Lack Of HO2S21 Switch - Sensor Indicates Lean

Where it lives

For P1151, the description names the sensor as the part involved.

Check these first

• An upstream oxygen sensor bank 2 that reads lean and will not switch
• A vacuum leak leaning bank 2
• Fuel pressure that is too low
• A dirty or faulty mass air flow sensor
• A leaking fuel injector or fuel pressure regulator

What to do next

1. Read upstream oxygen sensor bank 2 voltage
2. Check fuel pressure against specification
3. Smoke test the intake for vacuum leaks
4. Inspect the mass air flow sensor and intake
5. Replace the upstream oxygen sensor bank 2 if it stays lean and lazy
6. Clear the code and retest

Look up another code