P1157 - FAULT CODE - OBD2

POST UPDATED IN October, 2021

P1157 Code failures by brands

P1157 BUICK, CADILLAC, CHEVROLET, GMC: HO2S BANK 2 SENSOR 2 LEAN SYSTEM OR LOW VOLTAGE

Description of DTC code P1157

An Oxygen Sensor (HO2S) is a device that is used to adjust the air/fuel mixture. It also checks how efficient the TWC (Catalytic Converter) is. This type of sensor measures how much oxygen is present in the exhaust and sends this data to the ECM (Engine Control Module). For accurate readings, the oxygen sensor must reach the necessary temperature. For this reason, they have a heater that decreases the time required to reach that temperature.

The HO2S receives from the Engine Control Module 450mV reference. After starting the engine for the first time, the ECM activates the open-loop function and ignores the sensor voltages. When the Oxygen Sensor works at the required temperature, the ECM operates in a closed-loop, and the sensor sends a signal from 0 to 1,000mV.

The P1157 OBD2 fault code setting occurs when the ECM finds the voltages are excessively below the allowed values in the Oxygen Sensor 2 circuit of bank 2.

Symptoms of fault code P1157

Causes of OBD2 P1157

The P1157 OBDII diagnostic code is set for the following reasons:

  • The fuel system may not have enough pressure.
  • Possibly there are vacuum leaks in the motor.
  • Oxygen sensor cables or connectors may be damaged.
  • HO2S 2 may be in poor condition.
  • A fuel injector could be faulty.
  • The MAF sensor may be malfunctioning.

Possible solutions of the DTC code P1157

Consider these suggestions to solve the DTC P1157 OBD2 code:

  • By using an automotive scanner, check no DTCs are stored in addition to P1157. If there are codes that show Oxygen Sensor or Fuel System faults, diagnose them first.
  • With the engine running, and at operating temperature, connect the scanner to monitor the high signal circuit voltage of the O2 Sensor number 2 of bank 2. If the value obtained differs from that specified, check that it is not due to sensor contamination. Make the appropriate corrections.
  • Check for damage to the connectors or wires in the Oxygen Sensor circuit. If you do not discover any shortages in the electrical components, it could be a bad sensor.

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