Technical Description of OBD-II Trouble Code
Generic: Low Control Circuit for HO2S Heater (Bank 1 Sensor 2)
Nissan: Low voltage in heater of oxygen sensor (HO2S) 2 Bank 1
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to OBD-II equipped vehicles, including Toyota, VW, Ford, Dodge, Honda, Chevrolet, Hyundai, Audi, Acura, etc. The specific repair steps may vary depending on the model.
Heated Oxygen sensors (HO2S) are inputs used by the PCM (Powertrain Control Module) to determine the oxygen content in the exhaust system. Bank 1, sensor 2 refers to the second sensor at the back of bank 1. The PCM utilizes the information obtained from the Bank 1,2 HO2S primarily to monitor the efficiency of the catalytic converter. The sensor includes a heater element.
The PCM controls this heater to warm up the sensor to its operating temperature. This enables the engine to enter closed loop faster and reduces emissions during cold startup. The PCM continuously monitors the heater circuits for abnormal voltages or, in some cases, even amperages. Depending on the vehicle make, the Oxygen sensor heater is controlled in one of two ways. One way is that the PCM directly controls the voltage feed to the heater either directly or via a HO2S relay, and a ground is supplied from the vehicle’s common ground. The other way involves a fused 12 volt Battery feed (B+) that supplies 12 volts to the heater element whenever the ignition is on, and the control of the heater is done by a driver in the PCM which controls the ground side of the heater circuit.
Determining which one is present is important because the PCM activates the heater under various circumstances. If the PCM detects an abnormally low voltage condition on the heater circuit, P0037 may be set.
Symptoms
Symptoms of a P0037 DTC may include:
Causes
Potential causes of a P0037 trouble code may include:
Possible Solutions
Perform a visual inspection of the Bank 1, 2 HO2S and wiring harness. If there is any damage to the sensor or wiring, repair or replace as necessary. Ensure that the wiring is routed away from the exhaust. If everything appears to be in order, unplug the Bank 1, 2 HO2S and check for the presence of 12 volts B+ with the key on engine off (or the presence of ground, depending on the system).
Verify that the heater control (ground) circuit is intact. If so, remove the o2 sensor and inspect for damage. If you have access to resistance specifications, you can use an Ohmmeter to perform a resistance test of the heater element. Infinite resistance indicates an open in the heater. Replace the o2 sensor as necessary.
