P1279
DTC P1279 A/F SENSOR 1
Component Description
The A/F sensor 1 is a planar dual-cell limit current sensor. The sensor element of the A/F sensor 1 is the combination of a Nernst concentration cell (sensor cell) with an oxygen-pump cell, which transports ions. It has a heater in the element.
The sensor is capable of precise measurement lambda = 1, but also in the lean and rich range. Together with its control electronics, the sensor outputs a clear, continuous signal throughout a wide lambda range (0.7 < lambda < air).
The exhaust gas components diffuse through the diffusion gap at the electrode of the oxygen pump and Nernst concentration cell, where they are brought to thermodynamic balance.
An electronic circuit controls the pump current through the oxygen pump cell so that the composition of the exhaust gas in the diffusion gap remains constant at lambda = 1. Therefore, the A/F sensor 1 is able to indicate air-fuel ratio by this pumping of current. In addition, a heater is integrated in the sensor to ensure the required operating temperature of 700 - 800 °C (1,292 - 1,472 °F).
CONSULT-II Reference Value in Data Monitor Mode
On Board Diagnosis Logic
To judge the malfunction of air fuel ratio (A/F) sensor 1, this diagnosis measures response time of the A/F signal computed by ECM from the air fuel ratio (A/F) sensor 1 signal. The time is compensated by engine operating (speed and load), fuel feedback control constant, and the air fuel ratio (A/F) sensor 1 temperature index. Judgment is based on whether the compensated time (the A/F signal cycling time index) is inordinately long or not.
DTC Confirmation Procedure
CAUTION: Always drive vehicle at a safe speed.
NOTE: If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at least 10 seconds before conducting the next test.
TESTING CONDITION:
Before performing the following procedure, confirm that battery voltage is more than 11 V at idle.
WITH CONSULT-II
1. Perform EC-92, "Idle Air Volume Learning". Idle Air Volume LearningMake sure that "CMPLT" is displayed on CONSULT-II screen.
If "INCMP" is displayed, follow the instruction for Idle Air Volume Learning.
2. Select "A/F SEN1 (B1) P1278/P1279" of "A/F SEN1" in "DTC WORK SUPPORT" mode.
3. Touch "START".
4. When the given conditions are met, "TESTING" will be displayed on the CONSULT-II screen.
If "TESTING" is not displayed after 20 seconds, retry from step 2.
5. Following the instructions of CONSULT-II screen, set D position with "OD" OFF (A/T) or 3rd position (M/T) and release accelerator pedal fully.
6. Make sure that "TESTING" changes to "COMPLETED".
If "TESTING" changed to "OUT OF CONDITION", retry from step 6.
7. Make sure that OK is displayed after touching "SELF-DIAG RESULT".
If NG is displayed, go to "Diagnostic Procedure" below.
Overall Function Check
Use this procedure to check the overall function of the A/F sensor 1 circuit. During this check, a 1st trip DTC might not be confirmed.
WITH GST
1. Perform EC-92, "Idle Air Volume Learning". Idle Air Volume LearningMake sure the result is OK. If NG, follow the instruction for Idle Air Volume Learning.
2. Drive the vehicle at a speed of 80 km/h (50 MPH) for a few minutes in D position with "OD" OFF (A/T) or 3rd position (M/T).
NOTE: Keep the accelerator pedal as steady as possible during the cruising.
3. Set D position with "OD" ON (A/T) or 4th position (M/T), then release the accelerator pedal fully until the vehicle speed decreases to 50 km/h (30 MPH).
NOTE: Never apply brake during releasing the accelerator pedal.
4. Repeat steps 2 to 3 five times.
5. Stop the vehicle and turn ignition switch OFF.
6. Wait at least 10 seconds and restart engine.
7. Repeat steps 2 to 3 five times.
8. Stop the vehicle and connect GST to the vehicle.
9. Make sure that no DTC is displayed.
If the DTC is displayed, go to "Diagnostic Procedure" below.
EC-A/F-01:
Wiring Diagram
Diagnostic Procedure
Diagnostic Procedure (Steps 1 - 2):
Diagnostic Procedure (Steps 3 - 4):
