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66-96 Ford Broncos - Early & Full Size
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George Coleman

ABS

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I have a 1996 Bronco, I have narrowed the problem to two items I hope.  When braking and turning at the same time I experience pedal travel half way down and a pulsating pedal as well. Could this be the ABS control ECU or should I be looking to replace the ABS hydraulics module?  Thanks for the help, just a note I have rebuilt the front brake system completely hoses, rotors ,calipers, hubs bearings.

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Yo George,

I assume this  happens only while Turning.

from 96 Bronco Workshop Manual http://www.diesel-dave.com/vehic/manual/stj/stjs630l.htm  Read more.

  • Excessive Brake Pedal Travel, Brake Pedal Feels Spongy When Fully Applied
  • Rear brakes out of adjustment.
 
  • Front wheel bearing out of adjustment.
 
  • Brake master cylinder or power brake booster dash unit mounting loose.
  • TIGHTEN nuts and bolts to specification. REFER to Section 06-06.
 
  • Front or rear disc brake caliper attachment loose.
 
  • Worn or damaged self-adjusters.
  • REMOVE brake drum and CHECK rear brake shoe and lining for proper adjustment. REPLACE brake shoe adjusting lever. REFER to Section 06-02.
 
  • Brake pedal or support improperly mounted.
 
  • Worn or damaged brake linings.
 
  • Brake drum out-of-round or front or rear disc brake rotors with excessive runout.
 
  • Worn or damaged four wheel ABS hydraulic control unit (Bronco only).
 
  • Worn or damaged RABS valve accumulator (F-Series only).
 
  • Brake tubing improperly positioned.
  • CHECK brake tubing for misposition near heat source. Fluid can boil and result in spongy pedal response.
 
  • Low brake fluid level.
  • FILL as required.
 
  • Clogged brake master cylinder filler cap hole.
  • REPAIR or REPLACE brake master cylinder filler cap.
 
  • Air in system.

