Possible causes

– Faulty Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1
– Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 harness is open shorted
– Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 circuit poor electrical connection
– Heated Oxygen Sensor (H2OS) Bank 2 Sensor 1 fuse
– Faulty Engine Control Module (ECM)

Tech notes

The code means that there is a problem with the heater element circuit of the heated oxygen sensor. Water getting inside the heated oxygen sensor connector can caused the heated oxygen sensor fuse to blow, which is a very common problem for this type codes. Before replacing the sensor, check for the condition of the heated oxygen sensor fuse and connectors.

When is the code detected?

The P0051 is set when the ECM detects an excessively low voltage through the heated oxygen sensor heater circuit

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)

P0051 OLDSMOBILE Description

The Heated Oxygen (HO2S) bank 2 sensor 1 is threaded into the exhaust manifold. The sensor is equipped with a heater element to decrease the amount of time required to enter closed loop fuel control. The Engine Control Module (ECM) controls the heater by pulsing circuit 551 to ground. When the heater is commanded Off (circuit not grounded), the voltage level at the ECM should be high (ignition voltage). When the heater is commanded On (circuit grounded), the voltage level at the ECM should be low. The ECM heater feedback circuit uses a pull-up voltage (1.6-3.6 volts), which allows the ECM to individually differentiate between an open, short to ground or short to voltage.