SFI SYSTEM, Diagnostic DTC:P2237, P2238, P2239, P2252, P2253

DTC Code	DTC Name
P2237	Oxygen (A/F) Sensor Pumping Current Circuit / Open (Bank 1 Sensor 1)
P2238	Oxygen (A/F) Sensor Pumping Current Circuit Low (Bank 1 Sensor 1)
P2239	Oxygen (A/F) Sensor Pumping Current Circuit High (Bank 1 Sensor 1)
P2252	Oxygen (A/F) Sensor Reference Ground Circuit Low (Bank 1 Sensor 1)
P2253	Oxygen (A/F) Sensor Reference Ground Circuit High (Bank 1 Sensor 1)

DESCRIPTION

Tech Tips

Although the DTC titles say oxygen sensor, these DTCs relate to the air fuel ratio sensor.
Sensor 1 refers to the sensor mounted in front of the three-way catalytic converter and located near the engine assembly.

These DTCs are set when there is an open or short in the air fuel ratio sensor circuit, or if air fuel ratio sensor output drops. To detect these problems, the voltage of the air fuel ratio sensor is monitored when the ignition switch is turned ON, and the admittance (admittance is an electrical term that indicates the ease of flow of current) is checked while driving. If the voltage of the air fuel ratio sensor is between 0.6 V and 4.5 V, it is considered normal. If the voltage is out of the specified range, or the admittance is less than the standard value, the ECM will determine that there is a malfunction in the air fuel ratio sensor. If the same malfunction is detected in next driving cycle, the MIL will be illuminated and a DTC will be stored.

The air fuel ratio sensor, which is located between the exhaust manifold and catalyst, consists of alloyed metal elements and a heater.

Depending on the engine operating conditions, the heater heats the sensor elements to activate them. Battery voltage is applied to the heater, and the sensor ground is controlled by the ECM using a duty ratio.

The sensor elements convert the oxygen concentration in the exhaust gas into voltage values to output. Based on the voltage, the ECM determines the air fuel ratio and regulates the fuel injection volume depending on the air fuel ratio and engine operating conditions. The voltage changes between 0.6 V and 4.5 V while the engine is running. If the air fuel ratio is lean, which means the oxygen concentration in the exhaust gas is high, the voltage is high. If the air fuel ratio is rich, which means the oxygen concentration in the exhaust gas is low, the voltage is low.

DTC No.	DTC Detection Condition	Trouble Area
P2237	Open in circuit between terminals A1A+ and A1A- of air fuel ratio sensor while engine running (2-trip detection logic)	Open or short in air fuel ratio sensor (sensor 1) circuit Air fuel ratio sensor (sensor 1) ECM
P2238	Any of following conditions met (2-trip detection logic): Air fuel ratio sensor output drops while engine running Voltage at terminal A1A+ 0.5 V or less Voltage difference between terminals A1A+ and A1A- 0.1 V or less Voltage difference between terminals A1A+ and A1A- 0.8 V or high	Open or short in air fuel ratio sensor (sensor 1) circuit Air fuel ratio sensor (sensor 1) EGR valve assembly ECM
P2239	A1A+ voltage more than 4.5 V (2-trip detection logic)	Open or short in air fuel ratio sensor (sensor 1) circuit Air fuel ratio sensor (sensor 1) ECM
P2252	A1A- voltage 0.5 V or less (2-trip detection logic)	Open or short in air fuel ratio sensor (sensor 1) circuit Air fuel ratio sensor (sensor 1) ECM
P2253	A1A- voltage more than 4.5 V (2-trip detection logic)	Open or short in air fuel ratio sensor (sensor 1) circuit Air fuel ratio sensor (sensor 1) ECM

WIRING DIAGRAM

INSPECTION PROCEDURE

Note

Inspect the fuses for circuits related to this system before performing the following inspection procedure.

Tech Tips

Intelligent tester only:

Malfunctioning areas can be identified by performing the Control the Injection Volume for A/F Sensor function provided in the Active Test. The Control the Injection Volume for A/F Sensor function can help to determine whether the Air Fuel Ratio (A/F) sensor, Heated Oxygen (HO2) sensor and other potential trouble areas are malfunctioning.

The following instructions describe how to conduct the Control the Injection Volume for A/F Sensor operation using the intelligent tester.

Connect the intelligent tester to the DLC3.
Start the engine and turn the tester on.
Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.
Perform the Active Test operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume.)
Monitor the output voltages of the A/F and HO2 sensors (AFS Voltage B1S1 and O2S B1S2) displayed on the tester.

Tech Tips

The Control the Injection Volume for A/F Sensor operation lowers the fuel injection volume by 12.5% or increases the injection volume by 25%.
Each sensor reacts in accordance with increases and decreases in the fuel injection volume.

Tester Display (Sensor)	Injection Volume	Status	Voltage
AFS Voltage B1S1 (A/F)	+25%	Rich	Less than 3.1 V
AFS Voltage B1S1 (A/F)	-12.5%	Lean	More than 3.4 V
O2S B1S2 (HO2)	+25%	Rich	More than 0.55 V
O2S B1S2 (HO2)	-12.5%	Lean	Less than 0.4 V

Note

The air fuel ratio sensor has an output delay of a few seconds and the heated oxygen sensor has a maximum output delay of approximately 20 seconds.

