Inspection Procedure

HINT:

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

Connect the Techstream to the DLC3.
Start the engine and turn the Techstream on.
Warm up the engine at an engine speed of 2, 500 rpm for approximately 90 seconds.
Enter the following menus: 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 output voltages of the A/F and HO2 sensors (AFS B1S1 and O2S B1S2 or AFS B2S1 and O2S B2S2) displayed on the Techstream.

HINT:

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 in the fuel injection volume.

Standard:

VOLTAGE STATUS CHART

Techstream Display (Sensor)	Injection Volume	Status	Voltage
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.

MAIN SUSPECTED TROUBLE AREA

Case	Air Fuel Ratio Sensor (Sensor 1) Output Voltage	Heated Oxygen Sensor (Sensor 2) Output Voltage	Main Suspected Trouble Area
1	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	-
2	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	A/F sensor A/F sensor heater A/F sensor circuit
3	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	HO2 sensor HO2 sensor heater HO2 sensor circuit
4	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Injector Fuel pressure Gas leak from exhaust system (Air fuel ratio extremely rich or lean)

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, enter the following menus: Powertrain/Engine and ECT/Active Test/Control the Injection Volume for A/F Sensor/A/F Control System/AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2 then press the graph button on the Data List view.

HINT:

DTC P2A00 may be also set when the air-fuel ratio is stuck at 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 Techstream. 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)

Connect the Techstream to the DLC3.
Turn the ignition switch to the ON position.
Turn the Techstream on.
Enter the following menus: Powertrain/Engine and ECT/Trouble Codes.

Read the DTCs.

Result

RESULT CHART

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

HINT:

If any DTCs other than P2A00 are output, troubleshoot those DTCs first.

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

A: Go to Next Step

READ VALUE USING TECHSTREAM (OUTPUT VOLTAGE OF A/F SENSOR)

Connect the Techstream to the DLC3.
Start the engine.
Turn the Techstream on.
Warm up the Air-Fuel Ratio (A/F) sensor at an engine speed of 2, 500 rpm for 90 seconds.
Enter the following menus: Powertrain/Engine and ECT/Data List/A/F Control System/AFS B1 S1 and Engine Speed: then press the Record button.

Check the A/F sensor voltage 3 times, when the engine is in each of the following conditions:

While idling (check for at least 30 seconds)
At an engine speed of approximately 2, 500 rpm (without any sudden changes in engine speed)
The engine speed is raised to 4, 000 rpm and then the accelerator pedal is quickly released so that the throttle valve is fully closed.

Standard voltage

A/F SENSOR VOLTAGE VARIATION CHART

Condition	A/F Sensor Voltage Variation	Reference
(1) and (2)	Changes at approximately 3.3 V	Between 3.1 V and 3.5 V
(3)	Increases to 3.8 V or more	This occurs during engine deceleration (when fuel-cut performed)

For more information, see the diagrams below.

Fig 1: Engine RPM And A/F Sensor Voltage Malfunction Chart

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

HINT:

If the output voltage of the A/F sensor remains at approximately 3.3 V (see Malfunction Condition diagram) under any conditions, including those above, the A/F sensor may have an open circuit. (This will also happen if the A/F sensor heater has an open circuit.)
If the output voltage of the A/F sensor remains at either approximately 3.8 V or more, or 2.8 V or less (see Malfunction Condition diagram) under any conditions, including those above, the A/F sensor may have a short circuit.
The ECM stops fuel injection (fuel cut) during engine deceleration. This causes a lean condition and results in a momentary increase in the A/F sensor output voltage.
The ECM must establish a closed throttle valve position learning value to perform fuel cut. If the battery terminal has been reconnected, the vehicle must be driven at over 10 mph (16 km/h) to allow the ECM to learn the closed throttle valve position.
When the vehicle is driven: The output voltage of the A/F sensor may be below 2.8 V during fuel enrichment. For the vehicle, this is translated to a sudden increase in speed with the accelerator pedal fully depressed when trying to overtake another vehicle. The A/F sensor is functioning normally.
The A/F sensor is a current output element; therefore, the current is converted into a voltage inside the ECM. Measuring the voltage at the connectors of the A/F sensor or ECM will show a constant voltage result.

