Add Blind Spot Monitor - BSM w/CTA OEM retrofit in 3rd Gen Tacoma SR5

OEM Blind Spot Monitoring with Cross-Traffic Alert has successfully been installed in a 2023 SR5 Dual Cab, Long bed Tacoma.
Existing options included back-up (sonar) sensors and premium audio w/o separate amplifier.

Salvage vehicle parts included BSM Sensors 88162-04015 and CTA sounder 89747-52010.
New OEM parts included BSM switch 84470-04010 and Rear Bumper Harness 82169-04070.
Aftermarket parts included chrome signal mirrors w/BSM, Pre-painted bumper covers and bumper extensions.
Common parts included approximately 230 feet of 22awg stranded wire (in appropriate colors), 18 feet of plastic wire loom (3/8", HT black), approximately 25ea 8" black plastic wire ties.

Specialty parts included Sumitomo crimp terminals for connectors EB5, BE1 and BE2.
Male and female connectors are required, and excess quantities are recommended in order to learn how to make proper crimp connections and to correct mistakes.

The project was intended to look and perform as OEM. Therefore, necessary terminals w/wiring were added to connector EB5 in the engine bay junction box (EBJB) and connectors BE1 and BE2 at the rear bumper harness (RBH) connections.

The rear bumper harness was identified by examining another vehicle on the dealer lot at the time of the SR5 purchase. Using the harness (Toyota, $138.) saved significant time identifying, purchasing and assembling connectors.

A custom wiring harness between the EBJB and the RBH is approximately 18-1/2 feet of wire in 17 feet of plastic loom. Assembly was accomplished by stretching 11 wires between anchor points. Four of the wires make two twisted pairs for a CAN communication loop. The plastic loom is snapped over the taut wires and black electrical tape used to secure closure every 12 inches.

Exact wire length required for mating with BE1 and BE2 connectors are cut and appropriate terminals added with the harness/loom on the work bench.

The harness is routed rear to front adjacent to the main wire harness, but not secured.
Terminals, previously attached, are inserted into the existing connectors after removing seal plugs.

The new wire harness is drawn out and secured to the main harness using plastic wire ties.
At the rise under the EBJB, locate the new harness on the back of existing, away from the hot engine.

Using an 18" long 1/4" extension (or similar tool) compress the existing wiring to make room for the new to enter the EBJB. Trim wire lengths, add terminals and make appropriate connections to connector EB5. Secure the new harness to the existing with black wire ties.

Open (not remove) rear cab trim and install CTA sounder to existing wire and secure to body. Reattach rear cab trim panels.

Remove audio/display unit. Reach into the dash opening, locate the BSM switch connector and push through BSM switch opening. Engage plug to switch and push switch into switch opening. Reassemble audio/display, dash.

Remove door panels, remove outside mirrors. Install BSM mirrors (with direction signal).
Add green or blue wire from mirror connector (door/harness side), route through flex conduit to appropriate connector behind kick panel.

This should complete the BSM installation. If you added direction signal mirrors, they should be prewired on the SR5.

Addition to SR Tacomas and early 3rd gen without a CAN gateway likely will require additional effort.

Note1: Terminal locations at connector EB5 vary depending on OEM accessories. Details on terminal locations will follow in another post or a guide.

Note2: CAN wiring shown in the BSM wiring diagram is incomplete. A CAN loop is required. Refer to the CAN MPX wiring diagram.

Note3: Programming is not required. However, field of view adjustment is recommended.

More to follow.

Bill


BSM on RHS



BSM switch-at top, location for unused plug on other side of gray connector
(Front of dash is on left, we are looking down from radio/display)



EB5 with BSM added in EBJB

CTA Sounder location - unused plug awaits!



CTA sounder



Add wire to mirror BSM indicator!

Green wire for BSM indicator added to IC3.

 

Total cost?

