Hi guys,

My truck is firing code P0770 and I need help. Have any of you had this same issue in the past? If so, how did you fix it?

I have a 2001 4x4 with an A340F. When the code first fired I changed the three solenoids and that did not fix it. I did a trans fluid filter change and flush when I did the solenoids. The pink milkshake NEVER happened. The truck drives and shifts fine, even at highway speed. Only thing that happens is the Trans lol temp light saying the trans oil is too hot comes on when I drive on the highway for extended periods of time.

I went to a tranny shop and he scanned all the solenoids while we drove the truck and none of them showed the OBD2 sensor any data, which made him think the TCM is bad. So he recommended going to the dealer to diagnose.
Or going to a junkyard and trying a new TCM and swapping mine out.

Where is the TCM? Is this a possible fix you think?

Based on these conditions can anyone provide some insight as how to proceed?
I have read that the fluid pump bushing may have gone bad and is causing the code. Also the service manual tells us to change the solenoid and then the torque converter. What do you think?

I’m lost and not sure how to proceed. I could put in a transmission but that won’t fix it if it is a bad TCM. Also a TCM is much less expensive than a new transmission.

Please help,
Mike

Here is the diagnosis procedure straight from the FSM:

Trouble areas: Shift solenoid valve SL is stuck open or closed
Valve body blocked up or stuck
Lock-up clutch

First thing the book says to check is the operation of the shift solenoid valve SL by removing the trans pan, removing the solenoid valve SL and applying 71 psi compressed air and making sure it doesn't leak air. Then it says to apply 12 volts to the solenoid and make sure that it opens. If it fails those tests, replace it.
If it passes those tests, move on to the next.

It says to "check the valve body" and refers you to page DI175 of the FSM. When you go there, it has a list of things that are not operating properly and then refers you to the A340f repair manual. Most of those would be expensive repairs and a trans replacement would probably be the best bet.

If everything checks out up to this point, it says to replace the torque converter.

So... We need to know from you, are there any funny symptoms that the trans is exhibiting? Is the torque converter locking up when it should? (usually between 40-45 mph on light to medium throttle load).

There is no transmission control module (TCM) for these trucks. The transmission is controlled by the main ECM.

That 'only' thing is a really big one that may be contributing to a shorter life overall for the trans components.

Have you checked the actual trans temps via something like scanguage, torque, ect? If it is higher than 200 or so it needs to be determined why.

i just got the same code. along with p0440 for evap.

my 01 has got a bit of a tran fluid leak, so based on past success i put it a bit of the transmission seal restore fluid, topped it up and went on my way. recently did a 100 mile roundtrip and thats when the engine light came on.

its slams a bit between drive and reverse, not horrible, but noticeable. freeway driving was mostly fine. but on freeway going uphill gear shifting seems a bit slow to me, but coming from a 03 with V8 i'm not entirely certain this is true as the power and torque is WAY different.

as im writing this i realize i havent checked fluid level since adding the restorer. d'oh.

assuming level is ok, i'm wondering if i should first start with a fluid replacement? go straight to a fluid flush? wondering if something reacted and solidified and could be partially blocking the shift valve....

dont think replacing shift solenoid valve is too difficult is it? for less than 100 bucks i'm fine with swapping it out if the problem continues.

Yep I get that from time to time, reported as P0770 $10 Generic by a basic Ancel reader: Shift Solenoid E My Ultra gauge just says P0770 I believe.

While I'm at it, I see a P0120 as well: Throttle/Pedal Position Sensor/Switch A Circuit