vehicle except the transmission was on its way out then after resetting the shift adaptive in the trans, it made it much worse and never recovered from it, replacing the trans fixed it and now I’d stayed clear from resetting anything unless it’s necessary. I assume you made sure fluid level is still good and did a look over made sure you didn’t miss…

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Creed Technician
Idaho
Creed
 

Besides making sure the transmission fluid is good I would check the grounds on the back of the intake manifold. If these aren't hooked up correctly they can mess with the transmission shifting. If that's all good try relearning the TCM or touching the battery cables together.

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Erik Diagnostician
Florida
Erik
 

Check your grounds on the back or side of the intake. Leave them loose, off or on the body or P/S bracket you will get very horrible shifting. Check it out before you go nuts on the transmission itself. Happened to a Sienna with I believe the same engine trans combo.

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Timothy Owner/Technician
Wisconsin
Timothy
 

As the others have m mentioned, you need to volt-drop the main grounds to the engine at the intake, but I always like to volt-drop them right at the PCM. Also, you should almost never reset adaptives for a trans. that is 20 years old. You may have been right at the limit of the PCM's ability to handle the transmission…especially if you've not serviced the transmission regularly.

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LaMont Owner/Technician
Ohio
LaMont Resolution
 

I unplugged the PCM and used a headlamp to check the integrity of my grounds. Pins 1,2,and 17, which attach to the back of the surge tank would not light the headlamp. I reached my fingers behind the surge tank and immediately discovered that I had failed to tighten the bolt holding those ground wires to the surge tank. After tightening it, the transmission now shifts like it always did. Thanks…

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Erik Diagnostician
Florida
Erik
 

When should I send you my bill? Lol.

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Manuel Diagnostician
New Jersey
Manuel
 

Great work friend

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LaMont Owner/Technician
Ohio
LaMont
 

Thanks. I’d rather owe you than beat you out of it. LOL

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Erik Diagnostician
Florida
Erik
 

Typical flat rate. Never paid just thanked. Lol. Thanks boss! I excel in all things automotive. Time to go back to the gravy…

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Geoff Diagnostician
Hawaii
Geoff
 

Awesome! Side note: All the folks who think the engineers for one part of the car, have any idea about the other parts of the car, need to look no further than multiple ground wires from a PCM all going to exactly the same place. LOL

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Erik Diagnostician
Florida
Erik
 

I was talking to a Facebook group last night and this is way common among 1MZ-FE intakes or the aluminum intakes on Toyota and Lexus ES and RX models. It also causes O2 sensor codes to tweak out too. You think you fixed an O2 sensor high circuit and it turns out to be a loose or completely missing ground. Even seen them attached to the P/S hose bracket in the rear which causes about the same…

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Geoff Diagnostician
Hawaii
Geoff
 

On the late 90's or early 2000's Nissans, many of the flowcharts for circuit codes start with "loosen and tighten" the G101 (or whatever #) on the aluminum intake manifolds. Maybe they sold their factory assembler bolt-installing-robot to Toyota. ;-)

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