BSM System Totally Dead - Troubleshooting Woes (2020 Tacoma)

I ran a new power wire from the connector behind the spare tire…..branched it off to both modules.
The harness was on back order so I made a repair.

 

Hi All! I had some time earlier today to take a look at the BSM system and learned more, however, no breakthroughs. I'll share what I learned and hopefully you can point me where to go from here.

As you can see from the attached pictures (checked with ignition "on" but engine not running), I am receiving battery voltage between pins 5 BLB (light green) and 10 BLGD (white/black) regardless of whether the BSM dash switch is on or off - My understanding is this is correct as this is how the module receives power whenever ignition is on.

Next I checked between pin 8 BSSW (grey) and 10 BLGD (white/black) and received battery voltage when the BSM dash switch is on, and close to 0V when the BSM dash switch is off. My understanding is this is also correct, as this is the voltage that tells the BSM LH module (master) to "turn on" and start communicating with the CAN bus.

As I mentioned previously, there is an issue with continuity of pin 3 BIND (yellow) between the engine bay EB5 connector and the BE1 connector under the rear bumper, however, from what was shared previously, my understanding is this wire serves to ground the 12V that flows through the BSM dash light, so it not working will prevent the green light on the BSN dash switch from turning on, however, shouldn't have any other impact. I jumped this previously between EB5 and BE1 with a temporary wire run along the side of the truck and nothing changed

My understanding from above is the LH (master) BSM bumper module is receiving power required to operate on the pins it should be

If power is good then the service manual says to replace the BSM module, however, I have tried 3 different modules (of which I am pretty confident at least one is good) with no change, so next I am thinking of an issue with CAN communication to the module (would make sense why the truck doesn't see it on Techstream at all)

Next I took a look at the voltages between the CAN pin 2 CA1P (black) and pin 7 CA1N (white) and pin 10 BLGD (white/black) and received some odd voltages of roughly 1V and roughly 2V. My understanding is this should be around 2.5V with 0.5V changes as modules talk on the network. Is this correct?

I know that 6 wires go into the J20 Junction Connector - Pins 6 (black) and 7 (white) ultimately run to CA1P and CA1N, and I can confirm continuity to the BSM module, so I know that wiring is good. The other pins form 2 strands of 2 wires that run to EB5 - Pins 1 (pink) and 2 (blue) and pins 3 (white) and 7 (white) connect to each other in J20. I checked continuity in EB5 between pins 1 (blue) and 11 (pink) and pins 22 (white) and 12 (white) (which I think should be looped when J20 end cap is installed), however, didn't get anything on either (is this an issue?)

Next I disconnected EB5 with ignition on and check the voltage of the CAN pins - Pin 1 was roughly 2.75V, Pin 22 was roughly 2.25V, and Pins 11 and 12 were 0V - When I reconnected EB5 and the J20 junction connector is installed (completing the two loops) then pins 11 and 12 go up to around 1V and 0.5V respectively. Seems like some voltage measured on 11 and 12 is coming from pins 1 and 22 when the J20 plug is installed.

I took a look at the first foot or so of the wiring coming from the J20 junction connector and didn't see anything concerning. I still don't know why I'm not able to get continuity between EB5 and an individual pin on the J20 connector (when the plug is removed)

My plan was to run a new 6-wire stand from the engine bay to the back of the truck to provide new CAN wires and the yellow pin 3 wire to the J20 connector and the pin 3 BIND connector on the master bumper module, however, I'm hoping to get some advice as running this wire will involve time, soldering, etc. and I don't want to do it until I am reasonably confident I'm barking up the right tree.

 

As your post is very long and detailed, I am going to comment within your post in BOLD. Some statements will be contradictory. Just like you trying to cover many possible outcomes.

Just some general comments:
Have you found the Network Gateway ECU? It is above the Glove Box, up very high. If I were to test (Ohm out) the circuit, I would start there and proceed down the line checking at each connector/junction for continuity. Access to the Network Gateway ECU requires the removal of the glove box.

With the truck off and the battery disconnected it might be possible to jumper the two CAN wires together at the Network Gateway disconnected connector and back track for continuity. I say with the battery disconnected because this truck has many wakeup features that could interrupt and confuse your progress. When checking for continuity, check also that the wires are not grounded anywhere too. They float and are never grounded, only terminated with 120 Ohm resisters

In your pictures I seem to be seeing an Electrolytic Capacitor. What's with that? Particularly the last picture where the two capacitor leads seem to be plugged in to the female connector.

Any possible chance this vehicle has had a leaky windshield or some other wetness in the driver's side kick panel area - IA3 is there, and the CAN goes right through it. So does the BIND wire. At this point I'd start there!!!

Picture of IA3 to follow: