P2238, P2239, P2252, P2253

DTC Code	DTC Name
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

Refer to DTC P2195 Click here.

DTC No.	DTC Detecting Condition	Trouble Area
P2238	A/F sensor circuit low	Open in A/F sensor circuit
	Condition (a) continues for 5.0 sec. or more: AF+ less than 0.5 V	Open or short in A/F sensor circuit A/F sensor A/F sensor heater Integration relay (A/F HEATER RELAY) A/F sensor heater and relay circuit ECM
	Condition (a) continues for 5.0 sec. or more: (AF+) - (AF-) less than 0.1 V
P2239	A/F sensor circuit high	Short in A/F sensor circuit
	Condition (a) continues for 5.0 sec. or more: AF+ greater than 4.5 V	Open or short in A/F sensor circuit A/F sensor A/F sensor heater Integration relay (A/F HEATER RELAY) A/F sensor heater and relay circuit ECM
	Condition (a) continues for 5.0 sec. or more: (AF+) - (AF-) greater than 0.8 V
P2252	Condition (a) continues for 5.0 sec. or more: AF- less than 0.5 V	Open or short in A/F sensor circuit A/F sensor A/F sensor heater Integration relay (A/F HEATER RELAY) A/F sensor heater and relay circuit ECM
P2253	Condition (a) continues for 5.0 sec. or more: AF- greater than 4.5 V

WIRING DIAGRAM

Refer to DTC P2195 Click here.

INSPECTION PROCEDURE

Tech Tips

Malfunctioning areas can be identified by performing the Control the Injection Volume for A/F Sensor operation provided in the Active Test. The Control the Injection Volume for A/F Sensor function can help 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 an intelligent tester.

Connect an intelligent tester to the DLC3.
Start the engine and turn the tester ON.
Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
On the tester, select the following menu items: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.
Perform the Control the Injection Volume for A/F Sensor operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).
Monitor the voltage outputs 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.

Voltage

Tester Display (Sensor)	Injection Volumes	Status	Voltages
AFS Voltage B1S1 (A/F)	+25 %	Rich	Less than 3.1
AFS Voltage B1S1 (A/F)	-12.5 %	Lean	More than 3.4
O2S B1S2 (HO2)	+25 %	Rich	More than 0.5
O2S B1S2 (HO2)	-12.5 %	Lean	Less than 0.4

Note

The Air-Fuel Ratio (A/F) sensor has an output delay of a few seconds and the Heated Oxygen (HO2) sensor has a maximum output delay of approximately 20 seconds.

Case	A/F Sensor (Sensor 1) Output Voltage	HO2 Sensor (Sensor 2) Output Voltage	Mainly Suspected Trouble Areas
1	Injection volume +25 % -12.5 %	Injection volume +25 % -12.5 %	-
1	Output voltage More than 3.4 V Less than 3.1 V	Output voltage More than 0.5 V Less than 0.4 V	-
2	Injection volume +25 % -12.5 %	Injection volume +25 % -12.5 %	A/F sensor A/F sensor heater A/F sensor circuit
2	Output voltage Almost no reaction	Output voltage More than 0.5 V Less than 0.4 V	A/F sensor A/F sensor heater A/F sensor circuit
3	Injection volume +25 % -12.5 %	Injection volume +25 % -12.5 %	HO2 sensor HO2 sensor heater HO2 sensor circuit
3	Output voltage More than 3.4 V Less than 3.1 V	Output voltage Almost no reaction	HO2 sensor HO2 sensor heater HO2 sensor circuit
4	Injection volume +25 % -12.5 %	Injection volume +25 % -12.5 %	Injector Fuel pressure Gas leakage from exhaust system (Air-fuel ratio extremely lean or rich)
4	Output voltage Almost no reaction	Output voltage Almost no reaction

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, select the following menu items on the tester: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / User Data / AFS Voltage B1S1 and O2S B1S2.

Tech Tips

DTC P2A00 may be set when the air-fuel ratio is stuck rich or lean.
A low A/F sensor voltage could be caused by a rich air-fuel mixture. Check for conditions that would cause the engine to run rich.
A high A/F sensor voltage could be caused by a lean air-fuel mixture. Check for conditions that would cause the engine to run lean.
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 be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air-fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.

PROCEDURE

INSPECT AIR FUEL RATIO SENSOR (RESISTANCE OF A/F SENSOR HEATER)

Disconnect the D33 Air-Fuel Ratio (A/F) sensor connector.

Measure the resistance between the terminals of the A/F sensor connector.

Resistance

Tester Connections	Specified Conditions
HA1A (1) - +B (2)	1.8 Ω to 3.4 Ω at 20°C (68°F)
HA1A (1) - A1A- (4)	10 kΩ or higher

Reconnect the A/F sensor connector.

NG

REPLACE AIR FUEL RATIO SENSOR

OK

INSPECT INTEGRATION NO.1 RELAY (A/F HEATER RELAY)

Remove the integration relay from the engine room R/B No.1.

Check the integration relay (A/F HEATER relay).

Resistance

Tester Connections

Specified Conditions

A1 - C4

10 kΩ or higher

A1 - C4

Below 1 Ω

(when battery voltage applied to terminals C2 and C3)

Reinstall the integration relay.

NG

REPLACE INTEGRATION NO.1 RELAY

OK

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

Check the harness and connectors between the ECM and A/F sensor.

Disconnect the D33 A/F sensor connector.
Disconnect the D1 ECM connector.

Measure the resistance.

Resistance (Check for open)

Tester Connections	Specified Conditions
HA1A (D33-1) - HA1A (D1-1)	Below 1 Ω

Resistance (Check for short)

Tester Connections	Specified Conditions
HA1A (D33-1) or HA1A (D1-1) - Body ground	10 kΩ or higher

Reconnect the A/F sensor connector.
Reconnect the ECM connector.

Check the harness and connector between the A/F sensor and integration relay.

Disconnect the D33 A/F sensor connector.
Disconnect the integration relay connector.

Measure the resistance.

Resistance (Check for open)

Tester Connections	Specified Conditions
+B (D33-2) - Integration relay (C4)	Below 1 Ω

Resistance (Check for short)

Tester Connections	Specified Conditions
+B (D33-2) or Integration relay (C4) - Body ground	10 kΩ or higher

Reconnect the A/F sensor connect.
Reconnect the integration relay connector.

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

REPLACE ECM

SFI SYSTEM (w/ Secondary Air Injection System), Diagnostic DTC:P2238, P2239, P2252, P2253