Technical Description of OBD-II Trouble Code
Generic: High Control Circuit for HO2S Heater (Sensor 2 in Bank 1)
Nissan: High voltage in the heater of oxygen sensor (HO2S) 2 in Bank 1
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code, which means it is applicable to OBD-II equipped vehicles, including Toyota, VW, Ford, Dodge, Honda, Chevrolet, Hyundai, Audi, Nissan, etc. The specific repair steps may vary depending on the model.
Oxygen sensors with a heating element are commonly used in modern engines. Heated Oxygen sensors (HO2S) are inputs that the PCM (Powertrain Control Module) uses to determine the oxygen content in the exhaust system.
The PCM primarily uses the information from the Bank 1,2 HO2S to monitor the efficiency of the catalytic converter. This sensor contains a heater element. In older vehicles without OBD II, an Oxygen sensor had only one wire, but now they typically have four wires: two for the oxygen sensor and two for the heater element. The oxygen sensor heater reduces the time required to achieve closed loop. The PCM controls the heater on-time. The PCM also continuously monitors the heater circuits for abnormal voltages or, in some cases, abnormal amperages.
Depending on the vehicle make, the Oxygen sensor heater is controlled in one of two ways. (1) The PCM directly controls the voltage feed to the heater, either directly or through a HO2S relay, and a ground is supplied from the vehicle’s common ground. (2) There is 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 that controls the ground side of the heater circuit. It is important to determine which type is present because the PCM activates the heater under various circumstances. If the PCM detects an abnormally high voltage condition on the heater circuit, P0038 may be triggered. This code only refers to the heating circuitry half of the Oxygen sensor.
Symptoms
Symptoms of a P0038 DTC may include:
There are unlikely to be any other symptoms.
Causes
Potential causes of a P0038 code include:
Possible Solutions
First, visually inspect the Bank 1, 2 HO2S (heated oxygen sensor) and its wiring harness. If there is any damage to the sensor or wiring, repair it as necessary. Check for bare wires where the wiring enters the sensor, as these can fatigue and cause shorts. Ensure that the wiring is routed away from the exhaust. Repair the wiring or replace the sensor as needed.
If everything appears to be in order, unplug the Bank 1,2 HO2S and verify that there is 12 volts B+ present with the key on engine off (or that ground is present, depending on the system). Verify that the heater control (ground) circuit is intact. If so, remove the o2 sensor and inspect it 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.
