Closed Loop Control Function Bank 1

Check these first

• An oxygen sensor 1 bank 1 that reads rich and will not switch
• A mass air flow sensor that reads out of range
• A vacuum leak or fuel pressure fault leaning or richening bank 1
• A poor connection at the oxygen sensor 1 bank 1 connector

What to do next

1. Read oxygen sensor 1 bank 1 voltage and fuel trim on a scan tool
2. Check fuel trims at idle and at speed
3. Inspect the mass air flow sensor and intake for leaks
4. Inspect the oxygen sensor 1 bank 1 connector and wiring
5. Replace the oxygen sensor 1 bank 1 if it stays stuck
6. Clear the code and retest

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