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 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 B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2) 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 in the fuel injection volume.

TYPICAL MALFUNCTION THRESHOLDS

Tester Display (Sensor)	Injection Volume	Status	Voltage
AFS B1 S1 or AFS B2S1 (A/F)	+25%	Rich	Less than 3.0 V
AFS B1 S1 or AFS B2S1 (A/F)	-12.5%	Lean	More than 3.35 V
O2S B1 S2 or O2S B2 S2 (HO2)	+25%	Rich	More than 0.55 V
O2S B1 S2 or O2S B2 S2 (HO2)	-12.5%	Lean	Less than 0.4 V

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: Identifying A/F Sensor Output Voltage & HO2 Sensor Output Voltage Table

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 B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2, and press the YES button and then the ENTER button followed by the F4 button.

HINT:

DTC P2A00 or P2A03 may also 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 the 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 (See FREEZE FRAME DATA ).

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

Connect the intelligent tester to the DLC3.
Turn the engine switch on (IG).
Turn the tester on.
Enter the following menus: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.

Read the DTCs.

Result

RESULT REFERENCE

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 or P2A03 are output, troubleshoot those DTCs first.

B: GO TO DIAGNOSTIC TROUBLE CODE TABLE

A: Go to Next Step

INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

Disconnect the B3 or B4 A/F sensor connector.

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

Standard resistance (Bank 1 sensor 1)

RESISTANCE REFERENCE (BANK 1 SENSOR 1)

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

Standard resistance (Bank 2 sensor 1)

RESISTANCE REFERENCE (BANK 2 SENSOR 1)

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

Fig 2: Identifying B3 & B4 A/F Sensor Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Reconnect the A/F sensor connector.

NG: REPLACE AIR FUEL RATIO SENSOR (See REMOVAL )

OK: Go to Next Step

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

Disconnect the B3 and B4 A/F sensor connectors.
Turn the engine switch on (IG).

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

Standard voltage

VOLTAGE SPECIFICATION TABLE

Tester Connection	Specified Condition
+B (B3-2) - Body ground	9 to 14 V
+B (B4-2) - Body ground	9 to 14 V

Turn the engine switch off.
Disconnect the B12 ECM connector.

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

Standard resistance (Check for open)

RESISTANCE REFERENCE (CHECK FOR OPEN)

Tester Connection	Specified Condition
HT (B3-1) - HA1A (B12-86)	Below 1 Ω
AF+ (B3-3) - A1A+ (B12-93)	Below 1 Ω
AF- (B3-4) - A1 A- (B12-116)	Below 1 Ω
HT (B4-1) - HA2A (B12-109)	Below 1 Ω
AF+ (B4-3) - A2A+ (B12-120)	Below 1 Ω
AF- (B4-4) - A2A- (B12-119)	Below 1 Ω

Standard resistance (Check for short)

RESISTANCE REFERENCE (CHECK FOR SHORT)

Tester Connection	Specified Condition
HT (B3-1) or HA1A (B12-86) - Body ground	10 kΩ or higher
AF+ (B3-3) or A1A+ (B12-93) - Body ground	10 kΩ or higher
AF- (B3-4) or A1A- (B12-116) - Body ground	10 kΩ or higher
HT (B4-1) or HA2A (B12-109) - Body ground	10 kΩ or higher
AF+ (B4-3) or A2A+ (B12-120) - Body ground	10 kΩ or higher
AF- (B4-4) or A2A- (B12-119) - Body ground	10 kΩ or higher

Fig 3: Identifying B3 & B4 A/F Sensor Connectors Terminals

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

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 the DTCs using the intelligent tester.

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

Result

RESULT REFERENCE

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

B: REPLACE ECM (See REMOVAL )

A: Go to Next Step

REPLACE AIR FUEL RATIO SENSOR
1. Replace the air fuel ratio sensor (See REMOVAL ).
PERFORM CONFIRMATION DRIVING PATTERN

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

Read the DTCs using the intelligent tester.

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

Result

RESULT REFERENCE

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

B: REPLACE ECM (See REMOVAL )

A: END