P0778

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TwiceWithHair

TwiceWithHair

10 Year
Joined
Sep 27, 2011
Threads
13
Messages
404
Location
Truckee, CA
Driving my girlfriend to work, dashboard lights up. Ugh... check gauges. all fine. engine running smoothly. I chance the extra block to her work before checking it out in the parking lot. slowing down to a stop, there was a THUNK! not a drive-shaft-needs-lube thunk. I have that too. its different. Car off. hood open. all fluids that i can check are fine. no noticeable leaks. i start up the engine again after deciding it probably had something to do with my brakes. those have sensors, right? so I decide to drive home to my computer using the hand brake (~3 miles). During the drive, it THUNKED around 5-7 mph on slow down every time. pedal brake or hand brake. now I'm thinking its first gear. sure enough, manually shifting to 1st THUNKED hard. so i push the 2nd button. thunk is gone the rest of the drive. first gear is mad at me. get home to a computer and verify p0778. shift solenoid b. do i have an electrical problem? a transmission problem? or a low fluid (with no dipstick to check) problem? search had ZERO results for this code.

2004 LC @120,000
 
^ have not crossed this bridge yet...hopefully never will. I just lightly/quickly perused the 2004 Diagnostic section of the FSM: Can you shift the AT manually through the gears? "The ECM commands gearshift by turning the shift solenoid valves "ON/OFF".

"Manual shifting as shown in the following table must be done (In the case of a short circuit, the ECM stops sending current to the short circuited solenoid)."

Also found this:
Causes
Possible causes of OBD code P0778
- Faulty line pressure solenoid valve B - Line pressure solenoid valve B harness or connectors - Line pressure solenoid valve B circuit is open or shorted - Low transmission fluid level - Dirty transmission fluid The Error code is generally activated on detection of the following conditions: Engine Control Module (ECM) detectes an open or shorted condition on the solenoid circuit
 
I CAN shift through manually. It shifts automatically as well. But second gear to first gear has THUNK whether shifted manually or automatically. To my knowledge, fluid has never been changed. I bought her at 86,000

I remember reading a thread about someone who's issue was fixed by simply adding fluid. Maybe I'll start there, but how do I check fluid level?


...via IH8MUD app
 
What MY do you have?
 
On the '04 there is a refill plug located at the rear of the transmission. Per the FSM: The AT should be filled from the refill plug (plug removed of course ;)) until fluid begins to begins to flow out the Overflow tube (located at the bottom of the AT pan (with overflow plug removed).

Mine is a '99 with the A343F 4-sp AT therefore I do not have direct experience with above...PM me your e mail addy and I'll e-mail the FSM pages relative to this for you. Dan
 
Too busy? Too lazy? Lack tools? Pick your excuse, I towed her to Toyota.
ImageUploadedByIH8MUD Forum1426290650.514508.webp

To my surprise, they told me she got a new transmission at 54,000 miles. She's at 120,000 now with another transmission issue. I thought the 5 speed was bullet proof... Previous owner must've done a lot of towing? Stock height, stock running boards and tires bald enough to have been from the factory when I got her. Not sure how else she could've been abused. I'd hate to think the car I love is a lemon, but man is she nickel and diming me as if she were a ford.


...via IH8MUD app
 
TwiceWithHair said:
Too busy? Too lazy? Lack tools? Pick your excuse, I towed her to Toyota. View attachment 1044915
To my surprise, they told me she got a new transmission at 54,000 miles. She's at 120,000 now with another transmission issue. I thought the 5 speed was bullet proof... Previous owner must've done a lot of towing? Stock height, stock running boards and tires bald enough to have been from the factory when I got her. Not sure how else she could've been abused. I'd hate to think the car I love is a lemon, but man is she nickel and diming me as if she were a ford.


...via IH8MUD app
Click to expand...

WOW keep us informed
Bad 5sp are rare and even more so at 54K
Does the trans leak any?
Hopefully something simple
You can replace the pan with a 03 (last year for the dip stick and the only 5sp to have one in a 100 series) and get a dip stick for ~$175
 
Toyota called me back today. Said solenoids are fine and fluid looked clean. They said the issue is my transmission wiring harness. They are ordering me a new one. Now we play the waiting game as shipping to Maui takes a little longer than other places.


...via IH8MUD app
 
TwiceWithHair said:
Toyota called me back today. Said solenoids are fine and fluid looked clean. They said the issue is my transmission wiring harness. They are ordering me a new one. Now we play the waiting game as shipping to Maui takes a little longer than other places.


...via IH8MUD app
Click to expand...
i rather be waiting in maui than any other places.... hahahah hope that fixes the problem.
 
Which harness are they replacing, the one inside the transmission that attaches to the solenoids or the one from the ECU to the transmission? I had similar weird issues with the 5-speed in our 4th gen 4Runner (same A750 trans) - wouldn't shift out of first automatically but would shift manually, albeit very harshly with a clunk in every gear. Had P0778 along with a bunch of other codes.

Turned out to be two pins that somehow rubbed through the plastic divider in the connector from the trans harness to the ECU and were causing an intermittent short. Just something to look out for, since I also did a bunch of googling at the time and found NOBODY with similar issues anywhere. Ended up replacing just the connector (after spending lots of other useless time and $); no issues in the past 2 years.
 
They said "harness." I don't know the specifics, but they sounded confident it would fix the problem. Don't jinx it! I've been without her since mid FEB. I just want my truck back already.


...via IH8MUD app
 
I called Toyota today. Upset. They've had my truck for 3 weeks now. They said "turns out you wiring harness is fine and all your solenoids work fine. We found metal in your pan though. You need a new transmission." They quoted me $4300 for PARTS.

I asked them to please put my truck back together so I can come pick it up. I'm 6 weeks without a car now. I'll be driving it off the lot (assuming they didn't break it more) with the "2nd" button pressed as to avoid 1st gear. I think I need a second opinion. Thanks Toyota... (Sarcasm)


...via IH8MUD app
 
Ouch!
 
hurts more to see her inoperable in my driveway. she drove home just fine. 12 miles with the 2nd button pressed. i plan to drive it back to town for my second opinion. which won't be for at least 3 more weeks. only 2 shops on island and they are super backed up. might have to find a moped on craigslist to get around in the meantime.
 
Wow, that's sad I feel your pain, I went through something very similar with my ex 85 mini truck with the electronic controlled A340H auto trans. Before you have the trans replaced find a mechanic that will pull the valve body out and take apart and examine. Some like the asin Warner a340h that can be done without pulling trans good luck.
 
Yup. Yogi is supposed to be the man on island. He's on vacation right now. Patience might save me money. There is no time saving method. Island is slooooooooow. This thread will bump back up when I get my second opinion.


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