NG: Go to step 9

OK: Go to Next Step

PERFORM CONFIRMATION DRIVING PATTERN

CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00)

Read the DTCs using the Techstream.

Enter the following menus: Powertrain/Engine and ECT/Trouble Codes.

Result

RESULT CHART

Display (DTC Output)	Proceed to
P2A00	A
No output	B

B: Go to step 8

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)

Read the DTCs using the Techstream.

Enter the following menus: Powertrain/Engine and ECT/Trouble Codes.

Result

RESULT CHART

Display (DTC Output)	Proceed to
No output	A
P2A00	B

B: REPLACE ECM AND PERFORM CONFIRMATION DRIVING PATTERN

A: Go to Next Step

CONFIRM WHETHER VEHICLE HAS RUN OUT OF FUEL IN PAST
1. Has the vehicle run out of fuel in the past?
NO: CHECK FOR INTERMITTENT PROBLEMS (See CHECK FOR INTERMITTENT PROBLEMS )

YES: DTC CAUSED BY RUNNING OUT OF FUEL

INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

Disconnect the A3 A/F sensor connector.

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

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 (See REMOVAL )

Fig 2: Identifying A/F Sensor Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

OK: Go to Next Step

INSPECT EFI RELAY

Remove the EFI relay from the engine room relay block.

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

Standard resistance

TESTER CONNECTION SPECIFIED CONDITION CHART

Tester Connection	Specified Condition
3-5	10 kΩ or higher
3-5	Below 1 Ω (when battery voltage is applied to terminals 1 and 2)

Reinstall the EFI relay.

Fig 3: EFI Relay Circuit

NO: REPLACE EFI RELAY

OK: Go to Next Step

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

Disconnect the A3 A/F sensor connector.
Turn the ignition switch to the ON position.

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

Standard voltage

TESTER CONNECTION SPECIFIED CONDITION CHART

Tester Connection	Specified Condition
+B (A3-2) - Body ground	9 to 14 V

Turn the ignition switch off.
Disconnect the E8 ECM connector.

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

Fig 4: Disconnecting E8 ECM Connector

Standard resistance

TESTER CONNECTION SPECIFIED CONDITION CHART

Tester Connection	Specified Condition
HT (A3-1) - HA1A (E8-1)	Below 1 Ω
AF+ (A3-3) - A1A+ (E8-21)	Below 1 Ω
AF- (A3-4) - A1A- (E8-31)	Below 1 Ω
HT (A3-1) or HA1A (E8-1) - Body ground	10 kΩ or higher
AF+ (A3-3) or A1A+ (E8-21) - Body ground	10 kΩ or higher
AF- (A3-4) or A1A- (E8-31) - Body ground	10 kΩ or higher

Fig 5: A/F Sensor Circuit Diagram

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

NG: REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: Go to Next Step

CHECK AIR INDUCTION SYSTEM
1. Check the air induction system for vacuum leakage.
  OK:
  
  No leakage from air induction system.
NG: REPAIR OR REPLACE AIR INDUCTION SYSTEM

OK: Go to Next Step
CHECK PCV HOSE CONNECTIONS
OK:

PCV hose is connected correctly and is not damaged.

NG: REPAIR OR REPLACE PCV HOSE

OK: Go to Next Step
CHECK FUEL PRESSURE
1. Check the fuel pressure (See ON-VEHICLE INSPECTION ).
NG: REPAIR OR REPLACE FUEL SYSTEM

OK: Go to Next Step
INSPECT FUEL INJECTOR
1. Check the injector injection (whether fuel volume is high or low, and whether injection pattern is poor).
NG: REPLACE FUEL INJECTOR (See REMOVAL )

OK: 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)

Read the DTCs using the Techstream.

Enter the following menus: Powertrain/Engine and ECT/Trouble Codes.

Result

RESULT CHART

Display (DTC Output)	Proceed to
No output	A
P2A00	B

B: REPLACE ECM AND PERFORM CONFIRMATION DRIVING PATTERN

A: Go to Next Step

CONFIRM WHETHER VEHICLE HAS RUN OUT OF FUEL IN PAST
1. Has the vehicle run out of fuel in the past?
NO: CHECK FOR INTERMITTENT PROBLEMS (See CHECK FOR INTERMITTENT PROBLEMS )

YES: DTC CAUSED BY RUNNING OUT OF FUEL