4WABS Overview; "...The 4-wheel anti-lock brake system (ABS) prevents wheel lockup by automatically modulating the brake pressure during an emergency stop. By not locking the wheels, the driver can improve steering control during hard braking and stop the vehicle in the shortest possible distance under most conditions. The ABS controls both front and rear brakes separately. The brake pedal force required to engage the ABS function may vary with the road surface conditions. A dry surface requires greater force, while a slippery surface requires much less force. During the ABS operation, the driver will sense a pulsation in the brake pedal, accompanied by a slight up and down movement in the pedal height. In addition, a mechanical noise from the engine compartment may be heard. The pedal effort and pedal feel during normal braking are similar to that of a conventional power brake system. When the brakes are applied, fluid is forced from the master cylinder outlet ports to the anti-lock hydraulic control unit (2C215) inlet ports. This pressure is transmitted through three normally open solenoid valves contained inside the anti-lock hydraulic control unit, then through the outlet ports of the anti-lock hydraulic control unit to the wheels. The primary (rear) circuit of the master cylinder feeds the rear brakes. The secondary (front) circuit of the brake master cylinder (2140) feeds the front brakes. If the anti-lock brake electronic control module senses that a wheel is about to lock, based on wheel speed sensor data, it pulses the normally open solenoid valve closed, for that circuit. This prevents any more fluid from entering that circuit. The anti-lock brake electronic control module then looks at the sensor signal from the affected wheel again. If that wheel is still decelerating, it opens the normally closed solenoid valve for that circuit. This dumps any pressure that is trapped between the normally open valve and the brake back to the reservoir. Once the affected wheel comes back up to speed, the anti-lock brake electronic control module returns the valves to their normal condition allowing fluid flow to the affected brake. The anti-lock brake electronic control module monitors the electromechanical components of the system. Malfunction of the Anti-Lock Brake System will cause the Anti-lock brake electronic control module to shut off or inhibit the system. However, normal power assisted braking remains. Malfunctions are indicated by the amber ABS warning light inside the vehicle. The 4-wheel anti-lock brake system is self monitoring. When the ignition switch is placed in the RUN position, the anti-lock brake electronic control module will perform a preliminary self check on the anti-lock electrical system indicated by a momentary illumination of the amber ABS warning light in the instrument cluster. During vehicle operation, including normal and anti-lock braking, the anti-lock brake electronic control module monitors all electrical anti-lock functions and some hydraulic operations. In most malfunctions of the anti-lock brake system, the amber ABS warning light will be illuminated. However, most malfunctions are recorded as a coded number in the anti-lock brake electronic control module memory and assist in pinpointing the component needing service. If system is OK, Code 16 will be present. The anti-lock brake electronic control module is located in the engine compartment behind the driver's side head lamp on a bracket mounted on the surface of the plastic fender apron. It is an on-board diagnostic, non-repairable unit consisting of two microprocessors and the necessary circuitry for their operation. These microprocessors are programmed identically. The anti-lock brake electronic control module monitors system operation during normal driving as well as during anti-lock braking. In addition, the anti-lock brake electronic control module provides a speed signal to the programmable speedometer/odometer module (PSOM). Under normal driving conditions, the microprocessors produce short test pulses to check the electrical system without any mechanical reaction. The anti-lock brake electronic control module continuously monitors the speed of each wheel to determine if any wheel is beginning to lock. When a wheel locking tendency is detected, the anti-lock brake electronic control module signals the appropriate solenoid valve in the anti-lock hydraulic control unit (2C215) to open or close as well as the pump motor to turn on and recycle brake fluid back to the brake master cylinder (2140). This results in moderate pulsations of the brake pedal (2455) and pump noise which may be heard in the passenger compartment. During normal braking, the brake pedal feel will be identical to a standard brake system. Most concerns which occur to the anti-lock brake system will be stored as a coded number in the Keep-Alive Memory (KAM) of the anti-lock brake electronic control module. This means that once a code is stored, it will be retained by the anti-lock brake electronic control module even with the key in the OFF position. The codes can be retrieved by following the on-board diagnostic procedures. A new light truck 4-Wheel ABS was introduced as standard equipment on the 1993 Explorer and Bronco, and it was revised in 1994 on Broncos, requiring a different control module revision for 94-96 Broncos, compared to the original 93 Bronco module. Although this system shares some of the features of passenger car 4-Wheel ABS and some of the features of light truck Rear ABS (RABS), it has its own unique features, especially when it comes to diagnosing concerns. Here are some general features of the light truck 4-Wheel ABS, some of which are common to the other systems as well: System prove-out at vehicle start-up of the light truck 4-Wheel ABS is the same as for passenger car and 4-Wheel light truck ABS. The amber anti-lock warning light will come on as soon as the vehicle is turned on or started to verify bulb operation, and will go out after 2-3 seconds, provided everything is normal. The 4-Wheel ABS operates in 4 x 4 as well as 4 x 2. In ABS mode, the brake pedal will pulsate and the pump motor noise may be heard from the engine compartment. When ABS codes are read out, code 16 will be present if the system is OK. This code is similar to the EEC's code 111. It basically means that the 4-Wheel ABS Electronic Control Unit (ECU) is indicating that everything is functioning properly electrically. In other words, the components, such as the pump motor and the valves, will activate when needed. Conventional bleed is all that is required for service on the new 4WABS including unhooking brake lines from the hydraulic controller (HCU). However, if the HCU is replaced, a special bleed box and electrical jumper will be required to bleed the replacement HCU. This procedure is not the same as for the passenger car systems....; by Ford

miesk5 Note; for all Resistance tests, battery needs to be disconnected; remove Negative cable at battery.

4WABS Self Test & Test Connector Diagram, Component Locations, DTCs, 93-96; USE THIS PROCESS! "...The 4WABS TEST Connector is red; located at the left-hand side (driver's side) of the engine compartment and marked ANTI-LOCK TEST; Light Flash Technique 1. Note: If 12V test light is not available, the amber ABS warning light also flashes during this test. Locate test connector in the engine compartment and install 12V test light between Pins C and E. 2. With the ignition off, jumper Pin E to B. 3. Turn key to RUN position. 4. Remove jumper between Pins E and B after 5 seconds. 5. Count light flashes of test light or amber ABS warning light..." read more; miesk5 Note; for all Resistance tests, battery needs to be disconnected; remove Negative cable at battery

4WABS Pin-Point Testing in 93-96 Bronco; This is same as in Ford EVTM/PCED/Workshop Manual 
Source: by Ford via Chilton & miesk5

All vehicles use a brake warning light in the instrument cluster to warn of system malfunctions. The red warning light for the brakes can show three things -- that either the parking brake is not fully released, that the brake fluid level is low in the master cylinder reservoir or the vacuum pressure is low on diesel engine vehicles.