 

Well, I was offered the SR5 to my spec with both Reverse Sonar (intuitive parking sensors) and BSM for only $10K over sticker price by Greer Toyota.
Found my spec SR5 - minus BSM at COX Burlington for less than $1K over sticker. Plus, a better color!
So, I was working against a savings of over $9K.
Actual cost of parts increased because the plastic bumper extensions were fitted for a newer (2024?) BSM module.
Parts to sell on eBay: OEM sonar bumper wiring harness, OEM R&L mirrors, OEM bumper extensions and OEM bumper covers.
I paid about $160 for the BSM modules, $25 for the sounder, $85 for the dash switch. Say $300.
OEM parts on eBay will bring close to aftermarket. Say I lose $150. That would be $450 on a bad day.
Plus, I got directional mirrors (that I really wanted) as a bonus.
My time? Priceless!

 

My 2023 SR5 came with BSM w/ cross traffic alert but does not have the reverse parking sonar. Would it be possible to add the parking sonar? Would I need the same bumper harness that you purchased?

 

Yes, it is possible to add the intuitive parking sensors.
See what you have to begin. I'd start by checking for existing wiring in the dash to the clearance warning ECU module and the "cancel switch".
If present, the plug for the switch will likely be secured in a dummy socket in the vicinity of the switch location.
If you find the existing plug/ECU connector, you are ahead of the game.
Next, research parts availability to complete the project.
New parts are cost prohibitive. If you can get the cooperation of your local used auto parts yard, the retrofit could be a piece of cake.
You will need the clearance warning ECU module in the dash, clearance warning buzzer, cancel switch, four ultra-sonic sensors in the bumper and interconnecting wire.
You may want to use bumper covers with holes rather than cutting the irregular shapes required for the sensors.
Wire is 22awg, stranded. Wire is no big deal, but connectors are by Sumitomo. Terminals require special care, so you may want to use the Rear Bumper Harness 82169-04070.
Only three wires are required from the engine compartment junction box to the RH ultrasonic sensor, which are then connected in series.
Keep us posted on your progress.

Bill

PS: Clearance ECU 89340-04020 is available on eBay but check your dash for the connector. The connector is a critical item.
Aftermarket sensors and associated connectors are dirt cheap, so a custom bumper harness may be a reasonable alternative.

 

Bill-

Thanks for the information. Would you happen to know where in the dash the clearance ECU would be located so I can check for the connector? Also, where the clearance warning buzzer is mounted so I can check for that connector? I’m about to install a Kicker Key behind the head unit, so it would be a good time to check for the connectors.
Do you have the part #’s for the clearance warning buzzer and the cancel switch?

 

The clearance ECU location should be visible, slightly lower/right, when you peer into the head unit space.
If the plug is present, it will likely be secured to the wiring harness or wrapped in foam or both.
The clearance sounder is below the instrument cluster, I think.
Recommend you search eBay to see the parts and view the connector socket.

You will also want to review the service manual available on this site. Applies to early 3rd gen but still good for all but the finest detail/differences.

While the head unit is out, use a light and mirror to look directly below. The plug for the Clearance Cancel Switch should be plugged into a dummy connector molded into the plastic trim.

 

Wow you pulled off what most said was near impossible. Amazing!!

 

Thanks.
It took a bit of research and study, but it is quite doable for SR5 and up as they are factory programmed for BSM and IPS (intuitive parking sensors).
SR may be another issue. But I'd like to see one done. If anyone near central Virginia would like to give it a try, I'd lend a hand with crimping terminals, etc.

 

@Bill400
Congratulations:
I like your labeling of the connectors - I do the same so I do not have to repeat location research twice or more while making changes.

I do not understand the "CAN loop" statement. In the multiplex/CAN schematic, as well as the BSM schematic I can only find the Vehicle CAN going to the Left BSM module and then the data connection between the two BSM units on pins 1&6 in a Series connection; whether this is CAN or not, I suspect but am not positive. Was the CAN necessary for the BSM to properly work? Also if you did try it without CAN what were the difficulties? I am only trying to understand the vehicle, or rather the thinking of the Toyota engineers.

