Brake and Rear ABS lights on

[jermil01]

Replaced the VSS today to see if that would correct the problem, but no luck both lights are still on. Kept looking and finally found the self test connector for the RABS it was exactly where it was supposed to be in the diagram, guess I should have opened my eyes.. So if understand the instructions correctly, I need to turn the key on, ground then unground the wire and count the flashes. The the key need to be in the run position?



I'm thinking I may have a problem with my tone ring but I'll wait to see what the codes say.

[jermil01]

Ok, grounded the connector and was able to pull the codes or code, it was 4 quick flashes that kept repeating.

[El Kabong]

Was there a long flash at the end, or only 4 short flashes? I don't know if it matters, but on the 90 the instructions say to pull the codes with the engine running. On mine it ended with a long flash like the instructions described. Maybe that's just different in 92.

So on the 92 the test connector is on the passenger side near the glovebox? In that pic it looks like the wire is still black with an orange tracer. Is that correct? Can you get a pic from a little further back to include some surrounding features?

[jermil01]

No long flash at the end just 4 quick flashes that repeated over and over..I dug around some more in Steve's album and found this looks like a code 4 is RABS valve switch closed...so I'm assuming that needs to be replaced.



Yes the connector is right under the glove box on the far right side.. I you find the PSOM connector and go left its right there the wire is the same as the earlier one black with the orange tracer.

Originally Posted by El Kabong

Was there a long flash at the end, or only 4 short flashes? I don't know if it matters, but on the 90 the instructions say to pull the codes with the engine running. On mine it ended with a long flash like the instructions described. Maybe that's just different in 92.

So on the 92 the test connector is on the passenger side near the glovebox? In that pic it looks like the wire is still black with an orange tracer. Is that correct? Can you get a pic from a little further back to include some surrounding features?

[El Kabong]

There's more testing. I'll see what I can find for a code 4.

[miesk5]

yo!
RABS Diagnosis; except 93-96 (click NEXT to View more pages)
Source: by Jem270 at SuperMotors.net
Flashed 4 Times troubleshooting begins on File 49 of 56
-
RABS Valve & Yellow Warning Light Location Diagram in 90-92 Bronco & 90-96 F Series
Source: by Steve83

[jermil01]

Thanks guys.

miesk, that was helpful but it looks like either way it is the valve or a short somewhere. It's pouring outside right now, so l'll have to test some more after it stops.

Originally Posted by El Kabong

There's more testing. I'll see what I can find for a code 4.

Originally Posted by miesk5

yo!
RABS Diagnosis; except 93-96 (click NEXT to View more pages)
Source: by Jem270 at SuperMotors.net
Flashed 4 Times troubleshooting begins on File 49 of 56
-
RABS Valve & Yellow Warning Light Location Diagram in 90-92 Bronco & 90-96 F Series
Source: by Steve83

[El Kabong]

Edit -I just saw Miesk's link, but I already typed this , so I'm gonna leave it.

The manual lists some other things to check before following the code tests. I know you've already checked some of these, but I'll list them all to be complete for others later. The tests for 4 flashes start with 4a below.

From the 1990 Ford Truck Shop Manual:

Test C
Yellow ANTILOCK light On and
Red BRAKE Light On

C1 -Low brake fluid

Brake fluid level ok = Go to test C2
Brake fluid level low = Check for fluid leaks & repair. Fill system

C2 -Master cylinder float -Check float for buoyancy
1- Remove cap from master cylinder.
2-Using a clean steel implement, push down on float in resevoir.

Float moves down = Go to test C3
FLoat does not move down (Sits at the bottom of the resevoir) = Replace master cylinder resevoir.

C3 -Diode/resistor element -Check for proper functioning of the diode/resistor element.
1- Turn ignition key to the on position.
2- Check parking brake & release if applied.

Both ANTILOCK & BRAKE warning lamps go off = Replace RABS diode/resistor element.
Both ANTILOCK & BRAKE warning lamps stay on = Go to test C4.

C4 -Diode resistor element continued -Continue to check for proper functioning of the diode/resistor element.
1- Remove the parking brake switch & the diesel low vacuum switch, if so equipped.
Both ANTILOCK & BRAKE warning lamps go off = Replace RABS diode/resistor element.
Both ANTILOCK & BRAKE warning lamps stay on = Go to test C5

C5 -Antilock valve switch
-Obtain the flashout code as described in Diagnonsis & Testing in this section.

