P0044 High signal level in the heater control circuit of the oxygen sensor (HO2S) (bank 1, sensor 3)
Content
P0044 High signal level in the heater control circuit of the oxygen sensor (HO2S) (bank 1, sensor 3)
OBD-II DTC Datasheet
HO2S Heater Control Circuit High (Bank 1 Sensor 3)
What does this mean?
This Diagnostic Trouble Code (DTC) is a generic transmission code, which means it applies to OBD-II equipped vehicles, including but not limited to Nissan, Mitsubishi, Mazda, Subaru, Toyota, VW, etc. Although generic, specific repair steps may differ depending on the brand / model.
Oxygen sensors with a heating element are widely used in modern engines. Heated oxygen sensors (HO2S) are inputs used by the PCM (Powertrain Control Module) to detect the oxygen content in the exhaust system.
The PCM uses information from Bank 1, HO3S # 2, primarily to monitor the efficiency of the catalytic converter. An integral part of this sensor is the heating element. Whereas in cars before OBD II, the oxygen sensor was a single-wire sensor, they are now most often four-wire sensors: two dedicated to the oxygen sensor and two dedicated to the heating element. The oxygen sensor heater basically reduces the time it takes to reach a closed loop. The PCM monitors the time to turn on the heater. The PCM also continuously monitors the heater circuits for abnormal voltage or, in some cases, even abnormal current.
The oxygen sensor heater is controlled in one of two ways, depending on the vehicle brand. (1) The PCM directly controls voltage to the heater, either directly or through the oxygen sensor (HO2S) relay, and ground is supplied from the vehicle common ground. (2) There is a 12 volt battery fuse (B +) that supplies 12 volts to the heating element anytime the ignition is turned on, and the heater is controlled by a driver in the PCM that controls the grounded side of the heater circuit. ... Figuring out which one you have is important because the PCM will activate the heater under various circumstances.
If the PCM detects an abnormally high voltage on the heater circuit, P0044 may set. This code only applies to half of the oxygen sensor heating circuit.
symptoms
Symptoms of a P0044 trouble code may include:
- MIL Illumination (Malfunction Indicator Lamp)
Most likely, there will be no other symptoms.
reasons
Possible causes of a P0044 code include:
- Defective heated oxygen sensor # 3 on row 1.
- Open in Heater Control Circuit (12V PCM Controlled Systems)
- Short to B + (battery voltage) in the heater control circuit (12V PCM controlled systems)
- Open Ground Circuit (12V PCM Controlled Systems)
- Short to ground in the heater control circuit (on PCM grounded systems)
Possible solutions
First, visually inspect the third post-engine HO2S on Bank 1 and its wiring harness. If there is any damage to the sensor or any damage to the wiring, fix it as needed. Check for exposed wires where wiring enters the sensor. This often leads to fatigue and short circuits. Make sure the wiring is routed away from the exhaust pipe. Repair the wiring or replace the sensor if necessary.
If ok, disconnect the bank 3 # 1 HO2S and verify that 12 volts B + is present with the engine off (or ground, depending on the system). Verify heater control circuit (ground) is intact. If so, remove the O2 sensor and inspect it for damage. If you have access to resistance characteristics, you can use an ohmmeter to test the resistance of the heating element. Infinite resistance indicates an open circuit in the heater. Replace the oxygen sensor if necessary.
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