Audi P1111: O2 Control (Bank 1) System Too Lean

What Does The Audi P1111 Code Mean?

Engine started, battery voltage must be at least 11.5v, all electrical components must be off, the ground between the engine and the chassis must be well connected, the exhaust system must be properly sealed between the catalytic converter and the cylinder head, and the oxygen sensor heater for oxygen sensor before the catalytic converter must be properly functioning. The ECM detected a measurement on the O2 sensor circuit that was outside the parameters to function properly.

Note: For resistance testing of sensor heating, oxygen sensor should be cooled to ambient temperature. High temperatures at oxygen sensor may lead to inaccurate measurements.

Note: When an O2S malfunction (P0131 to P0414) is also stored with this malfunction, the O2S malfunction(s) should be repaired first.

What Are The Potential Causes Of The Audi P1111 Code?

• Oxygen sensor (before catalytic converter) is faulty
• Oxygen sensor (behind catalytic converter) is faulty
• Oxygen sensor heater (before catalytic converter) is faulty
• Oxygen sensor heater (behind catalytic converter) is faulty
• Circuit wiring has a short to power or ground
• Engine Component Power Supply Relay is faulty
• E-box fuses for oxygen sensor are faulty
• Leaks present in the exhaust manifold or exhaust pipes
• HO2S signal wire and ground wire crossed in connector
• HO2S element is fuel contaminated or has failed
• ECM has failed

Recommended Parts

Below are some recommended auto parts to help you address the trouble code affecting your vehicle and get it running smoothly again:

Note: During the purchasing process, please check carefully whether the part you want to buy fits your car!

Reference Sources

• Audi of Ameria, 2002, Technical Service Bulletin – Diagnosis off Driveability Complaints on Turbo Charged Engines.
• Audi A4 Avant 95-01 Service Repair Manual, page 37.