Help! Dreaded Brake Indicator Light on!

[J33Pfan]

2002 Lib V6 4WD

It all started when a FR Brake Hose blew out. Parts were replaced. Everything was bled out many times.

What turns the Brake light on in the Dash? ABS Sensor, E brake, Fluid Level... What am I missing?? Is there a brake equalizer or a Pressure sensor to check?

The Brakes work fine now but the Brake light on dash comes on right away!
I think the rear ABS/Speedometer wire & sensor are fine as the Speedo works fine. The ABS light has always been on.


thanks

 

[Billwill]

Speedometer on the early models is run by the sensor on the rear diff.

The brake switch has three switches on it..one for brake lamps at the rear, one for Cruise Control and one for ABS and also cross-checks with the pressure switch on the Master Cylinder.

I would suspect the switch on the Master cylinder is not sending confirmation to the BCM that it is working. There is also a resistor across this Master Cylinder switch...about 1k Ohms I think....not shown in the wiring diagrams.

So if you replace the master cylinder reservoir make sure this switch is there and has the resistor across it.

The brake switch assembly can not be re-fitted once removed so do any testing of it while it is in place or buy a new one and fit it.

Download the 2002 Jeep KJ Service Manual here...will give you some Theory of how the brakes work and section 8W has the wiring diagrams. Some wires may have been damaged fixing the brake hose problem or the Master Cylinder may have a problem.

Jeep KJ Manuals:Index of /manuals/Jeep/KJ

 

[LibertyTC]

With an ABS light on a C code will be present.
Have some one with a capable shop scanner pull the code/s, and see what's up.

 

[tjkj2002]

No brake pressure sensor on a KJ's master,only a fluid level sensor.

Things that turn on the brake light in the IC.....................

1-low brake fluid(level sensor)
2-bad level sensor
3-any ABS codes(if you have ABS)
4 parking brake switch

You will need a high end scanner to access the BCM and ABS modules to check operation of the brake switch and any codes in the systems.

 

[J33Pfan]

Speedometer on the early models is run by the sensor on the rear diff.

The brake switch has three switches on it..one for brake lamps at the rear, one for Cruise Control and one for ABS and also cross-checks with the pressure switch on the Master Cylinder.

I would suspect the switch on the Master cylinder is not sending confirmation to the BCM that it is working. There is also a resistor across this Master Cylinder switch...about 1k Ohms I think....not shown in the wiring diagrams.

So if you replace the master cylinder reservoir make sure this switch is there and has the resistor across it.

The brake switch assembly can not be re-fitted once removed so do any testing of it while it is in place or buy a new one and fit it.

Download the 2002 Jeep KJ Service Manual here...will give you some Theory of how the brakes work and section 8W has the wiring diagrams. Some wires may have been damaged fixing the brake hose problem or the Master Cylinder may have a problem.

Jeep KJ Manuals:Index of /manuals/Jeep/KJ

Ok, Thanks Bill! SO my problem is that the Dash Brake light stays on now even though the brake system is repaired & Bleed. The MC only has a Fluid Level Switch. I was reading the manual and noticed the ABS system can store a code which causes the Brake light to come on. So I guess I'll need the ABS system to get scanned. What does that cost??

 

[J33Pfan]

No brake pressure sensor on a KJ's master,only a fluid level sensor.

Things that turn on the brake light in the IC.....................

1-low brake fluid(level sensor)
2-bad level sensor
3-any ABS codes(if you have ABS)
4 parking brake switch

You will need a high end scanner to access the BCM and ABS modules to check operation of the brake switch and any codes in the systems.

OK,Thanks! Ill check the park brake switch -though the ABS is always on but it hasnt caused the Dash brake light to stay on in the past but yes it could be the problem now.

About what does it cost to get the ABS Scanned?.

A few months back the dash brake light came on when the speed sensor wires broke on the rear axle. that repair is still good. maybe a #5 on your list.

 

[tjkj2002]

OK,Thanks! Ill check the park brake switch -though the ABS is always on but it hasnt caused the Dash brake light to stay on in the past but yes it could be the problem now.

About what does it cost to get the ABS Scanned?.

A few months back the dash brake light came on when the speed sensor wires broke on the rear axle. that repair is still good. maybe a #5 on your list.

Your KJ uses a 3 channel ABS system and the rear ABS sensor is also the rear WSS that operates the speedo.So any issue with that rear sensor will make the ABS not function and turn on the brake on also.

 

[Billwill]

No brake pressure sensor on a KJ's master,only a fluid level sensor.

Things that turn on the brake light in the IC.....................

1-low brake fluid(level sensor)
2-bad level sensor
3-any ABS codes(if you have ABS)
4 parking brake switch

You will need a high end scanner to access the BCM and ABS modules to check operation of the brake switch and any codes in the systems.

Yeah my bad...the switch on the reservoir is for fluid level. I have been trying to find the post on Lost regarding that switch and the resistor mentioned but that was long ago and my brain is fading rapidly!

There is however a Brake Pressure Switch which would seem to be part of the Controller Antilock Brake Module. I do not have ABS so I cannot follow this up and likewise without ABS my speedometer works only from the sensor on the rear-diff.:emotions34:

 

[J33Pfan]

Help!

Brake light is still on. ABS Light is off now I cant get an Inspection till its fixed!

Im going to recheck the Ebrake wiring and the MC Level Switch.
I couldnt find a schematic. Any help to get this light corrected would be appreciated.

thanks!

 

[J33Pfan]

Praise the Lord!

Looks like the New Reservoir Level Indicator doesnt have the same resistance as the old one. I connected an led light to the connector and the BRAKE LIGHT went out.
I have to buy the special E7 star socket to RnR the Reservoir.
(does anybody know what resistor I can use to delete this Level Switch?)
Thanks Everybody!

 

[Billwill]

Praise the Lord!

Looks like the New Reservoir Level Indicator doesnt have the same resistance as the old one. I connected an led light to the connector and the BRAKE LIGHT went out.
I have to buy the special E7 star socket to RnR the Reservoir.
(does anybody know what resistor I can use to delete this Level Switch?)
Thanks Everybody!

I will try find the old post on this resistor.

Definitely think that this was a 1 K Ohm resistor...did not replace the Level Sensor but was in parallel to it if I remember correctly.