Case	A/F Sensor (Sensor 1) Output Voltage	HO2 Sensor (Sensor 2) Output Voltage	Main Suspected Trouble Area
1			-
2			A/F sensor A/F sensor heater A/F sensor circuit
3			HO2 sensor HO2 sensor heater HO2 sensor circuit
4			Injector Fuel pressure Gas leak from exhaust system (Air-fuel ratio extremely rich or lean)

Following the Control the Injection Volume for A/F Sensor procedure enables technicians to check and graph the voltage outputs of both the A/F and HO2 sensors.
To display the graph, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / A/F Control System / AFS Voltage B1S1 and O2S B1S2.

Tech Tips

Read freeze frame data using an intelligent tester. 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 moving or stationary, 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.

PROCEDURE

CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO P2237, P2238, P2239, P2252 OR P2253)

Connect the intelligent tester to the DLC3.
Turn the ignition switch to ON.
Turn the tester on.
Enter the following menus: Powertrain / Engine and ECT / DTC.

Read the DTC.

Result
Result	Proceed to
P2237, P2238, P2239, P2252 or P2253	A
P2237, P2238, P2239, P2252 or P2253 and other DTCs	B

GO TO DTC CHART Click here

PERFORM ACTIVE TEST USING INTELLIGENT TESTER (OPERATE EGR VALVE)

Connect the intelligent tester to the DLC3.
Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher.

Tech Tips

The A/C switch and all accessory switches should be off.
Turn the tester on.
Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the EGR Step Position.

Check the MAP in Data List and the idling condition while performing Active Test.

OK
MAP and idling condition change in response to EGR step position.

Standard

EGR Step Position (Active Test)

0 Steps

0 to 30 Steps

30 to 40 Steps or Higher

Idling condition

Steady idling

Engine changes from steady to rough idling

Engine changes from rough idling to engine stall

MAP value

(Data List)

28 to 48 kPa

(EGR valve is fully closed)

MAP value is at least +10 to 15 kPa higher than when EGR valve is fully closed

80 to 110 kPa

(After engine stall)

Tech Tips

During Active Test, if the idling condition does not change in response to EGR step position, then there is probably a malfunction in EGR valve.

Result
Result	Proceed to
Outside standard range	A
Within standard range	B

CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM) Click here

CHECK WHETHER DTC OUTPUT RECURS (DTC P0401)

Connect the intelligent tester to the DLC3.
Turn the ignition switch to ON.
Turn the tester on.
Clear the DTC.
Turn the ignition switch off and wait for 30 seconds.
Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher.

Tech Tips

The A/C switch and all accessory switches should be off.
Switch the ECM from normal mode to check mode.
Drive the vehicle at 60 km/h (37 mph) with the shift lever in B.
CAUTION:
- Strictly observe speed limits and traffic laws when performing the confirmation drive pattern.
Perform fuel-cut operation for 5 seconds or more, with the accelerator pedal fully released.
Tech Tips
- If the deceleration was not completed, perform the confirmation driving pattern again.
Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.
Input the DTCs to be confirmed.

Check the DTC judgment result.

Result
Result	Proceed to
No output	A
P0401	B

Intelligent Tester
Tester Display	Description
NORMAL	DTC judgment completed System normal
ABNORMAL	DTC judgment completed System abnormal
INCOMPLETE	DTC judgment not completed You should perform driving pattern after confirming DTC enabling conditions
UNKNOWN	Unable to perform DTC judgment Number of DTCs which do not fulfill DTC preconditions has reached ECU's memory limit

Tech Tips

If the DTC judgment result is INCOMPLETE or UNKNOWN, drive the vehicle again at 60 km/h (37 mph) with the shift lever in B, perform fuel-cut operation for 5 seconds or more with the accelerator pedal fully released, and check the DTC judgment result.

GO TO DTC CHART Click here

CHECK HARNESS AND CONNECTOR (AIR FUEL RATIO SENSOR - ECM)

Text in Illustration
*1	Front view of wire harness connector: (to Air Fuel Ratio Sensor)
*2	Front view of wire harness connector: (to ECM)

Disconnect the air fuel ratio sensor connector.

Disconnect the ECM connector.

Measure the resistance according to the value(s) in the table below.

Standard Resistance (Check for Open)

Tester Connection	Condition	Specified Condition
B34-3 (A1A+) - B8-103 (A1A+)	Always	Below 1 Ω
B34-4 (A1A-) - B8-126 (A1A-)	Always	Below 1 Ω

Standard Resistance (Check for Short)

Tester Connection	Condition	Specified Condition
B34-3 (A1A+) or B8-103 (A1A+) - Body ground	Always	10 kΩ or higher
B34-4 (A1A-) or B8-126 (A1A-) - Body ground	Always	10 kΩ or higher

Reconnect the ECM connector.
Reconnect the air fuel ratio sensor connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR

REPLACE AIR FUEL RATIO SENSOR
1. Replace the air fuel ratio sensor Click here.
NEXT
PERFORM CONFIRMATION DRIVING PATTERN
1. Connect an intelligent tester to the DLC3.
2. Turn the ignition switch to ON.
3. Turn the tester on.
4. Switch the ECM from normal mode to check mode Click here.
5. Drive the vehicle referring to the Confirmation Driving Pattern Click here.
NEXT

CHECK WHETHER DTC OUTPUT RECURS (DTC P2237, P2238, P2239, P2252 OR P2253)

Connect an intelligent tester to the DLC3.
Turn the ignition switch to ON.
Turn the tester on.
Enter the following menus: Powertrain / Engine and ECT / DTC.

Read DTCs (Pending DTCs).

Result
Result	Proceed to
No output	A
P2237, P2238, P2239, P2252 or P2253	B

REPLACE ECM Click here

END