Describe what you observed
Record when the issue started, when it occurs and any displayed warning. Observations help the workshop; guessing the cause first can steer discussion toward an unrelated component.
Request a breakdown
Ask about diagnostic charges, proposed work, parts and labour. Agree that additional work requires contact first. FTC guidance recommends written estimates; use that organizational principle without assuming US legal rules apply locally.
Keep comparable records
Compare equivalent items between workshops and ask why scopes differ. After completion, compare the invoice with the agreed work and save it in your vehicle record. Ask for an explanation of results you do not understand.
Sources & references
Use the owner’s manual for your exact model and year; symbols and instructions can differ.