Hang on to your pants! We've got a "p" Lock triangle of death mystery.

Here we go, a mystery on our hands. I have searched this sucker.
I start my car and get the "p" lock message and triangle. It allows me to drive it, I drive it 2 miles and stop. Full shutdown. Go to restart, it starts, and goes into ready but will not shift. It beeps the beeps of attempted shifting.

Dash symptoms:
Red triangle
"p" lock warning
(!)
VSC

Techstream symptoms:
Round 1 (before clear)
p3102
c1300
c1310
c1377
u0123
u0124
u0126
b1421
b1443
c2304

Round 2 (after clear, codes immediate)
p3102
c1310
b1421
c2304

Attempted fixes:
New 12v Battery
Jump started in addition to 12v battery
Pulled and waited on 7.5a fuse
Pulled neg cable for 2min
Jump wired 7.5a fuse to Blue #4 wire in harness
Checked all fuses under hood
Stepping on and off of parking brake a lot
Power on off a lot
Code reset w/ techstream.

Red herring:
When I attempt to restart the car, the door dinger and everything is functioning, attempt to start it, no success.THEN door dinger is gone, radio stops working, clock dies, no dome lights. I check the fuse box, the fuse is GONE, not there, missing. I put a spare into its place and all the above electrical start working again.

Red herring #2:
Previous owner claims to have replaced brake unit under hood. Clearly did a subpar job. Likely car has more history than told.

Help please.

 

Next thoughts.
Check/Replace Parking Control System Relay
Remove and reinstall parking actuator harness.
Replace all fuses that could be linked.

 

Let's add another clue.
The fuel gauge has 1 blinking bar on it. (no other bars present, it has more fuel than that)

Finally got the car towed to the house. My next step is going to be to check the connection on the trans ecu, any help on getting to this easily?

 

Now we're cooking!
Mileage, 175k.
Car seems to have lived its life on Hawaii, no corrosion anywhere obvious

Clean title, Aftermarket HV pack... BUT I bought it with a mis-colored, a bumper that had been removed and the lower grills messed up, and unsecured shrouding over the radiator, from an owner who was not above falsifying information.

I have gotten the "p" lock before, but pulling the 7.5 fixed it. Seemed like a bad battery was the culprit from leaving the door open.

Current thoughts, however the haz was receiving power w/o a fuse has stopped working. ( a fuse in the haz position was needed to get it to beep and recover the interior electronics. I had to use the "horn" fuse to put into its space, the "horn" is now open. -Does anyone know of anyway to gerry the "haz" circuit in an inconspicuous way w/o a fuse?

 

I either found an answer tonight or a rabbit hole that goes to the wrong place. Dissassembly of the dash to get the the trans ecu presented a pair of 12ga speaker wires running from the drivers side, spliced into the engine ecu harness.

Jiggling and manipulating these wires made the fuel gauge stop blinking and read correctly. Also allowed the buzzer and etc to function without a fuse in the haz spot.

The fat blue wire running next to the harness (stock looking wire) is spliced into.

 

Here's a new splash of information.
The previous owner bought the car from the dealer. It was a dealer car from 07-10. Previous owner claims they did not do any modifications, only replacing the HV and brake module. Monday I will be reaching out to the dealer to see if they have records of this speaker wire modification. Fingers crossed that the stars align and they have record of what and why that was done. It seems like a fair guess that whatever is being bypassed/changed is allowing the interior to function without the HAZ fuse.

The splice job splices into a green/aqua wire at either the Hybrid Vehicle Control ECU or the Engine Control Module, then heads into the driver side section up near the Power Source Control ECU or the Daytime Running Light Relay.

-What is steering you towards a brake control issue, I'm not seeing that in the fault codes. I understand though that the whole system is interlinked.

-Is it a fools errand to chase down this wiring job, I'm nervous/ suspicious that it may be a problem, but not THE problem.

 

I will try and get that this evening!
Off to the dealer to see if they have the service records.

 

Evening update time:
-Toyota dealer claimed it was illegal for them to tell me my car's service history.
-The toyota website mentioned by SFO indicates there's more to the cars story, starting in PD not Hawaii, but there's not any information on there beyond 1 oil change @8,000 miles.

Now for the fun:
-Digging through the dash I traced the speaker wire all the way through, It is connected back to itself and seemingly only bridging a 20ga black wire from the ecu.
-I found an aqua wire spliced into the harness from the steering control loom, it seemed to run into a wire sheath and into the certification ecu. BUT, further investigation revealed it was just sitting in the loom unconnected and appearing to never having been connected to anything (It is part of a 2 into 3 connection, where the 2 are still present and same colored).
-There's a green and a blue wire spliced together, these appear to be from a brake pedal sensor. These wires also appear to be simply bridging a black wire from this sensor.
-An identical blue wire (size and color) is present that does not go anywhere, just open.

I went through TechStream, but I'm unclear how to find INF'. Here's some screen shots from tonight.

 

Additionally attempted to remove the parking actuator wire from unit, couldn't get my hands in there well enough.

Current thoughts:
Wiring may have been from an interlock or blow and go of sorts? Could be using the brake pedal as a break for the starting system.
Trans ecu may be bad.
A break in the wires somewhere.

Still pondering:
The car still does not need a fuse in the HAZ spot for the buzzer to function.

Whats the next step in this diagnostic?

I don't see any trans ecu diagnostic procedures.
I don't know how to get the park actuator harness off, but it seem clean and tight.

 

I'll plug the computer back into the car this evening.

*The car starts, idles and does all the ICE things associated with it.
The car is run fairly hard. The underbody is fairly clean, the rocker panels not so much.

 

I Found this website to track the INF's
http://stuff.jaygroh.com/prius/Prius%20Info/Official%20Toyota%20Info/Repair%20Information/Repair%20Manual/HV%20-%20P112%20Hybrid%20Vehicle%20Control.pdf

-Update: Upon sitting in the car running tests, the ready light turned off. The car will no longer go into ready, sigh.

 

Here's tonights work on codes:
3102-581
-Harness
-Trans ECU
-HV ECU
-Power ECU

3102-598
-Harness
-Trans ECU
-HV ECU
-Power ECU

2304
-Shift control Assy
-Trans ECU
-Trans lock control
-Harness

2307
-Trans ECU
-Harness
-Parking lock motor.

From this, the only things that are present across the codes are a wiring harness/ connector problem and a Transmission ECU problem. Am I right in this thinking? or could they be triggering from different things?