Flashout code is obtained = Refer to Flashout Codes Charts
ANTILOCK & BRAKE warning lamps stay on steady = Go to test C6

C6 -Master cylinder switch
-Check for the proper functioning of the master cylinder level indicator switch.

1- Remove the connector from the master cylinder.
2- COnnect a jumper wire between the 2 purple/white wires in the connector.
3- Turn the ignition key to the on position.

ANTILOCK & BRAKE warning lamps stay on = Go to test C7
ANTILOCK & BRAKE warning lamps go off = Replace the master cylinder resevoir.

C7 -Brake Light Wiring
-Check for shorts in brake light wiring.
1- Disconnect module harness connector from module
2- Turn ignition key to the on position.

Antilock light goes off & Brake light stays on = Check for short to ground in the 977 circuit. Refer to wiring diagram in this section.
Both ANTILOCK & BRAKE warning lamps go off = Replace module.

Flashout Code 4
Yellow REAR ANTILOCK Light Flashes 4 Times
Red Brake Warning Light Illuminated
RABS Valve Switch Closed

4a -Check for closed RABS valve switch
1-Disconnect RABS valve harness connector from valve connector.
2- Place ohmmeter on th 20k ohms scale.
3-Check resistance between valve connector switch pin & valve body.

Valve connector -Pin View
. . . . . . . . . . . . . . . .O
Valve switch pin ---O . . .O
. . . . . . . . . . . . . . . .O

Resistance is greater than 10k ohms = Go to test 4b.
Resistance is less than 10k ohms = Replace RABS valve

4b Check for short between RABS ground switch & valve ground lead
1- Set the ohmmeter on 20k ohm scale.
2- Check resistance between the valve connector switch pin and valve solenoid ground pin.

Valve connector -Pin View
. . . . . . . . . . . . . . . .O
Valve switch pin ---O . . .O
. . . . . . . . . . . . . . . .O--- Valve solenoid ground pin

Resistance is greater than 10k ohms = Go to test 4c.
Resistance is less than 10k ohms = Replace RABS valve

4c Check for rabs valve switch wire shorted to ground or module
1-Disconnect battery.
2- Set the ohmmeter on the 200k ohm scale.
3- Dosconnect the module harness from the module.
4- Check the resistance between harness connector pin 6 and chassis ground.

Module harness connector -Pin view

14 13 12 . . . . . . 11 10 9
O . O .O . . . . . . .O . O O

O . O .O . O .O . O .O . O
8 . 7 . 6 . 5 . 4 . 3 . 2 . 1


Resistance is greater than 100k ohms = Replace computer module.
Resistance is less than 100k ohms = Repair short in 535 circuit, valve switch wire from valve to computer module.

[jermil01]

For those interested, here is another shot of the test connector.



And the RABS module behind the glove box



So I got out my meter and realized that I don't understand how to read the ohm scale, can you guyst take a look at this and see if I have it on the correct setting:



when I perform the first test (below) with this setting, my meter reads halfway between the 10 and the 0, I think is 50K ohms, I'm not sure though:

Quote:
4a -Check for closed RABS valve switch
1-Disconnect RABS valve harness connector from valve connector.
2- Place ohmmeter on th 20k ohms scale.
3-Check resistance between valve connector switch pin & valve body.

Valve connector -Pin View
. . . . . . . . . . . . . . . .O
Valve switch pin ---O . . .O
. . . . . . . . . . . . . . . .O

Resistance is greater than 10k ohms = Go to test 4b.
Resistance is less than 10k ohms = Replace RABS valve

When I perform the second test, with the same settings the meter reads to the far left of the scale.

Quote:
4b Check for short between RABS ground switch & valve ground lead
1- Set the ohmmeter on 20k ohm scale.
2- Check resistance between the valve connector switch pin and valve solenoid ground pin.

Valve connector -Pin View
. . . . . . . . . . . . . . . .O
Valve switch pin ---O . . .O
. . . . . . . . . . . . . . . .O--- Valve solenoid ground pin

Resistance is greater than 10k ohms = Go to test 4c.
Resistance is less than 10k ohms = Replace RABS valve


Am I doing something incorrectly with the meter or what? Thanks.

