Regal ABS serial data circuit diagram and table

Introduction to the Regal ABS System

The Regal anti-lock braking system (ABS) is an advanced safety feature found on many modern vehicles. It helps prevent the wheels from locking up during sudden or hard braking, allowing the driver to maintain steering control and reducing stopping distance on slippery surfaces.

At the heart of the Regal ABS is an electronic control module that constantly monitors wheel speed sensors and rapidly pulses the brakes when it detects a lockup condition. This monitoring and control process relies on the serial data communication between the wheel speed sensors, control module, and other ABS components.

In this article, we’ll take an in-depth look at the serial data circuit diagram for the Regal ABS system. We’ll examine each component, trace the flow of data signals, and provide detailed tables breaking down the wiring, PCBassembly.com/pcb-connectors/”>connectors, and Communication Protocols used. Whether you’re a professional mechanic, tech-savvy DIYer, or simply curious about how ABS works, this guide will give you a thorough understanding of the Regal ABS serial data subsystem.

Regal ABS Components Overview

Before diving into the details of the serial data circuits, let’s review the key components that make up the Regal ABS:

Wheel Speed Sensors

These sensors, typically mounted at each wheel hub, generate electrical pulses as the wheel rotates. The frequency of the pulses corresponds directly to the rotational speed of the wheel. Most Regal ABS systems use active wheel speed sensors containing a Hall effect element powered by the ABS module.

ABS Control Module

The electronic brain of the system, the control module, constantly monitors the signals from the wheel speed sensors. It looks for sudden decelerations at any wheel, indicating a lockup condition. When a potential lockup is detected, the module rapidly pulses the brake pressure at that wheel, allowing it to keep rotating. The module uses high-speed serial data communication with the sensors and valves to make these adjustments many times per second.

Hydraulic Valve Assembly

This unit contains a set of solenoid valves under the control of the ABS module. During ABS operation, the module pulses these valves to rapidly increase or decrease the brake fluid pressure to the affected wheels. Older Regal models use a motor-driven pump and accumulator to control the fluid pressure, while newer designs use a simpler and faster direct solenoid valve setup.

Miscellaneous Inputs

Depending on the exact model and options, the Regal ABS module may have additional inputs such as the brake light switch, vehicle speed sensor, steering angle sensor, accelerometers, etc. These provide additional data the module can use to fine-tune the ABS operation and integrate with stability control and traction control systems if equipped.

Regal ABS Serial Data Circuit Diagram

Now let’s examine the actual circuits and wiring connecting the Regal ABS components. We’ll use industry-standard symbols and terminology to diagram the flow of data between each part.

Wheel Speed Sensor Circuits

Each wheel speed sensor connects to the ABS control module via a twisted pair of wires. One wire provides DC power (usually 12V) from the module to the sensor, while the other wire carries the pulsed speed signal from the sensor back to the module. The sensors are wired in parallel so that a fault in one sensor doesn’t disable the others.

Here is a simplified schematic showing the typical circuit for the Regal front wheel speed sensors:

        Front Left    +---------+    Front Right
        Wheel Sensor  | ABS     |   Wheel Sensor 
        -----+------> | Control |<-------+------
+12V ------| |        | Module  |        | |------ +12V  
            |         |         |         | 
Signal <----|-------> |         | <-------|------ Signal
        -----+------> |         |<-------+------
                      +---------+

And the rear wheel sensors:

        Rear Left     +---------+    Rear Right
        Wheel Sensor  | ABS     |   Wheel Sensor
        -----+------> | Control |<-------+------  
+12V ------| |        | Module  |        | |------ +12V
            |         |         |         |
Signal <----|-------> |         | <-------|------ Signal  
        -----+------> |         |<-------+------
                      +---------+

Hydraulic Valve Circuits

The hydraulic valve assembly contains several solenoid valves that control the flow of brake fluid during ABS operation. These are typically normally-open valves that close when energized.

Each valve solenoid has two wires — one power and one ground. The ABS module switches the ground side to energize the solenoids as needed, with the power side connected to a relay or fuse for protection.

Here is an example valve circuit diagram:

                +---------+
 +12V --->o-----|Power    |    
               |         |-------XXXXX-----> Valve 1 Solenoid
               |  ABS    |      Coil
               | Control |    
               | Module  |-------XXXXX-----> Valve 2 Solenoid              
               |         |      Coil
           |---|Ground   |  
           |   +---------+
          GND

Other Inputs

Depending on the model, the Regal ABS may integrate other input signals such as:

• Brake light switch to detect brake pedal application
• Vehicle speed sensor, often shared with speedometer and transmission controller
• Steering angle sensor for stability control
• Accelerometers for hill-start assist and stability control

These typically connect to the ABS module via discrete wires or through a vehicle Data Bus like CAN. The exact wiring details vary significantly by make, model, and installed options.

