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Discussion Starter · #1 ·
I've got a 2005 Tundra AC 4X4 (4.7 automatic, 71,000 miles) and on my way home from work tonight the check engine light came on. I then noticed that it seemed to be stuck in one gear, third I think. Whenever I would let off on the gas it seemed like it was going into neutral, rpms would drop from 2500 down to around 900. As soon as I would push on the gas pedal again the rpms would go back up to what they were supposed to be, kinda like going from neutral to 3rd. When I got about a half mile from my house I stopped it and dropped the shifter into 2nd, 3rd, and drive. It would go into each gear, but it won't shift on its own. Anyone have any ideas?
 

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05' Tundra (Tun-Tun)
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weird...ive seen it not shift outta first because of a speed sensor (stratus). but to be in 3rd is puzzling...
 

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Is the trans oil temp light on too? I think there is a "limp home" fail safe mode that locks it in 3rd. It can be activated by problems in the ATF temp sensor circuit or the coolant temp sensor circuit. I'm not sure if it would go into the other gears if this was the issue though. You probably can't do much without checking the fault code. FYI, I recently got a very basic code reader from amazon.com for $35 shipped 2nd day air. Nothing fancy, but it more than pays for itself the 1st time you use it.
 

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Discussion Starter · #4 ·
Trans oil temp light is not on, just the "check engine" light. :confused: Engine temp was normal, and oil pressure was normal. Could it have something to do with a solenoid somewhere in the tranny?
 

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Is the trans oil temp light on too? I think there is a "limp home" fail safe mode that locks it in 3rd. It can be activated by problems in the ATF temp sensor circuit or the coolant temp sensor circuit. I'm not sure if it would go into the other gears if this was the issue though. You probably can't do much without checking the fault code. FYI, I recently got a very basic code reader from amazon.com for $35 shipped 2nd day air. Nothing fancy, but it more than pays for itself the 1st time you use it.
hi, great idea as to what it might be. also i have the scanguage2 that tell's me what code it is. as many of us have. the only thing i see with that is what good is the code, if it doesn't tell you what the code means. so you have the code, now you need to take it somewhere , & have them check it anyway. and they are going to have what you just bought. not only does it show the code, but it tell's you what the code is. now you can go buy the part or at least know when you bring it in to have it fixed, not be BS'ed by the shop.
excellant idea. :first:what type is the best all around to buy. what is the low to high price of 1 new?
point's given.:angel:
gorilla
 

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One thing I've been starting to see more commonly is corrosion in the ECT connector on the driver side of the trans. This can cause high resistance to one of the shift solenoids and throw a code or if one or more of the pins have broken off creates an open circuit. Without knowing the code I can't be positive but this is easy enough to check yourself. Crawl under your truck and disconnect the largest connector on the driver side of the trans. It's towards the middle right behind the shift selector rod. It has a white locking clip you need to pivot down to release. Then just look for green corrosion in this connector. Some pics can be found here: Tundra trans
 

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Discussion Starter · #7 ·
I forgot to mention this: Before it seemed to get stuck in one gear, I was behind a slower moving vehicle and kept having to slightly accelerate and then let off on the gas to keep my distance from the car in front of me. It seemed like my Tundra was very sensitive to this slight throttle modulation and would upshift and downshift very frequently, something it had never done before.
 

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I posted this in January. This could be your problem!
My Toyota Tundra 2005, V8, 4.7L, 4x4(83,000 miles) lost its transmission power while driving on the highway and the check engine light came on. The transmission power came on and off all the way home. Lunging each time it dropped off and came on. I brought it to the dealer who told me I needed a new transmission at a cost of $4000.00. It was displaying P0986 code.

The next day I brought it to a transmission shop. They found that the wire connector (15 pin) that goes from the transmission to the ECM was corroded and the pins were broken and not making contact. Its design is clearly defective. It is not protected and is located in a place where it is exposed to all the salt and water resulting in the pins being corroded. Information communicated from the computer to the transmission and back is interrupted or inaccurate. I found this information on a website at the same time the independent transmission shop discovered what the problem was. The following site describes the problem very clearly: Tundra trans

The cost for the new male harness was $58.00. The pan needed to be dropped to replace the harness and the broken pins needed to be picked out of the female harness. Labor and fluid was about $460.00. I contacted Toyota. They gave me a run around with only frustration and stress. I see this problem occurring with all these trucks in any part of the country where it is wet. The dealers only replaced transmissions and don't fix them. Anybody else have this problem? Learn from me if you have problems with your transmission check the connector first!
 

