Troubleshooting

DTC P2195 OXYGEN SENSOR SIGNAL STUCK LEAN (BANK 1 SENSOR 1)

CIRCUIT DESCRIPTION

DTC Detection Condition:

To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three-way catalytic converter is used. But for the most efficient use of the three-way catalytic converter, the air-fuel ratio must be precisely controlled so that it is always close to the stoichiometric air-fuel ratio.

The heated oxygen sensor has the characteristic whereby its output voltage changes suddenly in the vicinity of the stoichiometric air-fuel ratio. This is used to detect the oxygen concentration in the exhaust gas and provide the ECM with feedback control the air-fuel ratio.

When the air-fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases. And the heated oxygen sensor informs the ECM of the LEAN condition (small electromotive force: <0.45 V).

When the air-fuel ratio is RICHER than the stoichiometric air-fuel ratio, the oxygen concentration in the exhaust gas is reduced. And the heated oxygen sensor informs the ECM of the RICH condition (large electromotive force: > 0.45 V). The ECM judges by the electromotive force from the heated oxygen sensor whether the air-fuel ratio is RICH or LEAN and controls the injection time accordingly. However, if the malfunction of the oxygen sensor causes an output of abnormal electromotive force, the ECM becomes unable to perform the accurate air-fuel ratio control.

The main heated oxygen sensors include a heater which heats the zirconia element. The heater is controlled by the ECM. When the intake air volume is low (the temperature of the exhaust gas is low), current flows to the heater in order to heat the sensor for the accurate oxygen concentration detection.


HINT:
- Bank 1 refers to the bank that includes cylinder No.1.
- Bank 2 refers to the bank that does not include cylinder No.1.
- Sensor 1 refers to the sensor closest to the engine body.
- The heated oxygen sensor's output voltage and the short-term fuel trim value can be read using the OBD II scan tool or the hand-held tester.

Wiring Diagram:

CONFIRMATION DRIVING PATTERN




a. Connect the hand-held tester to the DLC3.
b. Switch the hand-held tester from the "normal mode" to "check mode".
c. Start the engine and let the engine idle for 100 seconds or more.
d. Drive the vehicle at 40 km/h (24 mph) or more for 20 seconds or more.
e. Let the engine idle for 20 seconds or more.
f. Let the engine idle for 30 seconds.

HINT: If a malfunction exists, the MIL will light up during step (f).

NOTE: If the conditions in this test are not strictly followed, detection of the malfunction will be impossible.
If you do not have the hand-held tester, turn the ignition switch OFF after performing steps (c) to (f), then perform steps (c) to (f) again.

Step 1 - 2:

Step 3 - 4:

Step 5 - 8:

INSPECTION PROCEDURE

NOTE: If the vehicle is short of fuel, the air-fuel ratio becomes LEAN and DTC P0125 will be recorded, and the check engine warning light then comes on.

HINT: Read freeze frame data using hand-held tester or OBD II scan tool, as freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio lean or rich, etc. at the time of the malfunction.