This is a 4-cylinder (5SFE) Camry, correct?

In your photo, the red arrow points to connector E3, part number 90980-11156, having female pins. The male side goes to "shift solenoid valve SL." If the connector is not fastened properly, then yes, P0773 will be thrown.

It sounds like the male pin side may be damaged.

Release connector E3 by pressing on the tab where the green arrow points below:

Inspect and clean the mating surfaces with a rag and Q-tips as best you can. Take photos of the two mating sides (male pins and female pins), and post them here.

Normally to fasten the connector, push gently and simultaneously, listen for a "click." If you hear the click, it is most likely fastened correctly.

Reference:
1999 Camry Wiring diagram page 208.

 

Thanks for the help. Here are the parts in question. The first one is the dust cap that fits over bit on top of the trans into which the connector you described is plugged.

And this is the inside. There is one tiny nub of a lead that has continuity to the lead on the other side that slots into the connector.

Finally this is the part over which the dust cover fits. It’s right behind the connector for the neutral safety switch

my assumption is that this connector E3 you are talking about connects to it somehow but I just can’t figure out what slots into what. If you could shed some light on that I’d very much appreciate it

 

The so-called "dust cap" (a.k.a. "male pin connector housing") that your photos show in post #3 is //not// designed to come off. Someone or something broke it. This "cap" is integral to the lock-up solenoid, p/n 85420-20110. Because this "cap" now comes off, I suspect a soldered wire connection or similar has broken. Soldering (or whatever) was done at the factory.

I do not know the "internals" of the lock-up solenoid well enough to say whether this is repairable. I think the best choice is to buy a new lock-up solenoid or get one from a salvage yard. EBay has them. I would buy only either a Toyota OEM solenoid or if you can find one made by Denso, then buy the Denso (probably for somewhat less). Just search eBay and the net for the part number I gave above.

Photos of the lock-up solenoid when it is not broken:

It's not a standard harness plug but a rubber dirt gasket with an odd assortment of prongs.

Before the male pin side of the connector got broken, it //was// a standard harness connector.

 

Thanks for all the info. To be honest I actually wasn't aware that the part could come off. There is so much crud around the base that the bolts were hidden. I've purchased a replacement lock-up solenoid but the USPS currently has it in package purgatory. I took the old, broken one off today and once the replacement arrives I'll attach it and let you know if that did the trick.

 

Replacement finally arrived and installed. Engine runs fine. Shifts and drives, at least in lower gears as I've only driven it around the neighborhood, but the CEL remains on. All my car mechanic experience is with older, pre-ODBII cars so I'm not terribly familiar with how this works? When is the light supposed to turn off? I've read something about having the appropriate number of "warm up cycles" go by before that'll happen, but I'm not sure what that means.

 

the CEL remains on. ... When is the light supposed to turn off?

Have you tried either --

-- resetting the CEL using your code reader?

or

-- disconnecting the battery for a few minutes (maybe a half hour for insurance)?

As long as the computer is not throwing a code, both of these normally turn off the CEL.

 

Resetting with the code reader didn’t help but unplugging the battery for a bit did. However while the original problem seems fixed I now get a new code: P1780. I know this has to do with the neutral safety switch, but as far as I can tell it’s fine. I actually replaced it recently so I doubt it’s broken. All lights work and the car starts and drives as expected so I’m not sure what the issue is. I’ve cleaned the contacts with Deoxit and unplugged the battery again to see if that clears it, but if not any other suggestions?

 

I hear you about the code P1780. I am studying the Camry service manual diagnostics section and the wiring diagrams as we speak. I suspect this is a wiring problem and not a switch problem or an ECM (engine computer) problem.

First, in post #1, first photo, tell me about the blue plastic housing that seems to have a black/white wire passing through it. Is this blue plastic housing a wire connector? Please provide photos showing all wires connecting to this blue plastic housing. Please tell me what you know about this blue plastic housing. Because if it is supposed to be connecting wires, it may not have a good connection. Code p1780 is the likely result, by my reading of the diagnostics section.

You are the boots on the ground there. If you think that blue plastic housing is not doing whatever it was supposed to do, discard it, and then check back here for my recommendation on splicing wires.

Edit:
I attach the service manual P1780 diagnostics section.

 

First, in post #1, first photo, tell me about the blue plastic housing that seems to have a black/white wire passing through it. Is this blue plastic housing a wire connector? Please provide photos showing all wires connecting to this blue plastic housing. Please tell me what you know about this blue plastic housing. Because if it is supposed to be connecting wires, it may not have a good connection.

The code did, of course, come back, so I'm sort of back to sqaure one.

Anyway, the blue plastic housing seems to be a clamp that has a metal bit in the middle that I think shorts the two wires that go through it. In my case they were black-white wire and a grey wire. I don't know why this is. I've taken it off in the meantime to see if that makes any difference.

I regards to testing the wiring, the docs you shared have been useful but for the life of me I just can't find a clear pinout of the NSS harness, so I honestly do not know which pin is which. The pins look like this

Which is which?

 

So I took the instructions from the doc you shared (thanks for that) and did my best to follow the directions that use a multimeter rather than Toyota's special test tool which, unsurprisingly, I don't have. It wasn't super clear from the tiny diagram which pins I was supposed to be testing, and I was getting some odd voltage readings on most of them. They tended to either have no voltage or between 4 and 6 volts. Anyway, long story short when I plugged all the ECU connectors back in the code went away. Hurray I fixed it! Maybe the pins were dirty and unplugging and replugging sorted it out? I have no idea.

Anyway this should be good for inspection. Many thanks for your help, Elle.

 

Let's see if the code comes back.

 

Which code came back?

Here are the pin numbers et cetera:

Pin 2 = red/blue wire to 10A gauge fuse and so 12 volts (Key on, EOff?)
Pin 3 =blue/white to combination meter, indicator light for 2nd gear.
Pin 4 = yellow to combination meter, indicator light for low gear (1).

Pin 5 = black/white to 5Amp starter fuse
Pin 6 = gray to engine computer

Pin 7 = green/white to combination meter, indicator light for Park
Pin 8 = red/black to engine computer and back-up lights, left and right, rear
Pin 9 = red to combination meter, indicator light for Neutral
Pin 10 = black/red to combination meter, indicator light for Drive and also cruise control

I am traveling in the mountains and frequently have no internet. I may not be able to give this thread the attention it deserves until Saturday or so.