Audi
Type:
    Powertrain - Manufacturer Controlled DTC - Manufacturer Controlled
Description:
    Long term fuel trim 1, Bank 1 - below lean limit
Cause:
    Fuel pressure/pump, injectors, intake/exhaust leak, HO2S

Ford
Type:
    Powertrain - Manufacturer Controlled DTC - Manufacturer Controlled
Description:
    Lack of HO2S Switches, Sensor at Lean Limit Conditions
Cause:
    Engine running in closed loop, then the PCM detected that the HO2S-21 signal did not switch because the fuel control system is at its lean limit

Mazda
Type:
    Powertrain - Manufacturer Controlled DTC - Manufacturer Controlled
Description:
    Heated oxygen sensor (HO2S) lean mixture indicated
Cause:
    Wiring, HO2S, fuel pressure, fuel system, mechanical fault, ECM

Subaru
Type:
    Powertrain - Manufacturer Controlled DTC - Manufacturer Controlled
Description:
    Heated oxygen sensor (HO2S) voltage high
Cause:
    Wiring, HO2S, ECM

Volkswagen
Type:
    Powertrain - Manufacturer Controlled DTC - Manufacturer Controlled
Description:
    Long term fuel trim below lean limit
Cause:
    Fuel pressure/pump, injectors, intake/exhaust leak, HO2S