The Anti-lock Braking System (ABS) is a critical safety feature in modern vehicles, designed to prevent wheel lock-up during hard braking, allowing drivers to maintain steering control. A less commonly discussed, yet crucial component within the ABS is the ABS relay. When this relay malfunctions, it can lead to issues that compromise the ABS functionality. This article delves into a specific problem: a sticking ABS relay, its symptoms, diagnosis, and solution, particularly relevant for Subaru vehicles but applicable to many cars with ABS systems.
Symptoms of a Sticking ABS Relay
A sticking ABS relay can manifest in several ways, alerting drivers to a potential problem within their car’s ABS. The most prominent symptoms include:
- Continuous ABS Hydraulic Unit Motor Operation: Even after the ignition is turned off and the car is parked, you might hear a buzzing or running sound emanating from the ABS hydraulic unit. This indicates the motor is still receiving power due to a stuck relay.
- ABS Warning Light Illumination: The dashboard ABS warning light may illuminate, signaling a fault in the system. This is often accompanied by a stored trouble code in the car’s computer system.
- Trouble Code 52: Specifically, a diagnostic scan might reveal a “Code 52”. This code often points to a fault within the hydraulic motor circuit, which can be caused by a malfunctioning or sticking ABS motor relay.
- Intermittent Issues: The problem may not be constant. Symptoms might appear sporadically, making diagnosis challenging if the condition isn’t present during inspection.
Diagnosing a Sticking ABS Relay
If you experience these symptoms, a systematic approach is needed to diagnose the issue:
- Initial Check: First, confirm if the ABS hydraulic unit motor is indeed running continuously. Listen closely, especially after turning off the ignition.
- Key-Off Test: If the motor is running, check if it continues to run even with the ignition key in the “off” position. This is a key indicator of a relay sticking closed.
- Diagnostic Code Scan: Use an OBD-II scanner to check for stored trouble codes. A “Code 52” strengthens the suspicion of a relay or hydraulic motor issue. Refer to your car’s service manual for specific diagnostic charts related to this code.
- Relay Inspection and Replacement: The most direct solution, particularly for known issues in certain vehicle models, is to replace the ABS hydraulic unit motor relay. Manufacturers sometimes release updated or modified relays to address known sticking problems. In the case of Subaru, a modified relay with part number 26735AA012 was introduced. This updated relay can often be identified by a white line under the word “Japan” on its casing. Always verify the latest part number supersession for any updates.
- Wiring Harness Check: In less frequent cases, the issue might stem from the wiring harness itself. Inspect the wiring for any damage, corrosion, or shorts. Repair or replace the wiring as necessary.
Resolving ABS Relay Sticking
The primary solution for a sticking ABS relay, especially if confirmed by symptoms and diagnostic codes, is replacement. Using the updated part is crucial, particularly if there’s a known manufacturer’s modification.
For Subaru vehicles experiencing these symptoms, replacing the ABS Hydraulic Unit Motor Relay with the modified part (26735AA012 or its supersession) is the recommended fix. Production changes incorporating the new relay were implemented starting from specific VINs for various Subaru models (Legacy, Impreza, SVX). Consulting official service bulletins or a Subaru dealership can provide precise VIN ranges for affected vehicles.
Conclusion
A sticking ABS relay, while seemingly a minor component, can lead to significant ABS malfunctions. Recognizing the symptoms – continuous motor operation and ABS warning lights – is the first step towards diagnosis. Replacing the relay, especially with an updated part if available, is often the straightforward solution. Regular car maintenance and prompt attention to warning signs ensure the continued effectiveness of your car’s vital safety systems like the ABS. Addressing issues like a sticking ABS relay contributes to overall vehicle safety and driver confidence.
