2 wire sensor on brakebooster

does anyone know what the 2 wire sensor is on92 XJ power brake booster, i do have abs, not sure if it is related...

only picture i can find of the same style booster. the sensor is on the left side...
i was thinking of doing a WJ booster swap, but need to know what to do about the sensor.
thanks


also referenced here, http://www.naxja.org/forum/showthread.php?t=930846
no answer though...

well if you do the WJ booster and master swap plug the sensor wire into the new plug on the side of the new master cyl.. or drill a whole in the new booster

I would imagine your "brake" like will come on under the dash if that sensor is unplugged

well maybe i will try un-hooking the connector onthe current booster and see if everything still works, could just be a sensor for vacuum feedback to the ABS system...

only thing i could think of is maybe it reads vacuum, and if it gets below a certain reading your red brake light comes on, which is supposed to indicate a problem in the base brake system. in this case, not enough vacuum to the booster or the booster is leaking etc.

Wow, never seen that before.

Lemme go grab my 92 ABS system FSM supplement (I have no idea why I even bought this from someone, but I did) and see if it says anything about it.

Found it.

It's apparently a variable resistor sensor of some sort, it's shown in the diagram on page 135 as "pedal travel sensor (on brake booster)" in the 92/93 ABS subsystem FSM supplement book.

Other info:
"During an antilock stop, the brake pedal position is maintained within a controlled region by the pedal travel sensor and the pump/motor. The pTS has seven voltage steps. Once an antilock control cycle has been initiated, the CAB will activate the pump/motor when the PTS level increases one step and will turn off the pump/motor once original position is reached again."

"Vacuum booster / Master cylinder / Pedal Travel Sensor: the pedal travel sensor signals brake pedal position to the antilock CAB. The sensor signal is based on changes in electrical resistance. The resistance changes occur in steps generated by changes in brake pedal position. A resistance signal generated by changing brake pedal position will cause the CAB to run the antilock pump when necessary. The sensor is a plunger type, electrical switch mounted in the forward housing of the power brake booster. The sensor plunger is actuated by movement of the booster diaphragm plate. The tip on the sensor plunger is color coded. The tip must be matched to the color dot on the face of the brake booster front shell."

I learned something today... I had no idea any such thing existed.

kastein said:

Found it.

It's apparently a variable resistor sensor of some sort, it's shown in the diagram on page 135 as "pedal travel sensor (on brake booster)" in the 92/93 ABS subsystem FSM supplement book.
I learned something today... I had no idea any such thing existed.

Click to expand...

So, basically, it tells the computer when you are standing on the brake pedal and to please activate the antilock system and to turn the pump on. New to me, I have never seen this in any other vehicle.
Thanks for researching the answer.

Kastein, you always have the info i need, i dont know how.
that was along the lines of what i thought it did, i had never seen any other reference to it besides the naxja post i linked to and the picture i posted from pirate.

i dont really see how i could get this swap to work without the right booster, ie the factory 92 booster.... i am assuming if i put a hold in a new booster like the wj booster it would cause a vacuum leak...

I'm an FSM and parts catalog nerd :eyes:

I'd honestly never seen nor heard of such a thing. I'm not sure how you can get it into another booster, either, since it mentions that it has to be color coded to the booster and obviously a modified booster wouldn't be matched to it.

It's a resistive sensor with multiple steps, so it's not as simple as wiring it open or closed... hmmmm... I think most people would probably say screw it and disconnect the ABS system at that point. The 92 and later system can be disabled simply by unplugging the relays and fuses for it, so if you don't care about ABS that's the easy way out, I've got no idea how you could connect it to the newer booster to keep the ABS functioning.

I know it applies to the 92/93 ABS system since it's in the FSM supplement I have for those years, if I had to guess it also applies to the 94 system. I know they went dual diaphragm booster and changed the design of the ABS system in 95 so there's a good chance that sensor simply no longer exists after that point.

You may have to do some more changes to the ABS system to retain ABS and have a WJ booster. I do know the '96 XJ does not have that sensor with ABS as I own one.

kastein said:

I know it applies to the 92/93 ABS system since it's in the FSM supplement I have for those years, if I had to guess it also applies to the 94 system. I know they went dual diaphragm booster and changed the design of the ABS system in 95 so there's a good chance that sensor simply no longer exists after that point.

Click to expand...

My parts book for '94 shows it. The part number of the hydraulic control unit was the same in 92, 93, 94, it differs in 95 and 96.

the dual diaphragm booster didnt appear until 96 correct?
so to retain abs i am stuck with this system i think

It showed up in 95. 95/96 use one setup, then they redesigned the firewall (slightly, it doesn't affect the brake system really), pedal box, and most of the interior in 97 so that necessitated another set of brackets and stuff.

I was hoping there was an easy way to put a newer (95/96 or 97-01) master cyl on an earlier booster since I've got an 88 MJ with a super gross master cylinder, but it doesn't appear there is.

Why would you want to keep the old single diaphragm booster Ken? Go with either a WJ booster or a '95/'96 double diaphragm booster and call it a day. The modifications needed to the pedal rod are minimal and easy to do with a dremel and a little bit of OCD (of which you have in spades.)

I did a WJ booster in my 91, I agree it's not difficult.

Mostly I just want to put the bare minimum of effort into fixing the 88 MJ because it's getting stripped down to a bare chassis sometime soon to get a 5.9 V8, NV4500, NP241DLD, custom front axle, and 14 bolt rear swapped in, as well as (eventually) a late model interior, so any effort and parts expended on the current setup is wasted effort in the end.

And being 6'4", swapping brake boosters is approximately my least favorite project ever. Working under the dash... mutter mutter

kastein said:

And being 6'4", swapping brake boosters is approximately my least favorite project ever. Working under the dash... mutter mutter

Click to expand...

Remove the rear window first, that should make it easier.

ABS? pfft. My ABS pump is attached to the end of my leg. It's worked for years that way without fail.