Is there a way to trigger ABS actuator to combat spongy breakes? (1 Viewer)

[RedTacoma]

Truck info: 1994 LC with ABS
So after some brake work (Caliper replacement with pads) I had spongy brakes. Wasted good amount of brake fluid trying to bleed them. I suspected that Air was trapped in ABS actuator but short of buying the SST tool or driving on Ice I did not see a way to trigger ABS.
While doing my front axle rebuild I installed my ABS sensor incorrectly which had resulted in ABS kicking in while descending steep grade. That had fixed sponge brakes immediately.

My question is how I can cycle actuator with out driving and with out SST tool?

Toyota lists 3 pieces for sst

(a) Connect the actuator checker (SST) to the actuator,
control relay and body side wire harness through the
sub-wire harness C (SST) and E (SST), as shown.
SST 09990-00150, 09990-00200, 09990-00210

Can somebody shed some light as how the tool works ? Voltages? Connectors ? So I can built my own.

I always trigger ABS on my other car after the brake work. But there is a "paperclip" override to do that. I can not find anything on how that can be done on LC. Any idea...?

 

[scrowley]

I would love this info right now.......no body ever replied.....

 

[ToddD]

Subscribed. I don't need to do this but it would be awesome if there was a way. Hopefully something comes up in this thread.

 

[zzdudaka]

Subscribed. Mine was pulling to right and a little soft. Turns out some idiot installed inner drivers pad wrong!. Flushed entire system while i had truck up. Still soft pedal, pedal holds with ignition off but slowly goes to floor with ign on, never seen a vehicle do that before. I am thinking perhaps master cylinder seals rather than abs, but in for info on this.

 

[firetruck41]

Pg 133-137 of the LX450 EWD has the wiring diagram and description of operation for the ABS system. Someone a little smarter than me could figure out how to activate the ABS actuator. If the ABS were a $5 part, I'd try sending 12v to position 3 and/or 4 of connector A5 at the actuator, then if I blew it up, I'd only be out $5...

EDIT:
Strike that: looking at the diagram of the SST, if the drawings of the connectors are correct, it taps into the A6 connector on the actuator...

 

[SUMOTOY]

SUMOTOY ABS Solenoid-Cycling mod

Most new cars/trucks have a ABS cycle mode in the OBD adaptation tables to cycle ABS solenoids. Prior to this feature, back in the 90's I made an 'ABS Solenoid-Cycler' with a 3 channel Bosch system that looks quite similar to the 93>80 series 3 channel ABS systems. I have modded a 3 channel Bosch actuator using the same method the 80 EWD identifies as valid.

DISCLAIMER AND WARNING
I am reading the 93 EWD and have not tried this method on the 80. I have not tried this method, nor do I recommend messing with or modifying ABS electrical systems without full knowledge that it can fail by any non-factory test part. My reference is the 1993 Landcruiser EWD (page 13) without revision or assumption it's correct or wrong. Whew.

HOW TO DIY SOLENOID ACTUATION ACCORDING TO THE 93 EWD:
I made this so you *must* have the EWD to reference for attempting this mod. If it sounds like another language to you, good, you shouldn't mess with it....

The abs actuator contains the solenoids. EWD page 13 shows that these solenoids are always powered, and are 'ground activated' solenoids by the ABS ECU. Pull ABS relay and Disconnect the 'F' (ground) connector from the ABS ECU. Pull connector G and H at the actuator. Apply 12v power to connector G position 4 at the actuator (power is now 'hot' to the 3 solenoids - 2 front and single rear). On Connector H at the ABS actuator, with the respective brake bleeder screw open Cycle to GROUND respectively: Pin 1 (Solenoid ground Front Right), Pin 13 (Solenoid ground Front Left) and Pin 3 (Solenoid rear). How to cycle? Well, that's up to those really looking to do this procedure. I suspect a modified 5pin relay (87 and 87a) can be made to work for this, but tapping a momentary contact switch to ground would likely do the trick.

This will cycle the pintle solenoids at the actuator, which are known to trap air bubbles if the brake master cylinder resevoir empties during brake service. IME, a pressure bleeder on the 80 resevoir tends to make any 'cycling' of the solenoids unnecessary.

HTH, and don't do this because it can be done.

Scott J
94 FZJ80 Supercharged

 

[kirkm76]

I did the take it to a dirt road and slam on the brakes method to purge mine.

 

[DARKNESS]

Reviving an old thread, but I just used a version of the method SUMOTOY proposed and it worked great. I just replaced all my calipers and lines and allowed the master to go dry in the process so I had a ton of air in the system. I bench bled the master and bled the lines by pumping the brakes but they were still really spongy.

To get the remaining air I jumped both ABS relays to provide power to the solenoids and the pump. Then I disconnected the gray and black connectors at the ABS unit. Finally I used a wire to ground each of the solenoids at the gray connector on the abs unit and plugged the black connector back in repeatedly to activate the system.

I then bled the system again and got a significant amount more air and a much much firmer pedal. Most of the air came out of the LSPV, though some came out of both front calipers too. Not sure how this compares to actually activating the ABS on the road, but it worked for me.