[jermil01]

Couple of things the VSS I bought at Discount Auto was crap, I went for a drive after installing and the damn speedo was bouncing all over the place. I've reinstalled my old one and I'lll be going for adrive in a few to see if that corrects the speedo problem. As for the testingm instead of screwing around with my tired old multimeter I went out and bought a decent digital that has the autorange on it. I performed the first test again, I touch the red lead to the valve switch pin and ground the black lead on the valve body. Hopefully that's right.

Quote:
4a -Check for closed RABS valve switch
1-Disconnect RABS valve harness connector from valve connector.
2- Place ohmmeter on th 20k ohms scale.
3-Check resistance between valve connector switch pin & valve body.

Valve connector -Pin View
. . . . . . . . . . . . . . . .O
Valve switch pin ---O . . .O
. . . . . . . . . . . . . . . .O

Resistance is greater than 10k ohms = Go to test 4b.
Resistance is less than 10k ohms = Replace RABS valve

This is the reading I got.



Which if I'm reading correctly is around 1900, so that is less than 10K I'm thinking the valve body needs to be replaced. I can't seem to find it on the napa site, anyone know where I can buy one.

[jermil01]

Went through the rest of the trouble shooting and testing from the Service CD and finally go to the last one:

C7 BRAKE LIGHT WIRING
l Check for shorts in brake light wiring.
-- Disconnect module harness connector from module.
-- Turn ignition key to the on position.

REAR ABS light goes off and BRAKE light stays on
CHECK for short to ground in the 977 circuit. REFER to «wiring diagram» in this section.

Both REAR ABS and BRAKE warning lamps go off
REPLACE module.

After disconnecting the module both lights went out so I guess that is the problem.

[jermil01]

Let me ask a quick question. Is there any down side to me just unplugging the module and running without the RABS. I mean this rig is primarily an off road and weekend vehicle so I'm thinking I could get away with it. Will there be any adverse effect on my braking other than not having ABS?

[Need4racin]

Good info in this thread. Subscribed.

[El Kabong]

Originally Posted by jermil01

Let me ask a quick question. Is there any down side to me just unplugging the module and running without the RABS. I mean this rig is primarily an off road and weekend vehicle so I'm thinking I could get away with it. Will there be any adverse effect on my braking other than not having ABS?

That's what I ended up doing. My rears were dragging badly when it acted up. I didn't want to lay out the cash for a system that surprised me at times that I wanted to be in control. (I drove long enough before abs that it throws me every time it kicks in, & my reactions are backwards with it). I unplugged the module, the light went off, the brakes quit dragging, & now they act like I expect them to. I don't know if they all work like non-abs systems if unplugged, or if my rabs valve is stuck in a way that it just works out.

Btw, I believe that abs systems are good & help stopping, but my experience & reactions are based on squirreling around with non-abs systems. It makes me think that I'm on some sort ground that is allowing the tires to slip on & off. My foot leaves the pedal to try to regain traction when they kick in. Afterwards I realize what happened. I know to in my head to keep my foot on the pedal, but my split second reaction is just wrong.

[jermil01]

I guess my question is what does the valve body do when the module is disconnected? If there is no harm, rather than drop $100 bucks on a part that I really don't need, I'm just going to disconnect it. Thanks for all of the input.

[El Kabong]

On mine it acts as if it's not there with the module disconnected. The brakes seem like non-abs brakes.

[jermil01]

Originally Posted by El Kabong

On mine it acts as if it's not there with the module disconnected. The brakes seem like non-abs brakes.

Then there's my answer..I'm going to be disconnecting it this weekend.

[jermil01]

Pulled the module out this morning with no ill effect, the rig brakes fine and no more annoying light..my emergency brake light works too, so that's a plus.

[BroncoBill76]

Hi all, i just got a 1996 Bronco and know im suppose to have 4 wheel abs but didnt think that abs existed on drum brakes so i did a search and ran into this. Now i assume its clear that abs is possible on drum brakes.
My question is, does your Bronco have a abs light for the rear and another abs light for the front? I think my 96" has only 1 abs light. thanks

[jermil01]

My rig has a RABS light only.