Inspection Procedure

HINT:

Intelligent tester only:

Malfunctioning areas can be identified by performing the A/F CONTROL function provided in the ACTIVE TEST. The A/F CONTROL 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 A/F CONTROL operation using the intelligent tester.

Connect the intelligent tester to the CAN VIM. Then connect the CAN VIM 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 intelligent tester, enter the following menus: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST /A/F CONTROL.
Perform the A/F CONTROL 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 B1S1 (AFS B2S1) and O2S B1S2 (O2S B2S2)) displayed on the tester.

HINT:

The A/F CONTROL 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:

VOLTAGE SPECIFICATION CHART

Tester Display (Sensor)	Injection Volume	Status	Voltage
AFS B1S1 (AFS B2S1) (A/F)	+25 %	Rich	Less than 3.0
AFS B1S1 (AFS B2S1) (A/F)	-12.5 %	Lean	More than 3.35
O2S B1S2 (O2S B2S2) (HO2)	+25 %	Rich	More than 0.55
O2S B1S2 (O2S B2S2) (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.

Fig 1: Air Fuel Ratio (A/F) Sensor Blinking Pattern

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Following the A/F CONTROL 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: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL / USER DATA / AFS B1S1 and O2S B1S2 or AFS B2S1 and O2S B2S2. Then press the YES button and ENTER button, followed by the F4 button.

HINT:

DTC P2A00 may be also 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 the intelligent tester. Freeze frame data records the engine conditions when malfunctions are detected. 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.

CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P2A00 AND/OR P2A03)

Connect the intelligent tester to the CAN VIM. Then connect the CAN VIM to the DLC3.
Turn the ignition switch ON and turn the tester ON.
Enter the following menus: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.

Read DTCs.

Result

RESULT CHART

Display (DTC Output)	Proceed to
P2A00 and/or P2A03	A
P2A00 and/or P2A03 and other DTCs	B

HINT:

If any DTCs other than P2A00 and/or P2A03 are output, troubleshoot those DTCs first.

B: GO TO DTC CHART

A: GO TO next step

INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

Disconnect the A38 or A39 Air Fuel Ratio (A/F) sensor connector.

Measure the resistance of the A/F sensor connector.

Standard resistance

TESTER CONNECTION SPECIFIED CONDITION CHART

Tester Connection	Specified Condition
HT (1) - +B (2)	1.8 to 3.4 Ω at 20°C (68°F)
HT (1) - AF- (4)	10 kΩ or higher

Reconnect the A/F sensor connector.

NG: REPLACE AIR FUEL RATIO SENSOR

Fig 2: Identifying Air Fuel Ratio (A/F) Sensor Connector

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

OK: GO TO next step

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

Disconnect the A38 or A39 A/F sensor connector.
Turn the ignition switch ON.

Measure the voltage between the +B terminal of the A/F sensor connector and body ground.

Standard voltage

TESTER CONNECTION SPECIFIED CONDITION CHART

Tester Connection	Specified Condition
+B (2) - Body ground	10 V or more

Turn the ignition switch OFF.
Disconnect the E7 ECM connector.

Measure the resistance.

Standard resistance (Check for open)

TESTER CONNECTION SPECIFIED CONDITION CHART

Tester Connection	Specified Condition
HT (A38-1) - HA1A (E7-2)	Below 1 Ω
HT (A39-1) - HA2A (E7-1)
AF+ (A38-3) - A1A+ (E7-22)
AF+ (A39-3) - A2A+ (E7-23)
AF- (A38-4) - A1A- (E7-30)
AF- (A39-4) - A2A- (E7-31)

Standard resistance (Check for short)

TESTER CONNECTION SPECIFIED CONDITION CHART

Tester Connection	Specified Condition
HT (A38-1) or HA1A (E7-2) - Body ground	10 kΩ or higher
HT (A39-1) or HA2A (E7-1) - Body ground
AF+ (A38-3) or A1A+ (E7-22) - Body ground
AF+ (A39-3) or A2A+ (E7-23) - Body ground
AF- (A38-4) or A1 A- (E7-30) - Body ground
AF- (A39-4) or A2A- (E7-31) - Body ground

Fig 3: Identifying A38 And A39 (A/F) Sensor Connector With ECM Connector

Fig 4: Reference (Bank 1 Sensor 1 System Diagram)

NG: REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: GO TO next step

PERFORM CONFIRMATION DRIVING PATTERN

CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00 AND/OR P2A03)

Read DTCs using the intelligent tester.

Enter the following menus: DIAGNOSIS / ENHANCED OBD II / DTC INFO / PENDING CODES.

Result

RESULT CHART

Display (DTC Output)	Proceed to
P2A00 and/or P2A03	A
No output	B

B: CHECK FOR INTERMITTENT PROBLEMS

A: GO TO next step

REPLACE AIR FUEL RATIO SENSOR
1. Replace A/F sensor (see AIR FUEL RATIO SENSOR ).
PERFORM CONFIRMATION DRIVING PATTERN

CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00 AND/OR P2A03)

Read DTCs using the intelligent tester.

Enter the following menus: DIAGNOSIS / ENHANCED OBD II / DTC INFO / PENDING CODES.

Result

RESULT CHART

Display (DTC Output)	Proceed to
P2A00 and/or P2A03	A
No output	B

A: CHECK EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO (REFER TO DTC P0171 PROCEDURE )

B: END