What does bank 1 mean and system 1 on code p0170

Question

ford contour 98 2.0L
What is bank 1 and system 1?
Is this specifying up or downstram o2 sensors?

Answer 1

P0170 Fuel trim malfunction Bank 1

You only have 1 Bank. What detects the fuel trim malfunction is the upstream 02 sensor, this is the engine management sensor, Sensor 2 is the downstream 02 sensor this is the catalytic monitor sensor, Fuel trim malfunction are mostly vacuum leaks that gets pass the MAF (mass airflow sensor) inspect your PCV vacuum hose for any rips or torns or disconnected vacuum lines,