P0138
Component Description
The rear heated oxygen sensor (Rear HO2S), after three way catalyst, monitors the oxygen level in the exhaust gas. Even if switching characteristics of the front heated
oxygen sensor are shifted, the air fuel ratio is controlled to stoichiometric, by the signal from the rear heated oxygen sensor.
This sensor is made of ceramic zirconia. The zirconia generates voltage from approximately 1 V in richer conditions to 0 V in leaner conditions.
Under normal conditions the rear heated oxygen sensor is not used for engine control operation.
CONSULT-II 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 48 (ECM ground).
ON BOARD DIAGNOSIS LOGIC
The rear heated oxygen sensor has a much longer switching time between rich and lean than the front heated oxygen sensor. 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 whether the maximum voltage of the sensor is sufficiently
high during various driving conditions such as fuel-cut.
DTC CONFIRMATION PROCEDURE
NOTE: If "DTC Confirmation Procedure" has been previously conducted, always turn ignition switch "OFF" and wait at least 5 seconds before conducting the next test.
TESTING CONDITION: Open engine hood before conducting following procedure.
With CONSULT-II
1. Start engine and warm it up to normal operating temperature.
2. Turn ignition switch "OFF" and wait at least 5 seconds.
3. Turn ignition switch "ON".
4. Select "DATA MONITOR" mode with CONSULT-II.
5. Make sure that "COOLAN TEMP/S" indicates more than 70 °C (158 °F).
6. Select "RR O2 SEN-B1 P0138" of "REAR O2 SENSOR" in "DTC WORK SUPPORT" mode with CONSULT-II.
7. Start engine and follow the instruction of CONSULT-II.
8. Make sure that "OK" is displayed after touching "SELF-DIAG RESULTS".
If NG is displayed, refer to "Diagnostic Procedure".
If "CANNOT BE DIAGNOSED" is displayed, perform the following.
a. Stop engine and cool down until "COOLAN TEMP/S" indicates less than 70 °C (158 °F).
b. Turn ignition switch "ON".
c. Select "DATA MONITOR" mode with CONSULT-II.
d. Start engine.
e. Return to step 6 again when the "COOLAN TEMP/S" reaches to 70 °C (158 °F).
Overall Function Check
Use this procedure to check the overall function of the rear heated oxygen sensor circuit. During this check, a 1st trip DTC might not be confirmed.
With Generic Scan Tool
1. Start engine and drive vehicle at a speed of 70 KPH (43 MPH) for 2 consecutive minutes.
2. Stop vehicle with engine running.
3. Set voltmeter probes between ECM terminals 63 (Rear heated oxygen sensor signal) and engine ground.
4. Check the voltage when revving engine 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 0.48 V at least once during this procedure.
If the voltage can be confirmed in step 4, step 5 is not necessary.
5. keep vehicle at idling for 10 minutes, then check the voltage. Or check the voltage when coasting from 80 KPH (50 MPH) in 3rd gear position (M/T), D position with "OD" OFF (A/T).
The voltage should be above 0.48 V at least once during this procedure.
6. If NG, go to "Diagnostic Procedure".
EC-RRO2-01:
EC-RRO2-01 - Connector Views:
WIRING DIAGRAM
M1,M2,M3,M4,M5,B1,E71,E72,E73 Connector Views:
Step 1:
Step 2:
Step 3:
Step 4:
Step 5:
Step 6:
Step 7:
DIAGNOSTIC PROCEDURE
Component Inspection
With CONSULT-II
1. Start engine and drive vehicle at a speed of more than 70 KPH (43 MPH) for 2 consecutive minutes.
2. Stop vehicle with engine running.
3. Select "FUEL INJECTION" in "ACTIVE TEST" mode, and select "RR O2 SEN-B1" as the monitor item with CONSULT-II.
4. Check "RR O2 SEN-B1" at idle speed when adjusting "FUEL INJECTION" to ±25%.
"RR O2 SEN-B1" should be above 0.48 V at least once when the "FUEL INJECTION" is +25%.
"RR O2 SEN-B1" should be below 0.43 V at least once when the "FUEL INJECTION" is -25%.
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.
- Before installing new oxygen sensor, clean exhaust system threads using Oxygen Sensor Thread Cleaner tool J-43897-18 or J-43897-12 and approved anti-seize lubricant.
Without CONSULT-II
1. Start engine and drive vehicle at a speed of 70 KPH (43 MPH) for 2 consecutive minutes.
2. Stop vehicle with engine running.
3. Set voltmeter probes between ECM terminals 63 (Rear heated oxygen sensor signal) and engine ground.
4. Check the voltage when revving 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 0.48 V at least once.
If the voltage is above 0.48 V at step 4, step 5 is not necessary.
5. Check the voltage when revving 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 KPH (50 MPH) in 3rd gear position (M/T), D position with "OD" OFF (A/T). The voltage should be below 0.43 V at least once.
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.
- Before installing new oxygen sensor, clean exhaust system threads using Oxygen Sensor Thread Cleaner tool J-43897-18 or J-43897-12 and approved anti-seize lubricant.