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Like all said, you'll have to access the codes. I'm no trans guy, but it doesn't sound like the typical "terminal death" symptoms of the transmission. Sounds more solenoid/sensor/ecu related, since it will still operate in all of the gears. The first thing to do with an automatic is check the fluid, but I don't think the 05's allow that capability. I guess you could try to disconnect the battery for a minute or two. Sometimes that will sort of "reset" a confused sensor, if only temporarily. Good luck and keep us posted.
 

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Discussion Starter · #10 ·
Soon as I have some breakfast I'll go outside and check that, BlackIX. Thanks for the heads-up. Just read your posts, bgeorge and bamafire. Thanks for your input as well. I have a mechanic that I trust and take my vehicles to and will be taking my Tundra to him tomorrow.

I should also mention that he previously had to fix something in the engine harness that caused my Tundra to shift a lot harder than it was supposed to. This happened back in July. He said that whatever it was (like I said, I am unfamiliar with modern engines and their vast array of electronics) it was not correctly sealed from moisture from the factory, but I do remember him saying it involved the engine harness.
 

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I am going through the same process Bgeorge just mentioned, same code too. I just bought the truck last Wed. with a known trans shifting problem. It had previously been to another Toyota dealer and they replaced a solenoid in the valvebody. I'm a Toyota mechanic myself and it's a rather simple fix if you know what to look for. If your connector is clean though, then you might be in trouble. This is the only common trans problem I have seen on Tundra's.
 

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If you search out my original post "05 tundra transmission problem" and click on the Tundra tran link, there is a clear picture of what the connector looks like.
 

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The pictures can be accessed in BlackIX first post. I suggest you print a copy and bring it tomorrow when you bring it in!
Keep us posted on what you find out.
 

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Discussion Starter · #14 ·
The pictures can be accessed in BlackIX first post. I suggest you print a copy and bring it tomorrow when you bring it in!
Keep us posted on what you find out.
Will do. I found the connection you were referring to, but didn't want to mess with it.
 

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Trans oil temp light is not on, just the "check engine" light. :confused: Engine temp was normal, and oil pressure was normal. Could it have something to do with a solenoid somewhere in the tranny?
It could be a problem in the coolant temp sensor circuit. It doesn't actually have to overheat.
 

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My old taco did something very similar, ended up being the neutral safety switch that is mounted on the side of the transmission, $450 dollar part and about the same for labour at the dealer to find it
 

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hi, great idea as to what it might be. also i have the scanguage2 that tell's me what code it is. as many of us have. the only thing i see with that is what good is the code, if it doesn't tell you what the code means. so you have the code, now you need to take it somewhere , & have them check it anyway. and they are going to have what you just bought. not only does it show the code, but it tell's you what the code is. now you can go buy the part or at least know when you bring it in to have it fixed, not be BS'ed by the shop.
excellant idea. :first:what type is the best all around to buy. what is the low to high price of 1 new?
point's given.:angel:
gorilla
Find the code and google it. You'll be surprised at the information you'll receive and lot's of info on how to fix or continue testing.
 

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Find the code and google it. You'll be surprised at the information you'll receive and lot's of info on how to fix or continue testing.
That's why I bought the cheapest code reader I could find. I couldn't justify spending $100 on a scanner when there is so much free info online.
 

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Discussion Starter · #19 ·
I found out what the problem is. My Tundra needs a new engine harness. My mechanic had previously fixed it with a bit of soldering, but he just told me it is now beyond repair. Oh, the good news? You have to buy the entire engine harness, to the tune of $880.00. Plus labor. Why is an engine harness on a 5 year old truck corroding? Where is this thing located?
 

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The engine harness consists of all the wiring from the sensors, etc. to the ECM. Were there several engine codes? I'm surprised he can't just repair the wiring in the problem circuit.
 
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