California Models

DESCRIPTION
The rear heated oxygen sensor is placed into the front exhaust tube. It detects the amount of oxygen in the exhaust gas compared to the outside air. The rear heated oxygen sensor has a closed-end tube made of ceramic zirconia. The zirconia generates voltage from approximately 1 Volt in richer conditions to O Volts in leaner conditions. The rear 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 Volt to O Volts.




ON-BOARD DIAGNOSIS LOGIC
The rear heated oxygen sensor has a much longer switching time between rich and lean than the front oxygen sensor *1. The oxygen storage capacity before the three way catalyst causes the longer switching time. To judge the malfunctions of rear heated oxygen sensor, ECM monitors the sensor's voltage value and the switching response during the various driving condition such as fuel-cut.

*1: Front heated oxygen sensor (California models)
Front oxygen sensor (Non-California models)

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

WITH CONSULT
1. Start engine and warm it up sufficiently.




2. Select "FUEL INJECTION" in "ACTIVE TEST" mode, and select "RR 02 SENSOR" as the monitor item with CONSULT.
3. Check "RR 02 SENSOR" at idle speed when adjusting "FUEL INJECTION" to ±25%.

"RR O2 SENSOR" should be above O.48V (California models), O.60V (Non-California models) at least once when the "FUEL INJECTION" is +25%.
"RR O2 SENSOR" should be below O.43V (California models), O.55V (Non-California models) at least once when the "FUEL INJECTION" is -25%.

OR

WITH NO TOOLS
1. Start engine and warm it up sufficiently.




2. Set voltmeter probes between ECM terminals (52) (sensor signal) and (43) (engine ground).




3. Check the voltage when racing up to 4,000 rpm under no load at least 10 times.
(depress and release accelerator pedal as soon as possible)
The voltage should be above O.48 Volts at least once. If the voltage is above O.48 Volts at step 3, step 4 is not necessary.
4. Check the voltage when racing up to 6,000 rpm under no load. Or keep vehicle at idling for 10 minutes, then check the voltage. Or check the voltage when coasting from 80 km/h (50 MPH) in 3rd gear position. The voltage should be below O.43 Volts at least once.




WIRING DIAGRAM




DIAGNOSTIC PROCEDURE

COMPONENT INSPECTION
Rear heated oxygen sensor heater




1. Check resistance between terminals (2) and (3).

Resistance: 2.3 - 4.3 Ohms at 25°C (77°F)

2. Check continuity.




If NG, replace the rear heated oxygen sensor.

CAUTION:
- Discard any heated oxygen sensor which has been dropped from a height of more than 0.5 m (19.7 in) onto a hard surface such as a concrete floor; use a new one.