Technical 18 www.aftermarketonline.net SEPTEMBER 2025 Don’t take fault alerts at face value Tracking down a Corsa ABS fault? Sam Peters, site manager at multi-award winning Oldfields Garage in Herefordshire, says check the wiring loom first Increasing numbers of Vauxhall Corsas (2019-2023) are presenting with ABS and ESP warning lights, often accompanied by fault codes pointing to wheel speed sensors and the electronic parking brake (EPB). At face value, these symptoms naturally steer technicians toward the ABS sensors or even wheel bearing issues — a logical assumption given the dashboard alerts and stored fault data. However, both a recent technical bulletin and our repeated workshop experience point to a far simpler and more frequent root cause. Common fault codes identified were: O C003A 01: right rear wheel speed sensor circuit malfunction; O C0037 01: left rear wheel speed sensor circuit malfunction; O C1560 13 / C1561 13: electric parking brake (FSE) actuator open circuits. Additional fault codes often stored include C003A 11, C003A 12, C003A 29, C003A 2F, C003A 62, C0037 11, C0037 12, C0037 29, C0037 2F, C0037 62 and C050D 64. After checking stored diagnostic trouble codes (DTCs), reviewing live data, and consulting manufacturer technical platforms, we formulated a reliable test plan. Drawing on repeated experience with this issue, we now prioritise inspecting the wiring loom between the multi-block connector and the ABS sensor before disturbing the often-costly ABS unit. Time and again, we’ve identified wire damage near the rear wheels, particularly where the loom passes through flex points by the rear trailing arms. These areas are prone to fatigue, moisture ingress, vibration damage, and mechanical stress over time. Each rear wheel features its own dedicated sub-loom, which connects to the main loom running along the trailing arm(s). If a fault is found, the affected subloom can be replaced independently and relatively inexpensively, often preventing the need for more costly ABS sensor or wheel bearing replacements. This issue has been observed in both fully electric and internal combustion engine versions of the Corsa, suggesting a design-related vulnerability, irrespective of drivetrain. Repair strategy When investigating ABS or EPB-related faults on this model, especially when rear sensor DTCs are stored, start your diagnosis at the rear wiring looms. A single broken wire can mimic sensor failure and potentially save hours of diagnostic time if caught early. Vehicles get more complex with every new model, but sometimes it’s the simplest of fault, like wiring loom failure, that cause the biggest headaches. With a solid diagnostic process and an understanding of common weak spots, you can get to the root of the problem quickly, saving time, money, and giving customers real confidence in the fix. Simplest of faults can cause the biggest headaches Sam Peters
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