、。
If the car happens to have trouble, I'll go by bus.
Literal
By-chance car's condition [subject-が] bad-was-[conditional-たら], I [topic-は] bus [with-で] go.
調子 ('condition, state of function') is used commonly with vehicles, machines, and health. 調子が悪い ('condition is bad') means 'is malfunctioning' or 'feels unwell' depending on context. The past-tense 悪かったら is the conditional form of an i-adjective — drop the い, add かったら.