Ford P1157 OBD-II Trouble Code Definition:
P1157 Lack Of HO2S22 Switch – Sensor Indicates Lean
P1157 Ford OBD-II Trouble CodeDescription:
The downstream HO2Ss are forced rich and lean and monitored by the PCM. The test fails if the PCM does not detect the output of the HO2S in a calibrated amount of time.