Possible Cause

NOTE:  The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.

• Rear A/F sensor (bank 1, sensor 1) malfunction/slow response
• Rear A/F sensor (bank 1, sensor 1) circuit range/performance
• Fuel system too lean
• Fuel system too rich
• Rear secondary HO2S (bank 1, sensor 2) circuit signal stuck lean
• Rear secondary HO2S (bank 1, sensor 2) circuit high voltage
• Rear secondary HO2S (bank 1, sensor 2) slow response
• Misfire
• Exhaust system failure (exhaust gas leak)