code 176 retrieved......HEGO (HO2S) SENSOR FAULT/RICH
 

Retrieved this code now for my 94 ranger. the 543 fuel pump secondary circuit fault came up also as it did the other day.

i erased the codes and will see if they come back. if they do, i will find the problem and fix it then.

which o2 sensor do you think this would mean?

These are from two independent sources:

176 = HEGO sensor circuit indicates system lean (left side)
176 = Oxygen sensor not switching - system is or was lean - Left HO2S - Fuel control