ESP was option on ST170, been ages since I've worked on one so can't think where the button is, or indeed if it has one. If it has one I guess it will be in centre console somewhere.
Cars with ESP usually have 6 valves on the ABS hydraulic unit, rather than 4 for ABS - Doubt you can see the ABS pump easily enough to count them.

Unless there is a TC switch,can't disable TC and not ABS,easily.