Toyota Prius 2010 Repair Manual page 441

(b) Make sure that the horn sounds.
HINT:
If the horn does not sound, inspect the horn system
9. PERFORM DIAGNOSTIC SYSTEM CHECK
(a) Perform a diagnostic system check
10. INSPECT SRS WARNING LIGHT
(a) Inspect the SRS warning light
2010 Toyota Prius
HINT:
If any of the defects is found, replace the steering pad with a new one.
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Repair Manual