A750F / A750E P2716 wiring harness short FIXED!

Anyone ever pulled this code and successfully found a wire that was shorting out in the main ECU harness? I've checked what I can visually and can't see a bad wire. Wondering if its possibly a wire that's shorted in the transmission itself? It's the only code being thrown. Even with the truck in the on position not running it throws this code.

Tomorrow I'll be able to crawl under and hopefully test the resistance through the plug on the transmission and narrow it down. As shown in the diagnosis literature.

@gearcruncher any ideas?

 

If it is a short you will have open circuit protection , melted wires or a visit from the fire department

If it is a open circuit it might be something as simple as a corroded connector a bent pin or physical damage to the wires .

Always possible the ECM got wet or had a voltage spike about the only thing that will cause them problems

Time to break out the meter

 

Here is one possibilty listed below not directly related to code 2716 a common complaint . You are on the rite track . Measure the resistance of the wires at the case connector next .

Toyota A750E/F with Multiple Solenoid Circuit Faults
Toyota Tundra, 4Runner, Tacoma, Sequoia and FJ Cruiser equipped with the A750 transmission may exhibit a complaint of multiple transmission solenoid electrical circuit faults set. Typically, to have multiple solenoid electrical faults indicates that there is a power loss or ground problems, possible compromised wiring harness (pinched, broken or melted0, or a connector is not plugged in all the way or completely disconnected. In this case, the cause may be, a bad weather pack seal on the harness side connector of the transmission case connector allowing moisture to corrode the male terminals and or deteriorating them. It is not uncommon to remove the external harness connector (female) and see the male terminals from the case connector, as shown in Figure 1, still stuck in the harness connector when this happens.



To correct this condition, replace the transmission case connector, which is part of the internal harness, and clean the terminals in the female external harness connector. Install a small amount of dielectric grease into the connector and a small amount of silicone sealant on the weather pack seal to prevent moisture.

Internal Harness (04-4Runner, Land Cruiser): 82125-35130

Internal Harness (05-Sequoia, Land Cruiser, Tundra, Tacoma): 82125-35150

Note: Contact your local dealer for vehicles other than shown above.

Did you find this helpful? Comment below. Thanks!

https://www.atsg.us/atsg/blog/toyotaa750efmultiplesolenoidcircuitfaults/


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More info here http://www.customtacos.com/tech.old...06toyrm/06toypdf/06rmsrc/rm2006ta/0270029.pdf

 

Thanks guys.

 

@Wyoming09 @gearcruncher. Got the pan dropped today for inspection on the internal harness. Is sediment like this common in the pan? Looks to be aluminum, but maybe brass? Looks mostly like aluminum discolored by the ATF.

175k on this truck.

Visually inspecting the wiring harness currently. Specifically the wires leading to the SLT solenoid.

 

Well after some research, and friends opinions, I've got limited life left in this transmission. Looking for solutions to low mileage replacement and or rebuild.

 

Those pictures do not do the transmission justice . It is soo difficult to tell how much contamination there is . How deep is the brass and alluminum ?
Has the trans ever been serviced ?
Anything stuck on your magnets . Be sure to remove the filtter .
This why you pan drop rather than go directly to a transmission flush .
Can you imagine forcing all that crap through your transmission cooler
And the trans seemed to function fine ?
Any luck finding a broken wire ?

 

I saw a few spots where it looked like the sheathing on the wire harness may or may not have wore through or gotten pinched between the valve body and the filter/screen housing. Tried to adjust the sheathing to cover up those spots, still throwing the P2716 code. Magnets where coated with a metallic paste. Trans was flushed approx 25k ago after I first bought it. Bought it with 143k, up to 175k now. The sediment in the pan was not too thick, looked more like I was panning for gold with the amount in there. It never really felt right to me, and I guess this is how it ends. For the last 10-15k I've been strictly using 4th on the shifter, instead of placing it in D. It would hunt between 4th and OD around 40mph. Also I would notice that it really took it's time to get out of 4th and into OD on the highway at cruising speeds. After the filter change and 4qts of new ATF, it seemed a little better mannered last night on a test run and this morning on the way to work.

One more question for you @gearcruncher will any a750f interchange with my truck, or are there certain years that will only fit an 06 Tacoma? I see it has been offered throughout Toyotas lineup, Sequoia, tundra, 4runner, Tacoma, and fj cruiser. Looks like some Lexus suv's also. A few vendors told me my interchangeable years where 05-07 tacomas only.

 

you are good for 05 -2007 tacomas . They are cheap to purchase second hand cuz they are a dime a dozen .

 

Before you replace the transmission check the valve body harness located on the driver side of the transmission, its somewhat common for water to get into the connector and corrode the pins, if its rusted you will need to replace the pig tail of the harness and the valve body harness which you can get at the dealership.

 

Yeah I pulled that off, looked clean with some electrical grease in there. I also checked the internal part of that harness when I dropped the pan for a filter change. Only thing I didn't do was test continuity through each wire it while the pan was off. I saw a few questionable spots that looked nicked or pinched above the filter where the solenoid d wiring is routed. In hindsight I definitely should have tested continuity to determine if my issue is the body harness or even the ECU.

 

You can check threw the ecu connector this way your testing the harness, transmission harness and solenoid. Green wire with black tracer and
red wire with a black tracer. if something is off test from the ecu to the transmission connector to determine if its in the harness or the valve body. I have never seen a tacoma ecm fail.

 

This coming weekend, I am going to have to pull the transmission to replace my rear crankshaft seal and saw this external transmission connector that I will have to remove.
How do you remove this? I also have a question about how to remove the two harness clips so that I can drop the transmission. here is a pic of the additional connector I have a question about.
is the tab with the arrow the release point?

Any help would be appreciated.

 

That should just push right off the holder it's clipped to. It slides on to that bracket thats bolted to the transmission housing. I think.

 

Any advice on how to disconnect the external transmission connector shown in your pic?

 

That one hinges. Rotate the hinge to release pressure on the plug and it will swing away from the harness allowing you to pull the plug apart from the transmission.

 

@bobsuruncle - Thanks for the information. It's very helpful.
I would hate to get to the point of dropping the transmission and then not be able to figure out how to dettach the connectors and harness.

 

Btw it looks like there's another plug right at the top of the bell housing on the backside of the heads.

 

Yes. I noticed that as well. it seems to have a rubber hose with a clamp on it. Hopefully I can reach it with some long needle nose pliers and get it off.
I guess I will have to tackle that when I get there.

Thanks again.

 

Well today, not sure when, my check engine light went away, and the transmission went back to shifting normal. The code is still stored in the ECU, but not currently active. Not sure what the deal is but I'll be keeping an eye on it. Have a feeling I'll be seeing the CEL again. These types of issues don't normally just go away.