P1138 BUICK, CADILLAC, CHEVROLET, GMC - HO2S BANK 1 SENSOR 2 RICH OR HIGH VOLTAGE
POST UPDATED IN January, 2023
P1138 BUICK, CADILLAC, CHEVROLET, GMC - HO2S BANK 1 SENSOR 2 RICH OR HIGH VOLTAGE
An HO2S (Oxygen Sensor) is a device whose function is to take readings of the oxygen in the exhaust. Then, it compares these readings to use the data for fuel control and subsequent monitoring of the TWC (Catalyst). The operation of this type of sensor depends on the temperature, which defines its readings. That is why they are equipped with a heater that reduces the time for the sensor to reach the necessary temperature for a good performance.
The Oxygen sensors usually receive 450mV of reference from the ECM (Engine Control Module). When the engine ignition occurs, this module goes into an open circuit and ignores the HO2S voltage. At operating temperature, it goes into a closed circuit and the voltage produced by it changes from 0 to 1,000mV.
Although it is a specific code, the setting of the P1138 OBDII fault code indicates in many cases that the ECM has found a voltage in the circuit of the O2 Sensor number 2 of bank 1, this exceeds the limit established by the manufacturer.
The P1138 OBD2 diagnostic code is set due to:
To troubleshoot DTC P1138 OBD2, try this: