All 45 exams / S-series / ASE S4 Brakes
S4
ASE S4 Brakes
School buses
What's on the S4 exam?
1
Air Brakes Diagnosis and Repair
2
Hydraulic Brakes Diagnosis and Repair
3
Antilock Brake System (ABS), Automatic Traction Control (ATC), Electronic Stability Control (ESC), and Collision Warning/Avoidance System Diagnosis and Repair
Content-area outline only, authored from ASE's public task-list structure. No test question, answer, or diagnostic scenario is reproduced from ASE or any prep publisher.
S4 quick reference S-series
Categoryrepair technician
Work experience2
Question count60
Time allowed75 minutes
Fee$62
Recert cycle5 years
Recert pathRetest (25-question, 30-minute recert version) every 5 years, or the ASE Renewal App.
Source: https://ase.com/wp-content/uploads/ASE_SchoolBus_Study_Guide.pdf.
Checked 2026-07-30.
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