P2238

DTC P2238 Oxygen (A/F) Sensor Pumping Current Circuit Low (Bank 1 Sensor 1)
DTC P2239 Oxygen (a/F) Sensor Pumping current circuit High (Bank 1 Sensor 1)
DTC P2252 Oxygen (A/F) Sensor Reference Ground Circuit Low (Bank 1 Sensor 1)
DTC P2253 Oxygen (A/F) Sensor Reference Ground Circuit High (Bank 1 Sensor 1)

HINT: Although the title (DTC description) says "oxygen sensor", this DTC is related to the "A/F sensor".

DESCRIPTION

DTC Detection Condition:

The Air-Fuel ratio (A/F) sensor provides output voltage* approximately equal to the existing air-fuel ratio. The A/F sensor output voltage is used to provide feedback for the ECM to control the air-fuel ratio. With the A/F sensor output, the ECM can determine deviation from the stoichiometric air-fuel ratio and control proper injection time. If the A/F sensor is malfunctioning, the ECM is unable to accurately control air-fuel ratio.

The A/F sensor is equipped with a heater which heats the zirconia element. The heater is also controlled by the ECM. When the intake air volume is low (the temperature of the exhaust gas is low), current flows to the heater to heat the sensor to facilitate detection of accurate oxygen concentration.

The A/F sensor is a planar type. Compared to a conventional type, the sensor and heater portions are narrower. Because the heat of the heater is conducted through the alumina to zirconia (of the sensor portion), sensor activation is accelerated.

To obtain a high purification rate of the CO, HC and NOx components of the exhaust gas, a three-way catalytic converter is used. The converter is most efficient when the air-fuel ratio is maintained near the stoichiometric air-fuel ratio.
*: The voltage value changes on the inside of the ECM only.

MONITOR DESCRIPTION

Monitor Strategy:

Typical Enabling Condition:

Typical Malfunction Thresholds:

The air-fuel ratio (A/F) sensor varies its voltage output in proportion to the air-fuel ratio. If impedance (alternating current resistance) or voltage output of the sensor deviates greatly from the standard, the ECM determines that an open or short is in the A/F sensor circuit.

HINT: Intelligent tester only:
It is possible that the malfunctioning area can be found using the ACTIVE TEST A/F CONTROL operation. The A/F CONTROL operation can determine if the A/F sensor, heated oxygen sensor or other potential trouble areas are malfunctioning or not.

1. Perform the ACTIVE TEST A/F CONTROL operation.

HINT: The A/F CONTROL operation lowers the injection volume by 12.5% or increases the injection volume by 25%.

a. Connect the intelligent tester to the DLC3 on the vehicle.
b. Turn the ignition switch ON.
c. Warm up the engine by running the engine at 2,500 rpm for approximately 90 seconds.
d. Enter the following menus: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
e. Perform the A/F CONTROL operation with the engine idle (press the right or left button).

Result:
A/F sensor reacts in accordance with increase and decrease of injection volume:
+25% -> RICH output: Less than 3.0 V
-12.5% -> LEAN output: More than 3.35 V

Heated oxygen sensor reacts in accordance with increase and decrease of injection volume:
+25% -> RICH output: More than 0.55 V
-12.5% -> LEAN output: Less than 0.4 V

NOTE: The A/F sensor output has a few seconds of delay and the heated oxygen sensor output has about 20 seconds of delay at maximum.







The following A/F CONTROL procedure enables the technician to check and graph the voltage outputs of both the A/F sensor and the heated oxygen sensor. For displaying the graph, enter "ACTIVE TEST / A/F CONTROL / USER DATA", select "AFS B1S1 and O2S B1S2" by pressing "YES", "ENTER", then press "F4".

Wiring Diagram:

Step 1-2:

Step 3:

INSPECTION PROCEDURE

HINT:
- If DTC P2238, P2239, P2252 or P2253 is displayed, check the bank 1 sensor 1 circuit.
- Read freeze frame data using the intelligent tester or the OBD II scan tool. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.