Regal ABS Serial Data Communication Protocol

The Regal ABS components communicate using a proprietary serial data protocol. Unlike the CAN bus used for general vehicle data, this is a dedicated link carrying only ABS data.

Digital data is transmitted in frames, with each frame containing a start bit, 8 data bits, and a stop bit. The frames are transmitted asynchronously at a fixed baud rate, which can vary between model years but is typically in the 33.3 kbit/s to 41.7 kbit/s range.

Here is the structure of a typical ABS data frame:

The bits are encoded using a non-return-to-zero (NRZ) format where a 1 is represented by a high voltage and a 0 by a low voltage:

Bit value:   1  0  1  1  0  1  0  0
           ___    ___  ___     ___ 
Voltage:      |__|   |_|  |__|    |___

The wheel speed sensor data uses a pulse-width encoding, where the time between rising edges indicates the wheel speed. A longer interval means a slower speed. The ABS module measures these intervals with microsecond precision to calculate the speed of each wheel.

For the solenoid valves, the ABS module sends a command frame indicating which valves should be energized. Each bit in the data byte corresponds to a particular valve, with a 1 indicating on and 0 off.

Regal ABS Diagnostic Trouble Codes

When the ABS module detects a fault with the sensors, valves, or wiring, it logs a diagnostic trouble code (DTC) in its memory. It also lights the ABS warning light on the instrument cluster to alert the driver.

To retrieve these codes, a technician can use an OBD-II scanner or a dedicated ABS scan tool connected to the vehicle’s diagnostic port. Each DTC consists of a letter and 4 digits identifying the specific fault.

Here are some of the common DTCs for the Regal ABS system:

A full list of Regal ABS DTCs can be found in the factory service manual for each specific model year. The manual will also have step-by-step diagnostic procedures to help pinpoint the root cause of each trouble code.

Frequently Asked Questions (FAQ)

What are the symptoms of a faulty wheel speed sensor?

Common symptoms of a bad wheel speed sensor include:
– The ABS warning light staying on
– Pulsating brake pedal when braking hard
– Increased stopping distance
– Traction control or stability control not working
– Speedo meter reading incorrectly

If you suspect an issue with a wheel speed sensor, have the ABS system scanned for trouble codes to verify the problem.

Can I drive with the ABS light on?

Your base brakes will still work with the ABS light on, but you won’t have anti-lock functionality. This means your wheels may lock up and skid during hard braking, especially on slippery roads.

It’s okay to drive short distances with the light on, but you should diagnose and repair the issue as soon as possible for safety reasons. A lit ABS light will also disable any traction control or stability control systems.

How much does it cost to fix an ABS problem?

The cost to repair an ABS issue depends on the root cause. A simple wheel speed sensor replacement may only be a couple hundred dollars. But if the hydraulic unit or ABS module needs replacing, the bill can easily exceed $1000.

A proper diagnosis with an ABS scan tool is always the first step. This will retrieve any stored trouble codes pointing to the specific problem area. From there, a knowledgeable mechanic can give you an accurate repair estimate.

Can I replace just one wheel speed sensor?

On some older vehicles, you can replace individual ABS speed sensors. But on most modern cars, it’s recommended to replace them in pairs (both fronts or both rears).

This is because a new sensor may have slightly different output characteristics than the old sensor on the opposite side. This difference can cause the ABS module to think one wheel is turning slower than the other, leading to erratic ABS behavior. Using a matched pair of new sensors eliminates this potential issue.

What is the difference between ABS and traction control?

ABS and traction control are closely related but use the brakes in different ways:

• ABS rapidly pulses the brakes at individual wheels to prevent lockup and skidding under hard braking. It helps you stop in a shorter distance and maintain steering control.

• Traction control uses the ABS valves to briefly brake spinning drive wheels when accelerating. This transfers more engine power to the wheels with better traction, helping you accelerate on slippery surfaces.

So while ABS works while braking, traction control comes into play when accelerating from a stop or powering through a corner. On Regals and many other vehicles, the ABS module also serves as the traction control module using additional sensors and software.

Conclusion

The Regal ABS serial data communication system is a critical part of the overall anti-lock braking system. By understanding the Circuit Diagrams, wiring details, and communication protocols used, technicians and DIYers can more effectively diagnose and repair ABS issues.

The information in this article should serve as a solid foundation for anyone working on a Regal ABS system. But always consult the factory service manual and wiring diagrams for your specific year and model before starting any repairs.

With proper care and feeding, the Regal ABS will provide many years of safer stopping under all road conditions. So take the time to understand its inner workings, and don’t ignore that little ABS warning light if it comes on. Your brakes will thank you!