SFI SYSTEM(w/o Secondary Air Injection System), Diagnostic DTC:P2237, P2238, P2239, P2240, P2241, P2242, P2252, P2253, P2255, P2256

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)
P2240	Oxygen (A/F) Sensor Pumping Current Circuit / Open (Bank 2 Sensor 1)
P2241	Oxygen (A/F) Sensor Pumping Current Circuit Low (Bank 2 Sensor 1)
P2242	Oxygen (A/F) Sensor Pumping Current Circuit High (Bank 2 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)
P2255	Oxygen (A/F) Sensor Reference Ground Circuit Low (Bank 2 Sensor 1)
P2256	Oxygen (A/F) Sensor Reference Ground Circuit High (Bank 2 Sensor 1)

DESCRIPTION

Refer to DTC P0031 Click here.

DTC Code	DTC Detection Condition	Trouble Area
P2237 P2240	An open in the circuit between terminals A1A+ and A1A-/A2A+ and A2A- of the A/F sensor while the engine is running (2 trip detection logic).	Open in Air Fuel ratio (A/F) sensor (for Bank 1, 2 Sensor 1) circuit Air Fuel ratio (A/F) sensor (for Bank 1, 2 Sensor 1) ECM
P2238 P2241	Case 1: Condition (a) or (b) continues for 5.0 seconds or more (1 trip detection logic): (a) The A1A+/A2A+ voltage is 0.5 V or less. (b) (A1A+/A2A+) - (A1A-/A2A-) = 0.1 V or less. Case 2: The A/F sensor admittance is below 0.022 1/Ω (2 trip detection logic).	Open or short in A/F sensor (for Bank 1, 2 Sensor 1) circuit A/F sensor (for Bank 1, 2 Sensor 1) ECM
P2239 P2242	The A1A+/A2A+ voltage is higher than 4.5 V for 5.0 seconds or more (2 trip detection logic).	Open or short in A/F sensor (for Bank 1, 2 Sensor 1) circuit A/F sensor (for Bank 1, 2 Sensor 1) ECM
P2252 P2255	The A1A-/A2A- voltage is 0.5 V or less for 5.0 seconds or more (2 trip detection logic).	Open or short in A/F sensor (for Bank 1, 2 Sensor 1) circuit A/F sensor (for Bank 1, 2 Sensor 1) ECM
P2253 P2256	The A1A-/A2A- voltage is higher than 4.5 V for 5.0 seconds or more (2 trip detection logic).	Open or short in A/F sensor (for Bank 1, 2 Sensor 1) circuit A/F sensor (for Bank 1, 2 Sensor 1) ECM

Tech Tips

DTCs P2237, P2238, P2239, P2252 and P2253 indicate malfunctions related to the bank 1 A/F sensor circuit.
DTCs P2240, P2241, P2242, P2255 and P2256 indicate malfunctions related to the bank 2 A/F sensor circuit.

MONITOR DESCRIPTION

These DTCs are stored when there is an open or short in the A/F sensor circuit, or if A/F sensor output drops.

To detect these problems, the voltage of the A/F sensor is monitored when turning the engine switch on (IG), 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 A/F sensor is between 0.6 V and 4.5 V, it is considered normal. If the voltage is outside of the specified range, or the admittance is less than the standard value, the ECM will determine that there is a malfunction in the A/F sensor. If the same malfunction is detected in the next driving cycle, the MIL is illuminated and a DTC is stored.

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

WIRING DIAGRAM

Refer to DTC P0031 Click here.

CAUTION / NOTICE / HINT

Tech Tips

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.

(a) Connect the tester to the DLC3.
(b) Start the engine and turn the tester on.
(c) Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
(d) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F sensor.
(e) Perform the Active Test operation with the engine idling (press the RIGHT or LEFT button to change the fuel injection volume).
(f) Monitor the output voltages of the A/F and HO2 sensors (AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2) 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.

Standard

Display Item (Sensor)	Injection Volume	Status	Voltage
AFS B1 S1 (A/F)	+25%	Rich	Below 3.0
AFS B1 S1 (A/F)	-12.5%	Lean	Higher than 3.35
O2S B1 S2 (HO2)	+25%	Rich	Higher than 0.55
O2S B1 S2 (HO2)	-12.5%	Lean	Below 0.4
AFS B2 S1 (A/F)	+25%	Rich	Below 3.0
AFS B2 S1 (A/F)	-12.5%	Lean	Higher than 3.35
O2S B2 S2 (HO2)	+25%	Rich	Higher than 0.55
O2S B2 S2 (HO2)	-12.5%	Lean	Below 0.4

Note

The A/F sensor has an output delay of a few seconds and the HO2 sensor has a maximum output delay of approximately 20 seconds.

Following the Control the Injection Volume for A/F Sensor procedure enables technicians to check and graph the output voltages 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 or AFS Voltage B2S1 and O2S B2S2.

Tech Tips

Read freeze frame data using the intelligent tester. Freeze frame data records the engine condition when malfunctions are detected. 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.
Bank 1 refers to the bank that includes the No. 1 cylinder*.

*: The No. 1 cylinder is the cylinder which is farthest from the transmission.
Bank 2 refers to the bank that does not include the No. 1 cylinder.
Sensor 1 refers to the sensor closest to the engine assembly.
Sensor 2 refers to the sensor farthest away from the engine assembly.

PROCEDURE

CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM)

Disconnect the C22 or C23 Air Fuel ratio (A/F) sensor connector.

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

Standard Voltage
Tester Connection	Switch Condition	Specified Condition
C22-2 (+B) - Body ground	Engine switch on (IG)	11 to 14 V
C23-2 (+B) - Body ground	Engine switch on (IG)	11 to 14 V

Turn the engine switch off.
Disconnect the C45 ECM connector.

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

Standard Resistance
Tester Connection	Condition	Specified Condition
C22-1 (HA1A) - C45-22 (HA1A)	Always	Below 1 Ω
C22-3 (A1A+) - C45-126 (A1A+)	Always	Below 1 Ω
C22-4 (A1A-) - C45-125 (A1A-)	Always	Below 1 Ω
C23-1 (HA2A) - C45-20 (HA2A)	Always	Below 1 Ω
C23-3 (A2A+) - C45-103 (A2A+)	Always	Below 1 Ω
C23-4 (A2A-) - C45-102 (A2A-)	Always	Below 1 Ω
C22-1 (HA1A) or C45-22 (HA1A) - Body ground	Always	10 kΩ or higher
C22-3 (A1A+) or C45- 126 (A1A+) - Body ground	Always	10 kΩ or higher
C22-4 (A1A-) or C45-125 (A1A-) - Body ground	Always	10 kΩ or higher
C23-1 (HA2A) or C45-20 (HA2A) - Body ground	Always	10 kΩ or higher
C23-3 (A2A+) or C45- 103 (A2A+) - Body ground	Always	10 kΩ or higher
C23-4 (A2A-) or C45-102 (A2A-) - Body ground	Always	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

REPLACE AIR FUEL RATIO SENSOR
1. Replace the air fuel ratio sensor Click here.
NEXT

CHECK WHETHER DTC OUTPUT RECURS

Connect the intelligent tester to the DLC3.
Turn the engine switch on (IG) and turn the tester on.
Clear DTCs Click here.
Start the engine.
Allow the engine to idle for 5 minutes or more.
Enter the following menus: Powertrain / Engine and ECT / DTC / Pending.

Read pending DTCs.

Result
Result	Proceed to
No DTC is output	A
P2237, P2238, P2239, P2240, P2241, P2242, P2252, P2253, P2255 or P2256 is output	B

END

REPLACE ECM Click here