Have attached the MUX schematic I have.

Good, no Great job.

Extra Credit:
How would you like to try a correction to the speedometer and Cruise control speed for a tire size change? I see this as a circuit addition between the wheel speed sensors and the Skid Control ECU to modify the hertz of the signal. This of course is nothing a for profit company should ever attempt to put on the market, but I would be more than happy to make a change to my vehicle.

 

@Toycoma2021
CAN works at radio frequency. It is subject to RADAR-like reflections within the wire.
A CAN bus is usually seen as a pair of wires, one high and one low. In practice, they are twisted to negate outside interference.
The CAN bus may be quite long and requires resistors at each end to dampen reflections.
Control modules are connected to the bus by branches. The branches are required to be short, usually 18" or less, to avoid reflections.
Since the CAN bus for the BSM is located in the engine compartment junction box (ECJB), the "branch" to the BSM would be 18 feet long.
The reflections resulting from the 18Ft branch would be seen as messages and drive the CAN network crazy.
Toyota's solution is to "loop" the CAN bus from the ECJB to the bumper harness and back to the ECJB. The branch to the BSM module can then be about 18 inches.
Connection between the BSM modules is a separate bus, may be CAN but I suspect that it is LIN.

Print and splice the multiplex diagram for easier viewing. The BSM diagram merges the loop and branch, which is misleading.
The multiplex diagram features the multiplex module.
Toyota uses the multiplex module to create different CAN buses, another technique to avoid reflections.

I appreciate your correction device. However, the Tacoma ECM should be capable of programming for different tire sizes. Has no one done this?

 

I am familiar with CAN, a past vehicle (GM) did just what you describe with the length issue. They routed the CAN to each module directly and then back out, if you removed a module it broke the CAN circuit, i.e. nothing much worked. If one wished to eliminate an entertainment or monitoring module you had to jumper the CAN Bus at the module connector to continue the circuit to the remaining modules. Not to mention that all modules were inventoried by a master module and if one were missing errors would set.

I forgot to mention I thought it was great you mentioned that the CAN wires should be twisted. The CAN Bus is “differential amplifier” based, only what is different on the two wires is amplified and the rest (noise) is suppressed by the diff amp. They are twisted so any outside noise is equally impressed upon both wires and can be cancelled out by the diff amps. A very popular application was the original telephone wires which can run for miles operates on the same principle and picked up much noise in their journey to your house or business.

I’m guessing here, but it looks like J20 is the CAN junction I now remember seeing at the rear of the vehicle you are referring to. There is one like it I have seen just in front of the battery and behind the driver’s headlight.

The LIN circuits on this vehicle is one wire, the LIN circuits I have explored a bit are the alternator and the window controls.

A device by Hypertech corrects the speedometer, but not the cruise control. My guess is Toyota does not wish to take any responsibility for any customer changes to the vehicle including tire size.

Added 1 Nov 2024: Hypertech now corrects for cruise control.

 

Yes. J20 is a CAN junction. I did not add a J connector adjacent to the bumper harness. Rather, I added the twisted pairs to the BE connector, saving a crimped connector.
The decision was to avoid a potential point of reflection.
EB5: The subject CAN bus is present both ends of the EB5 connector on pins #1/#12 and #11/#22.
I lifted pins #11/#22 and added them to a new connector I call EB5A. Two additional wires from EB5A land on the original EB5 locations.
EB5A provides a break in the existing can bus to allow extension the loop to the rear bumper.
The loop (two twisted pairs) from the BSM go to EB5A to complete the CAN loop.

The GM system designer could do as he wished using CAN but the description sounds a bit like a token ring.

LIN may use a dedicated ground. But that was a guess. Inter BS module comm may be a dedicated CAN bus. Don't know for sure.

Do you know the character of the wheel speed sensors? A typical variable reluctor, magnetic pickup increases voltage and frequency simultaneously with speed.
Can you confirm the maximum volts and frequency? Typical output would be helpful.

