What this code means

The upstream heated oxygen sensor on Bank 1 is not switching and indicates a persistent rich condition. The PCM detects the sensor is stuck indicating rich (low oxygen) and has reached its maximum lean correction limit.

Symptoms

• Check Engine Light
• Rich exhaust smell
• Black exhaust smoke
• Poor fuel economy
• Rough idle
• Fouled spark plugs

Common causes

• Leaking fuel injector Bank 1
• High fuel pressure (faulty regulator)
• Faulty O2 sensor stuck rich
• Saturated charcoal canister (EVAP purge issue)
• Coolant leak into combustion chamber

Diagnostic steps

1. Monitor O2 sensor on scan tool — should oscillate, not stay high
2. Check fuel pressure for over-pressure
3. Inspect spark plugs for fouling
4. Check for leaking injectors
5. Inspect for coolant consumption

Repair notes

Replace O2 sensor if stuck. Check fuel pressure regulator. Inspect for leaking injectors.

Other Powertrain codes on this vehicle