ABS Faults: Reading Blink Codes and Finding Wheel Speed Sensors
An ABS light means your brakes won't modulate in a skid. We cover reading codes and the wheel speed sensor failures behind most faults.
What the ABS light means
An illuminated ABS lamp means the antilock system is disabled — the brakes still work, but they can't modulate to prevent wheel lockup in a hard stop. It's a DOT violation and a real safety risk, especially on steer and trailer axles. The system stores a blink code (or a readable code) that tells you which wheel or component is at fault.
Reading blink codes
Truck and trailer ABS both report codes by flashing the warning lamp a set number of times. We read the blink sequence, which maps to a specific wheel or modulator fault. Most ABS faults are wheel speed sensor issues — the sensor magnetized with debris, out of air gap, or the tone ring damaged — not the modulator itself.
The MTG approach
We read the code, inspect and clean the named wheel's speed sensor and tone ring, reset the air gap, and re-check the signal in live data. If the sensor tests good, we check the harness and the modulator valve. We carry trailer and tractor ABS readers and common sensors on our mobile units, so most ABS faults clear roadside.
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