Above is a diagram showing Ford Explorer O2 Sensor locations. If your engine is throwing a code like PO153 &#34;Upstream heated O2 sensor circuit slow response Bank 2&#34; you&#39;ll need to find your oxygen sensor locations to replace the bad unit. The diagram also shows which side of the engine holds Bank 2 and Bank 1. Bank 1 is the side of the engine with Cylinder 1. It displays the Ford V8 numbering system for O2 sensors.