what does the codes 1188 and 1189 mean about the car ? on 2000 BMW 328i

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Asked by for the 2000 BMW 328i
P1188 - Oxygen Sensor Heater High Resistance Upstream
P1189 - Oxygen Sensor Heater Type 1 Low Resistance Upstream
test procedures for these codes. Autozone have some popular workshop manuals for free on line once you register (for free) on their website .There is a company that independent auto repair shops "buy" their information from that offer a very reasonable service to do it yourselvers. You get a one year subscription to year make and model specific repair procedures, service bulletins, component locations, wiring diagrams ect.... great quality information same as the professionals have ,much better than generic workshop manuals from parts stores, much cheaper than the factory manual. or try and get an online repair manual subscription.
do you feel I should replace the oxygen sensors