You’re enjoying a drive when the ABS light on your dashboard suddenly starts glowing. You also start to feel your anti lock brake stiffen, and your brake pedal becomes unresponsive.
Looks like something’s wrong…and that ABS light has something to do with it.
But what are ABS brakes in the first place?
And more importantly, what happens when you experience ABS module failure?
This Article Contains:
- Understanding the Anti-Lock Braking System (ABS)
- What Happens if the ABS System Fails?
- A Closer Look At The ABS Module
- Signs of a Faulty ABS Module
- The Cost of ABS Control Module Replacement
Let’s get started.
Understanding the Anti-Lock Braking System (ABS)
To understand the ABS control module, we first need to know what an ABS is.
The Anti Lock Braking System (ABS) is designed to prevent your wheels from locking, skidding, or hydroplaning during heavy braking. It’s an additional safety feature found on many modern vehicle designs that allow for a faster, controlled stop and has been available since the 1980s.
Stability controls help prevent your car from skidding even when the brakes aren’t applied. Here, the anti lock brake components work with your traction control system to slow down the wheel speed or your engine’s power when necessary.
So, what makes up an anti-lock brake system?
The most common configuration consists of these components:
1. ABS Sensor
The ABS wheel speed sensor detects the speed of a rotating wheel and feeds that information to the ABS control module.
2. ABS Module
The ABS control module is a microprocessor that runs diagnostic checks on a vehicle’s anti-lock braking system and controls the ABS modulator. It uses data from the speed sensor to manage the valve system in the ABS modulator to restore hydraulic pressure.
3. ABS Pump
The ABS pump is also called the ABS modulator, Hydraulic Control Unit (HCU), or even ABS motor. It typically comprises an electrical engine, ABS valves operated by solenoids, and a base where brake hoses (from the master cylinder to brake calipers at each wheel) are connected.
The hydraulic unit allows electric signals from the ABS control module to control the hydraulic pressure in each brake line. It does this through the solenoid, a magnetic coil that opens and closes a valve that regulates brake fluid flow. The number of solenoids and valves used can vary depending on the ABS modulator design.
Now that we’ve gone over the ABS system, let’s get into the ABS module.
A Closer Look at the ABS Module
The ABS control module acts as the “brain” of the entire anti-lock brake system. It processes information from the ABS sensors and controls the brake pressure through the ABS modulator.
ABS modules are also called:
- ABS control unit
- ABS controller
- ABS unit
- Electronic Control Unit (ECU)
The control module is installed and mounted in the engine compartment in most common car designs. Sometimes, it’s located in the frame rail on the left side of the vehicle.
If an ABS sensor detects that the vehicle is skidding or losing traction, it sends a signal to the ABS module to rapidly pump the brake. This produces intermittent braking and some amount of steering control.
Here’s a snapshot of events between the ABS sensor and ABS control module to give you an idea of how this rapid pumping works:
- The wheel sensor detects one tire spinning substantially slower than the others while braking and transmits this information to the ABS control module.
- The control module releases the brake pressure on that wheel very briefly so the tire can regain grip.
- The control module then reapplies the brakes on that wheel.
- This process repeats several times per second whenever a tire loses grip under braking.
So, how do you know if you have a failing ABS module?
Signs of a Faulty ABS Module
Here are the obvious signs that can help you detect an ABS control module issue:
1. The ABS Warning Light Glows
This is the most common sign of problems with the ABS system. Just be aware that the dashboard ABS warning light is supposed to come on for a few seconds when you start a vehicle, so don’t panic.
If the ABS light remains glowing, try turning the ignition key off and back on, like rebooting your computer. Some transient issues may confuse the ABS control module, and restarting the car could help clear that.
If restarting doesn’t make the ABS light go away, it’s probably time to call your mechanic. The ABS light triggers a code that helps your mechanic pinpoint which ABS component is causing the problem.
If you’re driving and the ABS light suddenly glows, this can indicate a failure with one of the ABS system components, including the ABS control module.
Again, don’t panic.
Some components of the anti lock brake system may still function despite the glowing ABS light. The anti-lock may not work, and stability control and traction control might also be disabled, but as long as your conventional brakes aren’t compromised, you should still be able to brake your car just fine.
Keep in mind that select vehicle groups (older cars) equipped with earlier ABS systems might not have an ABS light. These use the Check Engine Light instead.
2. The Brakes Lock Up
The ABS system prevents any wheel from locking up during heavy braking. So, when an ABS control module fails, you’ll likely notice it when applying more braking pressure.
A bad ABS module can behave erratically, making your brakes lock up even under normal braking. You might even notice unusual behavior from the brakes, like random clicking noises. These can also indicate ABS module failure.
Here’s something to note — if one tire is consistently locked, it might not be the vehicle ABS but a stuck caliper instead.
3. An Unresponsive Brake Pedal
Your brake pedal may slowly become unresponsive over time.
At first, you’ll have to press the pedal a couple of times to get some braking action.
Eventually, you’ll have to press down multiple times to get it to work, indicating a deteriorating ABS module.
4. Increased Pedal Effort
With a fully functional braking system, the brake pedal needs minimal effort to slow the vehicle.
If you notice more pedal effort required to generate the same amount of braking pressure, there could be a problem with the ABS control module. Again, brake pedal issues like increased foot effort can mean other things, like worn brake pads or a failing brake booster, so be sure to have your mechanic check everything.
5. Speedometer Failure
There are rare cases where an ABS control module failure affects the speedometer. It’ll either show you the wrong speed, or the needle will rest at 0 mph.
Next, the brake light or Check Engine Light will likely switch on. Even if those lights don’t come on, a faulty speedometer is a reasonable cause to have your car checked out.
Essentially, if you have an inkling that your ABS control module may be going haywire, get to a mechanic quickly.
Or better — get one to come to you.
What Happens if the ABS System Fails?
If your vehicle’s ABS brakes fail, your normal brakes should still function and decrease your wheel speed— provided nothing’s wrong with them. With an ABS module issue, you just have to be more careful when braking to avoid skidding.
The Cost of ABS Control Module Replacement
By now, you’re likely wondering how much an ABS module repair would cost. The price can vary greatly depending on your vehicle’s make and model — anywhere from $325 to $2200.
Note: Since the ABS unit is made of high-quality and high-priced system components, you can recycle these select vehicle auto parts in the event of ABS failure.
Usually, when the ABS light glows, it points to wheel speed sensor issues as they are the most vulnerable ABS component.
However, suppose you’re not dealing with a simple speed sensor issue?
In that case, it might not be possible to determine what part of the ABS control module needs replacement without a complete diagnosis from your mechanic.
If you feel that your ABS module is faulty, don’t worry. It’s easy to get hold of a mechanic for an ABS control module replacement, especially with AutoNation Mobile Service conveniently available seven days a week.
You don’t even have to drive your car to a repair shop — all you have to do is contact us, and we’ll send a mechanic over to your location of choice to deal with your ABS module issue right in your driveway!
AutoNation Mobile Service provides a 12-month, 12,000-mile warranty for all repairs and ensures all maintenance and repairs are executed with high-quality equipment and replacement auto parts.
Don’t ignore any ABS issues — whether it’s a problem with the ABS control module, sensor or if the ABS light is acting strange. Contact AutoNation Mobile Service today!