P0043 B2S1 Heated Oxygen Sensor (HO3S) Heater Control Circuit Low

P0043 B2S1 Heated Oxygen Sensor (HO3S) Heater Control Circuit Low

OBD-II DTC Datasheet

Low signal in the oxygen sensor heater control circuit (block 2, sensor 1)

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, Toyota, Mazda, Mitsubishi, Lexus, Infiniti, VW, etc. Specific repair steps may differ depending on the brand / model.

Heated Oxygen Sensors (HO2S) are inputs used by the PCM (Powertrain Control Module) to detect the amount of oxygen in the exhaust system. Bank 1 sensor 3 refers to the third sensor on bank 1. Bank 1 is the side of the engine that contains cylinder #1 (inline engines have only one bank). The PCM uses information from the Bank 1 #3 HO2S sensor primarily to monitor the efficiency of the catalytic converter. An integral part of this sensor is the heating element.

The PCM controls this heater to bring the sensor up to operating temperature. This allows the engine to enter the closed loop more quickly and reduces cold start emissions. The PCM continuously monitors the heater circuits for abnormal voltages or, in some cases, even amperages. Depending on the make of the vehicle, the oxygen sensor heater is controlled in one of two ways. One way is for the PCM to directly control the voltage supply to the heater, either directly or through an oxygen sensor (HO2S) relay, and the ground is supplied from the vehicle's common ground. Another way is 12V battery power with a fuse (B+) that supplies 12V to the heater element any time the ignition is on and the heater is controlled by a driver in the PCM that controls the ground 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 low voltage on the heater circuit, P0043 may set.

symptoms

Symptoms of a P0043 trouble code may include:

• Malfunction Indicator Lamp (MIL) Illumination
• Most likely, there will be no other symptoms.

reasons

Possible causes of DTC P0043 may include:

• Sensor No. 3 on block 1 of the oxygen sensor heating element is out of order
• Physical damage to the heated oxygen sensor has occurred.
• The control circuit (or voltage supply, depending on the system) is shorted to ground
• PCM oxygen sensor heater driver defective

Possible solutions

Visually inspect bank 1, HO3S 2, and wiring harness. If there is any damage to the sensor or any damage to the wiring, repair / replace as needed. Make sure the wiring is routed away from the exhaust pipe. If ok, disconnect row 1,3 HO2S and check for 12 volts B + with 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.

Related DTC discussions

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