 

The GM CAN seems theoretically better to me, I'll explain: A 120 Ohm impedance wire pair, which is what the CAN wiring is designed to be, when terminated at each end with 120 Ohm resisters should be reasonably terminated and reflection free. My thought is that it is the "stubs" that create the reflections, keep the stubs short and there may be less reflections. Toyota has provided junctions where the CAN can be easily accessed for breaking apart each CAN section for testing but increasing the stub length. While the GM stub is just a short trace on a PCB. My 2006/2009 GM was a pain to test, often having to disassemble whole sections of the vehicle to get to the modules to access the wiring. It is good to know that if I have any problems disassemble will not be necessary.

Yup, without a scope or a decent factory description we are both in the dark.

Again, I'm in the dark. My plan was to get a hold of a Skid Control ECM at some point and discover just what IC chip was receiving the wheel speed sensors signal and learn about it from that perspective; even using the same chip as Toyota was using as my input to whatever I put together to modify the signal for different size tires. My only requirement was to have the access point or selector switch in an easy to access location in the vehicle. The Skid Control ECM module I believe is behind the glove box. This requires removing the lower passenger side air bag, the glove compartment and IIRC loosening some of the center console to gain access. Pretty easy but see no reason to do so with each tire change.

My original thoughts were to change the number of magnets on the wheel hubs, but that would not offer enough resolution. Let's say there are 20 magnets on the current hubs and by adding one more that would change the speed by ~5% - I dropped that idea pretty fast after that. A place in the UK was willing to look into it but either they or their supplier required a large run to manufacture the magnets and that would only get close to correcting the speed.

There are two speed sensors:
RR & RF 89542-04020
LR & LF

$17 89543-04020 ABS Sensor Compatible with Toyota Tacoma(05-20), 4Runner(03-20), FJ Cruiser(07-14), Land Cruiser(08-20), Lexus GX460 (10-20), GX470(03-09), LX570 OEM Replacement ABS Wheel Speed Sensor

89543-04020

 

Update to add BSM wiring pin-out for EB5 and BE2.
Attached.

 

I am brand new to the world of Tacomas. My son has a 21 3rd gen. I honestly am not sure whether it is an SR or SR5 but I was looking into adding some of this tech for him. Odd he has things like LDA and collision avoidance along with Radar Cruise, but not parking assist or BSM. I really would like to add park assist and have found the part numbers for the modules but the harness is confusing me. If I look under the back of his truck, there is no BE1 connector. I find it hard to believe Toyota would have different harnesses for different trims lines. I am a long time Ford truck person and I know they put the same harness if all of their trucks regardless of finished trim line. But maybe just the way it is....

 

Sorry for the late response ... just saw your post.
Apparently, all 3rd Gen Tacos have "safety features" LDA and collision avoidance along with Radar Cruise.

You are correct: Toyota saves a ton of wire by customizing wiring harnesses for every conceivable accessory variation.
Actually, I think that the variations are part of the Toyota marketing strategy to make the post-factory addition of OEM options as difficult as possible.

Your photo of the SR bumper harness is revealing. No BE1 connector and bare minimum wiring to BE2.
The easiest way to retrofit OEM rear parking sensors and BSM/CTA to an SR would be to obtain the wiring harness from a high option Taco salvage vehicle.
That would include EB5 in the engine bay to and including the rear bumper harness.
Alternatively, you can make a supplemental harness (about 14 wires in plastic loom), add terminals and BE1 connector.
Also, purchase the rear bumper harness from the same salvage vehicle or fabricate.

 

Yes and the write up was A+++++

 

Thanks TacomaGuy,
I would encourage folks to be adventurous and do the upgrades that they want.
Where there is a will, there is a way.

The BSM is a handy feature, but the CTA is a lifesaver!
If anyone needs help or has questions, join in.
If you happen the be near central Virginia, we can meet for coffee and talk in person.
best regards,
Bill

 

More info: