P0037 CADILLAC HO2S12 Heater Control Circuit Low Voltage

Possible causes

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

Tech description

The code means that there is a problem with the heater element circuit of the heated oxygen sensor. The control module monitors how long it take the sensor to warm up and start sending an adequate signal. The code is triggered when the sensor is taking too long to warm up. Water getting inside the heated oxygen sensor connector can caused the heated oxygen sensor fuse to blow. Before replacing the sensor, check for the condition of the heated oxygen sensor fuse and connectors. If the sensor and connector are OK, replacing the O2 Sensor 1 usually takes care of the problem

When is the obd code mean?

The P0037 is set when the PCM detects a ground in the heater circuits of the HO2S when the heater is commanded off

Symptoms

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

P0037 CADILLAC 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 Powertrain Control Module (PCM).

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

The PCM 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.