hi all, just got my rebuilt tbi 2.2 up and runnin and a day or to later it put som codes out like:21(problem with oxygen sensor signal circuit. Sensor voltage to computer not fluctuating). does this mean its time for a new o2 sensor or is ther something i can do to fix this? also 13(indacates a problem with MAP sensor pneumatic (vacuum) system) this one went away after i put on some smaller vac line. And finaly 22(coolant sensor voltage to high or to low, test coolant temp sensor) that also went away after a bit but 21 still stands, and i have the usual ones like 12,31,32,33 for things ive deleted in the past dut the one that worrys me is 21 (the o2 sensor) so should i replace it?