Bad ABS Module Symptoms: How to Diagnose and Fix It

Troubleshooting a Bad ABS Module: Common Signs and Fixes

The ABS module is the control center of this system. As you’ll see below, the module consists of a circuit board and solenoid driver coils. When energized, the solenoid coils open the valves in the ABS valve body, allowing them to flow pressurized brake fluid to the wheels. The module ensures that the brakes are applied evenly and at the right pressure. When the module malfunctions, it can compromise vehicle safety, leading to potential issues during braking. In this article, we’ll explore the symptoms of a bad ABS module, how to diagnose the problem, and what steps to take to fix it.

This image shows an ABS module consisting of the control module, valve body, and pump.

Symptoms of a Bad ABS Module

A failing module can exhibit several warning signs that shouldn’t be ignored. If you notice any of these symptoms, it’s essential to get your vehicle checked immediately:

1) ABS Warning Light: The most common sign of a problem is the illumination of the ABS warning light on your dashboard. This light usually appears as a yellow or red indicator with the letters “ABS.” When this light comes on, the ABS module has detected a fault within the system. However, a lit ABS light alone isn’t always conclusive; it could also indicate issues with the wheel speed sensors, wiring, or other ABS components.

2) No Speedometer: Because the module must know the vehicle speed, the vehicle speed data usually runs through the ol module first, before going to the speedometer. When it fails, it’s not uncommon to lose your speedometer reading.

3) No ABS function: Any time the ABS warning light is on, your ABS function is disabled. You can still brake the vehicle, but you won’t have any ABS braking.

4) Increased Stopping Distance: One of the primary functions of ABS is to maintain traction and reduce the braking distance during hard stops. If you experience longer stopping distances or notice that your car skids easily, it might be due to a failed module that isn’t correctly regulating brake pressure.

5) Loss of Traction Control or Stability Control Features: Many modern vehicles integrate the ABS with traction control and stability control systems. A failed module can lead to problems with these systems, triggering warning lights for traction or stability control and causing a loss of function in these features.

The most common failure issues

1) Power regulator failure: The circuit board relies on power from a transformer, power transistor, capacitors, and relays. If any one of those fails, it will set a trouble code and a dash warning light.

This image shows a damaged power transistor on an ABS module circuit board.

2) Shorted solenoid coil driver: The solenoid coil is powered on and off by a transistorized driver relay. A short in the solenoid windings or a failure in the driver will cause the ABS module to set a trouble code and dash warning light.

The ABS solenoid coils are soldered onto the circuit board and can be replaced if they develop an open or a short condition.

Diagnosing a Bad ABS Module

• Check the fault codes: Use an OBD-II Scanner to read the trouble codes. The codes will provide specific information on whether the problem lies within the module, the wheel speed sensors, or other related components.

Inspect for Physical Damage: Check the module and its connections for visible damage, rust, or water intrusion, which could affect its performance.

How to Fix a Bad ABS Module

If you’ve diagnosed the module as the source of the problem, you have several options for repairing or replacing it:

1) Rebuilding or Replacement: In most cases, the unit must be repaired by a professional rebuilder or replaced with a new or used unit. The module is connected to the ABS valve body and can be removed easily using a regular or security TORX bit.

• The least expensive way is to remove it and send it off to a module rebuilder like modulemasters.com. That way, your module can be repaired without having to deal with reprogramming. Rebuilding prices vary, but are often in the $200 range.

• The 2nd least expensive way is to find a used module. However, once installed in your vehicle, it must be reprogrammed to match your vehicle’s VIN. The ABS module programming must communicate properly with the ECM and Body control module, and it must know the exact year, make, model, and factory features for your vehicle, as well as the factory vehicle weight. Any repair shop that has programming capabilities can reprogram an ABS module as long as you locate the exact replacement part number for your vehicle.

• The most expensive way to fix the problem is to buy a brand new ABS module and then have it programmed to your vehicle. New ABS module prices range from as little as $500 to as much as $2,200 depending on the vehicle.

Reinstalling the new, used, or rebuilt ABS module

Simply reinstall the new, used, or repaired module back in place on the valve body, making sure to use a new gasket or non-corrosive sealant. Tighten the screws to factory specifications and reconnect the electrical connectors.

©, 2024 Rick Muscoplat