Inspection Procedure

WARNING: This page is about a different car, the 2007 Toyota Tacoma. However, it is still accessible from the selected car via links, so may be relevant.

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 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.
Select the following menu items: 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

STANDARD REFERENCE

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.

Fig 1: A/F Sensor (Sensor 1) And HO2 Sensor (Sensor 2) Output Voltage Chart

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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, and press the YES button and then the ENTER button followed by the F4 button.
Following the A/F CONTROL procedure enables technicians to check and graph the voltage outputs of both the A/F and HO2 sensors.

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 an intelligent tester. Freeze frame data record 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.

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

Connect an intelligent tester to the DLC3.
Turn the ignition switch ON.
Turn the tester ON.
Select the following menu items: DIAGNOSIS I ENHANCED OBD II / DTC INFO / CURRENT CODES.

Read 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 DTC CHART

A: Go to Next Step

INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

Disconnect the A4 or A5 A/F sensor connector.

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

Standard Resistance

TESTER CONNECTIONS AND SPECIFIED CONDITIONS

Tester Connections	Specified Conditions
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.

Fig 2: Inspecting Air Fuel Ratio Sensor (Heater Resistance)

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

NG: REPLACE AIR FUEL RATIO SENSOR

OK: Go to Next Step

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

Disconnect the A4 or A5 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 CONNECTIONS AND SPECIFIED CONDITIONS

Tester Connections	Specified Conditions
+B (A4-2) - Body ground	9 to 14 V
+B (A5-2) - Body ground	9 to 14 V

Turn the ignition switch OFF.
Disconnect the E5 ECM connector.

Check the resistance.

Standard Resistance (Check for open)

TESTER CONNECTIONS AND SPECIFIED CONDITIONS

Tester Connections	Specified Conditions
HT (A4-1) - HA1A (ES-2)	Below 1 Ω
AF+ (A4-3) - A1A+ (E5-22)
AF- (A4-4) - A1A- (E5-30)
HT (A5-1) - HA2A (E5-1)
AF+ (A5-3) - A2A+ (E5-23)
AF- (AS-4) - A2A- (E5-31)

Fig 3: Checking Harness And Connector (A/F Sensor - ECM)

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Standard Resistance (Check for short)

TESTER CONNECTIONS AND SPECIFIED CONDITIONS

Tester Connections	Specified Conditions
HT (A4-1) or HA1A (E5-2)- Body ground	10 kΩ or higher
AF+ (A4-3) or A1A+ (E5-22) - Body ground
AF- (A4-4) or A1A- (E5-30) - Body ground
HT (A5-1) or HA2A (E5-1) - Body ground
AF+ (A5-3) or A2A+ (E5-23) - Body ground
AF- (A5-4) or A2A- (E5-31) - Body ground

Reconnect the ECM connector.

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)

Connect an intelligent tester to the DLC3.
Turn the ignition switch ON and turn the tester ON.
Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.

Read DTCs.

Result

RESULT REFERENCE

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
PERFORM CONFIRMATION DRIVING PATTERN

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

Connect an intelligent tester to the DLC3.
Turn the ignition switch ON and turn the tester ON.
Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.

Read DTCs.

Result

RESULT REFERENCE

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

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

A: END