P1272
DTC P1272 A/F SENSOR
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
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. Start engine and warm it up to normal operating temperature.
2. Select "A/F SEN1 (B1)" in "DATA MONITOR" mode with CONSULT-II.
3. Check "A/F SEN1 (B1)" indication.
If the indication is constantly approx. 4.5 V, go to "Diagnostic Procedure" below.
If the indication is not constantly approx. 4.5 V, go to next step.
4. Select "A/F SEN1 (B1) P1278/P1279" of "A/F SEN1" in "DTC WORK SUPPORT" mode.
5. Touch "START".
6. 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.
7. 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.
8. Make sure that "TESTING" changes to "COMPLETED".
If "TESTING" changed to "OUT OF CONDITION", retry from step 6.
9. Touch "BACK" and "MODE", then select "SELF-DIAG RESULT" mode. If P1272 is displayed, go to "Diagnostic Procedure" below. If another DTC is displayed, go to the corresponding Diagnostic Procedure.
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. Start engine and warm it up to normal operating temperature.
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):
