Steve Magoffin made another important breakthrough at the end of a session as Sussex continued to keep the pressure on Yorkshire.
Magoffin had Adam Lyth caught on the fine leg boundary as Yorkshire reached the tea interval on 131-2.
Lyth had played watchfully for his 66 – from 153 balls – but was tempted into a hook which he top edged to Jon Lewis.
The Yorkshire opener had dug in well with Jack Leaning – who put on 73 together – in the face of some disciplined bowling from Magoffin.
The Aussie seamer has now bowled 16 overs in the match for figures of 2-11 with ten maidens. Together with James Tredwell they tied down Lyth and Leaning after lunch with only eight runs coming in the first half hour.
Leaning remains unbeaten on 39 – from 96 balls – while skipper Andrew Gale is yet to score.