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121 is the air mass meter, 221 is fuel trim to lean at part load and 321 is no knock enrichment signak from the igntion computer. I would suggest replacing the air mass meter that is mounted to the air cleaner housing for the first 2 codes. the 3rd code I have seen this set by low voltage to computer at start up due to bad fuel pump relay. replace both of them. the relay is chaep.
If I heped please Hit the ACCEPT button. feel free to ask more questions. Thanks Mike
ok 121 is map sensor signal faulty or missing. it is located on the left strut tower near the firewall, in a silver box. check to make sure the vacuum line is not plugged. the 221 is o2 sensor signal missing or faulty, the 321 is signal shorted to ground or missing. 02 sensors do go bad, have seen several of the map sensor vacuum lines plugged or have water at the low spot reducing signal to map sensor. I would suggest replacing o2 sensor, and if map sensor is pluged in and vacuum line is clear to replace it. check to make sure the cold start is plugged in, it is under the intake manifold on the side towards the engine.
If I helped please hit the ACCEPT button. thnaks Mike
If I helped please press the ACCEPT button. if you need to ask more questions feel free. Thanks Mike