 

[86tuning]

While driving ~20mph you can put two tires onto a dirt shoulder and use the brakes moderately hard, the ABS will actuate on the low traction side. Then cross the other side and do the same with the other two tires. Obviously don't do this on a road with traffic.

 

[Delancy]

While driving ~20mph you can put two tires onto a dirt shoulder and use the brakes moderately hard, the ABS will actuate on the low traction side. Then cross the other side and do the same with the other two tires. Obviously don't do this on a road with traffic.

Is is possible that having too much air in the ABS system, for lack of better, could negate it's ability to engage?

Mine will not, even at 30mph....which stained my drawers.

Spoke with an old school Lexus tech yesterday and he claimed they've never had any issues with the LXs, nor had reason to engage the pump to bleed.

 

[AppleTech]

What does this sound like? I've got it wired up according to SUMOTOY's directions and reviewing my EWD, and I'm getting a click at the solenoids but nothing like the "bang" I'm used to hearing when ABS is being actuated. I've definitely got air in there...

Here's what it sounds like for me:


Any help would be appreciated!

Thanks,
Phil

 

[blkprj80]

What if you actuate it with the brake pedal depressed hard?
I think the noise you're looking for happens under brake pressure, and would involve clicking that switch at 10 Hz or so.

 

[trials935]

What if you you put your 80 with non locking diffs on a lift with 2 wheels on the same side on the ground and the 2 wheels on the other side are elevated, and you put it in gear, and stepped on the brakes while feathering the throttle to keep the 2 elevated wheels spinning, wouldn't the abs activate on the side that was on the ground not spinning?

 

[blkprj80]

What if you you put your 80 with non locking diffs on a lift with 2 wheels on the same side on the ground and the 2 wheels on the other side are elevated, and you put it in gear, and stepped on the brakes while feathering the throttle to keep the 2 elevated wheels spinning, wouldn't the abs activate on the side that was on the ground?

I think you should at least shoot a video if you're going to do this. I'd be afraid the ABS wheels would transfer the torque to the other side, and you'd probably have a big problem shortly thereafter. Bring clean undies.

It might work though.

 

[AppleTech]

Yeah I'm starting to lean towards just deleting ABS. This truck is going to be trail only in a few months and I'm OK living with no ABS on road as I've driven non-ABS cars before. I think that honestly these trucks may stop safer with no ABS than with the poorly functioning one they have.

 

[trials935]

The open diffs are not controlled by an Ecu like more modern 4 wheel drives, so no torque issues should happen, we did this method on 2 wheel drive Porsches with no problems. (Still don't know if I would try it though)

 

[-Spike-]

What if you you put your 80 with non locking diffs on a lift with 2 wheels on the same side on the ground and the 2 wheels on the other side are elevated, and you put it in gear, and stepped on the brakes while feathering the throttle to keep the 2 elevated wheels spinning, wouldn't the abs activate on the side that was on the ground not spinning?

I think you should at least shoot a video if you're going to do this. I'd be afraid the ABS wheels would transfer the torque to the other side, and you'd probably have a big problem shortly thereafter. Bring clean undies.

It might work though.

The open diffs are not controlled by an Ecu like more modern 4 wheel drives, so no torque issues should happen, we did this method on 2 wheel drive Porsches with no problems. (Still don't know if I would try it though)

Oh man, I want the video of this too. Locking the brakes on the spinning, elevated wheels is going to put all the power to the opposite wheels- the ones on the ground. That's how open diffs work. It will allow one wheel to spin. It will force one wheel to spin. If that wheel is on the ground, the car's gonna move. Hilarity will ensue. For the viewers of the video, anyway, probably not so much for the poor guy who got talked into doing this.

In all likelihood the car wouldn't move, since the guy performing this stunt wouldn't be hard on the accelerator, but it might be just enough to pop the car off the jackstands or whatever.

 

[cartercd]

It would be very helpful if someone who has done this can provide more specific instructions / photos of:

-Location of ABS ECU. I believe this is the silver box in the left side footwell.
-How to disconnect the 'F' (ground) connector from the ABS ECU. Is this its own connector or do you need to pull an individual wire from the socket?
-Distinguish between the G and H connector at the actuator (one is grey and one is black, but I don't know which is which)
-Where is position 4 at connector G?
-Where are positions 1, 3, and 13 at connector H?

If I can get some clarity on these I am happy to do a write-up with pics to make this easier in the future.

 

[cartercd]

I'm trying to assemble a very clear set of instructions for this. I believe the diagram below reflects how the ABS actuator pins need to be powered/grounded to cycle the solenoids. A few questions:

• Is it necessary to do anything at the ABS ECU or Relay, or can everything be done at the ABS actuator as shown in picture?
• Is it necessary to open the respective bleeder screws when activating the solenoids (in which case instead of grounding all 3 solenoids simultaneously as shown below you would want to do one at a time)

 

[Toph]

So, I was just trying to diag a possible stuck/sticky caliper so I set the cruiser on four jack stands two on each axle. Each wheel only one maybe two inches off the ground. Had my helper shift it from park to drive. The wheels spooled up as they would. When he depressed the pedal to slow the wheels is activated the abs immediately. I tested it a couple more times and each time it activated the abs module.

I’m gonna replace my master and get to the bleeding using the abs activation method we stumbled upon. I’ll report back with an update.