P0043

DTC P0043 OXYGEN SENSOR HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 3)

HINT:
- These DTCs are recorded when a heated oxygen sensor heater circuit is not working properly.
- DTCs P0043 and P0044 have been added to meet the requirement for Partial Zero Emission Vehicle (PZEV).
- Sensor 2 is the sensor positioned in the 2nd location from the engine assembly, located after the front catalyst.
- Sensor 3 is the sensor positioned in the 3rd location from the engine assembly, located after the rear catalyst.

CIRCUIT DESCRIPTION

DTC Detection Condition:

This sensor (heated oxygen sensor 3) is similar to the heated oxygen sensor 2, only difference between the two sensors is that this is not used to regulate the air-fuel ratio. The sensor is located after the rear catalyst (hydrocarbon (HC) absorptive catalyst) only to detect the deterioration in the catalyst.

In a circuit inside the ECM, impedance* of the heated oxygen sensor 3 is measured by the ECM. The ECM determines that there is a malfunction in the sensor when the measured impedance deviates from the standard range.

*: The effective resistance in an alternating current electrical circuit.






HINT: The ECM provides a pulse width modulated control circuit to adjust current through the heater. The heated oxygen sensor heater circuit uses a relay on the B+ side of the circuit.

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Conditions:

Typical Malfunction Thresholds:

Component Operating Range:

Monitor Result (Mode 06):

The sensing portion of the heated oxygen sensor has a zirconia element which is used to detect oxygen concentration in the exhaust. If the zirconia element is at the proper temperature and difference of the oxygen concentration between the inside and outside surface of sensor is large, the zirconia element will generate voltage signals. In order to increase the oxygen concentration detecting capacity in the zirconia element, the ECM supplements the heat from the exhaust with heat from a heating element inside the sensor. When current in the sensor is out of the standard operating range, the ECM interprets this as a fault in the heated oxygen sensor and sets a DTC.

Example:
The ECM will set a high current DTC if the current in the sensor is more than 2 A when the heater is OFF. Similarly, the ECM will set a low current DTC if the current is less than 0.25 A when the heater is ON.

Wiring Diagram:

Step 1:

Step 2 - 3:

Step 4:

INSPECTION PROCEDURE

HINT: Read freeze frame data using the hand-held tester or the OBD II scan tool. Freeze frame data records the engine conditions when the malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.