Possible causes Crossed HO2S harness connectors (downstream)Crossed HO2S wiring at the harness connectors (downstream)Crossed HO2S wiring at the 104-pin harness connectors (downstream) Symptoms – Engine Light ON (or Service Engine Soon Warning Light) P1129 FORD OBD Code Description The heated oxygen sensor (HO2S) monitor determines if the HO2S signal response for a fuel shift corresponds…