DTC 0303

Front Heated Oxygen Sensors (0503: Right Bank) (0303: Left Bank)

COMPONENT DESCRIPTION
The front heated oxygen sensor is placed into the exhaust manifold. It detects the amount of oxygen in the exhaust gas compared to the outside air. The front heated oxygen sensor has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from approximately 1 V in richer conditions to 0 V in leaner conditions. The front heated oxygen sensor signal is sent to the ECM. The ECM adjusts the injection pulse duration to achieve the ideal air-fuel ratio. The ideal air-fuel ratio occurs near the radical change from 1 V to 0 V.

CONSULT REFERENCE VALUE IN DATA MONITOR MODE
Specification data are reference values.

ECM TERMINALS AND REFERENCE VALUE
Specification data are reference values, and are measured between each terminal and (25) (ECCS ground).

ON BOARD DIAGNOSIS LOGIC
Under the condition in which the front heated oxygen sensor signal is not input, the ECM circuits will read a continuous approximately 0.3 V. Therefore, for this diagnosis, the time that output voltage is within 200 to 400 mV range is monitored, and the diagnosis checks that this time is not inordinately long.

DIAGNOSTIC TROUBLE CODE CONFIRMATION PROCEDURE

CAUTION: Always drive vehicle at a safe speed.

NOTE: If "DIAGNOSTIC TROUBLE CODE CONFIRMATION PROCEDURE" has been previously conducted, always turn ignition switch "OFF" and wait at least 5 seconds before conducting the next test.

TESTING CONDITION:
Never raise engine speed above 3,600 rpm (A/T), 4,000 rpm (M/T) during the "DIAGNOSTIC TROUBLE CODE CONFIRMATION PROCEDURE". If the engine speed limit is exceeded, retry the procedure from step 2).

Always drive vehicle at a temperature of more than -10°C (14°F).

Before performing the following procedure, confirm that battery voltage is more than 11 V at idle.

OVERALL FUNCTION CHECK
Use this procedure to check the overall function of the front heated oxygen sensor circuit. During this check, a 1st trip DTC might not be confirmed.

DIAGNOSTIC PROCEDURE

Electrical Diagrams/Left Bank

Circuit Connectors/Left Bank

Electrical Diagrams/Right Bank

Circuit Connectors/Right Bank

COMPONENT INSPECTION
Front heated oxygen sensor

Without TOOLS
(1) Start engine and warm it up to normal operating temperature.
(2) Set voltmeter probes between ECM terminal (50) RH, (51) LH (sensor signal) and (25) (ECM ground).
(3) Check the following with engine speed held at 2,000 rpm constant under no load.

- Malfunction indicator lamp goes on more than 5 times within 10 seconds in Diagnostic Test Mode II (FRONT HEATED OXYGEN SENSOR MONITOR).
- The maximum voltage is over 0.6 V at least one time.
- The minimum voltage is below 0.35 V at least one time.
- The voltage never exceeds 1.0 V.