George, I've had nausea all day, so I have to lay down again.  See more 4WABS INFO in my site

Some urls have two parts, so delete the first part. 

 

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I think I have replaced all I can at this point, I will replace the dash light and take it to the Ford dealer and let them have at it. It needs someone that has a ABS code reader I guess. Thanks for the help hop you feel better.

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Yo Georg,

No abs code reader needed.  DIY.

4WABS Self Test & Test Connector Diagram, Component Locations, DTCs, 93-96; USE THIS PROCESS! "...The 4WABS TEST Connector is red; located at the left-hand side (driver's side) of the engine compartment and marked ANTI-LOCK TEST; Light Flash Technique 1. Note: If 12V test light is not available, the amber ABS warning light also flashes during this test. Locate test connector in the engine compartment and install 12V test light between Pins C and E. 2. With the ignition off, jumper Pin E to B. 3. Turn key to RUN position. 4. Remove jumper between Pins E and B after 5 seconds. 5. Count light flashes of test light or amber ABS warning light..." read more; miesk5 Note; for all Resistance tests, battery needs to be disconnected; remove Negative cable at battery

4wabscomponents.jpg

See codes at http://www.supermotors.net/registry/media/255501_1

 

I have the Ford detailed code troubleshooting at 4WABS Pin-Point Testing in 93-96 Bronco; This is same as in Ford EVTM/PCED/Workshop Manual 
Source: by Ford via Chilton & miesk5

 

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Well I did the abs light test got 7 short and 1 long ,, code said its the RABS valve HCV is bad! So do I take a chance and find someone to replace it or just bypass the ABS system all together and take out the ABS warning light?  The reason I ask this if I have to take out the dash bezel unit it will be its last as all of the plastic pieces have broke off I have glued them for the last time. Thanks for the help George Coleman

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Yo George,

See to say, there isn't a 71 Code.

I pulled the bulb after the control module puked and yard modules turned out bad as well, with no returns. 

Screenshot_20180908-160506.jpg

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I ran this 8 times the wife read the dash light and I used a test light, wait 5 seconds after the key was placed into the run mode. pulled the jumper got 1 long 7 short then 1 long on my end. So what next try it again?? Or just bypass it??

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Yo George,

Can you try this Procedure?
1) Ignition OFF.
2) Jumper pin E to pin B. Even a paper clip will do.
3) Ignition to RUN (not start).
4) Remove jumper after 5 or more seconds have elapsed.
6) Go in and read the codes flashed out by the ABS light.
All codes are 2 digits long. 3 to 6 seconds between digits in the same code. 15 seconds between codes.

I am guessing you have code 17, so check the cab fuses 2, 8 & 5.

If same, bypass the 4WABS control module.

4WABS Control Module CONNECTOR Bypass for PSOM Operation due to Bad 4WABS Control Module; "...jumper 14 to 21, & 39 to 22..." MIESK5 NOTE;. I did this on our 96; The 4WABS control module was toast due to 2 microprocessor failures...
ABSConnectorw-jumpers.jpg?w=480&h=480&fi

Pic by Turboghost

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Yo George,

YW!  No need to remove bulb with bypass.

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So if I bypass I will take the two wires out from the wiring harness  make the connection and I can still plug the harness back into the ABSECU right? This will make the light go out each time I start the Bronco. I will need to make the two leads I pulled out water proof correct?   Checked the fuses all were ok.

Edited by George Coleman
add on

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If I do the bypass of the ABS ECU by wiring the two that I need to jumper out side of the harness can I then plug the ABS back into the old computer ECU unit. Or do I need to leave the whole unit unplugged . Thanks George Coleman

Edited by George Coleman

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Just a not I did the bypass and I still had to remove the ABS light in the dash and for some reason I got a Check Engine light so I had the clear to clear it the code reader said no codes?? Any way thank again for the help. 

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