It's the power steering pressure sensor. When you're sitting idle and turn the steering wheel it senses the load and sends a signal to the ECU to compensate and prevent the engine stalling.
Funny how yours has three wires, mine has only got 2. Anyway if you can sit with the engine idling and your foot off the accelerator, turn the steering wheel a bit to each side. The engine idle should increase very slightly, as long as it doesn't decrease you should be fine.
'93 16V Mondeo saloon
Full factory RS setup lowered on 17s
K+N 57i, splitfire leads, chipped, full aluminised twin-exit exhaust
Sounds by Alpine, Infinity, Vibe, JBL
First Mondeo with indiglo gauges
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