P0042 AUDI HO2S Heater Control Circuit Bank 1 Sensor 3

Possible causes

– Faulty Heated Oxygen Sensor (H2OS) Bank 1 Sensor 3
– Heated Oxygen Sensor (H2OS) Bank 1 Sensor 3 is open shorted to ground
– Heated Oxygen Sensor (H2OS) Bank 1 Sensor 3 poor electrical connection
– Heated Oxygen Sensor (H2OS) Bank 1 Sensor 3 fuse
– Faulty Engine Control Module (ECM)

Tech description

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.

HO2S Heater Control Circuit Bank 1 Sensor 3 is the generic definition for the P0042; however your vehicle’s manufacturer may have a different definition and information for the P0042 code.

When is the obd code mean?

The P0042 is set when the ECM detects an open or shorted to ground condition on the heated oxygen sensor heater circuit

Symptoms

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

P0042 AUDI OBD Code Description

Oxygen Sensors (O2S) or Heated Oxygen Sensors (HO2S) need to reach a minimum operating temperature of 750 degrees F to produce an accurate voltage signal. The faster the heated oxygen sensor reaches that temperature the faster the sensor will start sending an accurate signal to the Engine Control Module (ECM).

In order to achieve the require temperature, a heater element is included inside the heated oxygen sensor. The ECM controls the heated oxygen sensor heater element based on signals from the engine coolant temperature and engine load. The ECM controls the heater element circuit by allowing current flow to ground.

The ECM monitors the voltage signal received through the heater element circuit and determines the state of the circuit by comparing the voltage detected with the factory specifications.