Inspection Procedure

HINT:

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 an 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.
Select the following menu items on the tester: 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 voltage outputs of the A/F and HO2 sensors (AFS B1S1 and O2S B1S2 or AFS B2S1 and 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

FUEL INJECTION VOLUME CHART

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

SENSOR OUTPUT VOLTAGE SPECIFICATION

Case	A/F Sensor (Sensor 1) Output Voltage	HO2 Sensor (Sensor 2) Output Voltage	Main Suspected Trouble Area
1	Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.	Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.	-
2	Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.	Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.	A/F sensor A/F sensor heater A/F sensor circuit
3	Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.	Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.	HO2 sensor HO2 sensor heater HO2 sensor circuit
4	Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.	Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.	Fuel pressure Gas leakage from exhaust system (Air-fuel ratio extremely lean or rich)

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, select the following menu items on the tester: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL / USER DATA / AFS B1S1 and O2S B1S2 or AFS B2S1 and O2S B2S2. Press the YES button and then the ENTER button. Then press the F4 button.
HINT:
- DTC P2A00 or P2A03 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. 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.

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

Connect the intelligent tester to the DLC3.
Turn the ignition switch on (IG).
Turn the tester on.
Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.
Read the 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 or P2A03 are output, troubleshoot those DTCs first.

B: GO TO DTC CHART (See DIAGNOSTIC TROUBLE CODE CHART )

A: Go to Next Step

INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

Disconnect the A/F sensor connectors.

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

Standard resistance:

Bank 1

TESTER CONNECTION SPECIFIED CONDITION

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

Bank 2

TESTER CONNECTION SPECIFIED CONDITION

Tester Connection	Condition	Specified Condition
HA2A (1) - +B (2)	20°C (68°F)	1.8 to 3.4 Ω
HA2A (1) - A2A- (4)	Always	10 kΩ or higher

Reconnect the A/F sensor connector.

Fig 1: Identifying A/F Sensor Connector Terminals

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

NG: REPLACE AIR FUEL RATIO SENSOR (See REMOVAL )

OK: Go to Next Step

INSPECT ENGINE ROOM JUNCTION BLOCK ASSEMBLY (A/F SENSOR RELAY)

Remove the engine room junction block.

Measure the A/F sensor relay resistance.

Standard resistance

TESTER CONNECTION SPECIFIED CONDITION

Tester Connections	Specified Conditions
1F-1 - 1C-6	10 kΩ or higher
1F-1 - 1C-6	Below 1 Ω (when battery voltage applied to terminals 1D-5 and 1H-2)

Reinstall the engine room junction block.

Fig 2: Identifying Engine Room Junction Block Assembly Connector Terminals

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

NG: REPLACE ENGINE ROOM JUNCTION BLOCK ASSEMBLY

OK: Go to Next Step

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

Disconnect the A/F sensor connectors.
Turn the ignition switch on (IG).

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

Standard voltage

TESTER CONNECTION SPECIFIED CONDITION

Tester Connection	Specified Condition
+B (B32-2) - Body ground	9 to 14 V
+B (B26-2) - Body ground	9 to 14 V

Turn the ignition switch off.
Disconnect the ECM connector.

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

Standard resistance:

Check for open

TESTER CONNECTION SPECIFIED CONDITION

Tester Connection	Specified Condition
HA1A (B32-1) - HA1A (B46-2)	Below 1 Ω
A1A+ (B32-3) - A1A+ (B46-22)	Below 1 Ω
A1A- (B32-4) - A1A- (B46-30)	Below 1 Ω
HA2A (B26-1) - HA2A (B46-1)	Below 1 Ω
A2A+ (B26-3) - A2A+ (B46-23)	Below 1 Ω
A2A- (B26-4) - A2A- (B46-31)	Below 1 Ω

Check for short

TESTER CONNECTION SPECIFIED CONDITION

Tester Connection	Specified Condition
HA1A (B32-1) or HA1A (B46-2) - Body ground	10 kΩ or higher
A1A (B32-3) or A1A+ (B46-22) - Body ground	10 kΩ or higher
A1A- (B32-4) or A1A- (B46-30) - Body ground	10 kΩ or higher
HA2A (B26-1) or HA2A (B46-1) - Body ground	10 kΩ or higher
A2A+ (B26-3) or A2A+ (B46-23) - Body ground	10 kΩ or higher
A2A- (B26-4) or A2A- (B46-31) - Body ground	10 kΩ or higher

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

Fig 3: Identifying A/F Sensor And ECM Connector Terminals

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

Fig 4: Oxygen (A/F) Sensor Heater Control System Diagram (Bank 1 Sensor 1)

Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

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.
Select the following menu items: 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 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.
Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / PENDING CODES.
Result

RESULT CHART

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

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

A: END