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 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.
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 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 in the fuel injection volume.

Standard:

INJECTION VOLUME REFERENCE

Tester 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.

Fig 1: (A/F) Sensor And (HO2) 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, and press the YES button and then the ENTER button followed by the F4 button.

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 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)

Connect the intelligent tester to the DLC3.
Turn the ignition switch to the ON position.
Turn the tester on.
Enter the following menus: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.

Read the DTCs.

Result

DTC OUTPUT RESULT

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

A: go to next step

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

Connect the intelligent tester to the DLC3.
Start the engine.
Turn the tester 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: DIAGNOSIS / ENHANCED OBD II / SNAPSHOT / MANUAL SNAPSHOT / USER DATA/AFS B1S1 and ENGINE SPD.

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

VOLTAGE SPECIFIED CONDITION

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 2: Malfunction Graph

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 intelligent tester.

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

Result

DTC OUTPUT RESULT

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 intelligent tester.

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

Result

DTC OUTPUT RESULT

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

YES: DTC CAUSED BY RUNNING OUT OF FUEL

INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

Disconnect the A3 A/F sensor connector.

Fig 3: Identifying A3 A/F Sensor Connector Terminals

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

Standard resistance

RESISTANCE SPECIFIED CONDITIONS

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

NG: REPLACE AIR FUEL RATIO SENSOR (See REMOVAL )

OK: go to next step

INSPECT EFI RELAY (EFI)

Remove the EFI relay from the engine room relay block.

Fig 4: Inspecting EFI Relay

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

Standard resistance

RESISTANCE SPECIFIED CONDITIONS

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)

NG: REPLACE EFI RELAY

OK: go to next step

CHECK WIRE HARNESS (A/F SENSOR - ECM) AND (SENSOR POWER SOURCE)

Disconnect the A3 A/F sensor connector.

Fig 5: Identifying A/F Sensor And ECM Connector

Turn the ignition switch to the ON position.

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

Standard voltage

VOLTAGE SPECIFIED CONDITION

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.

Standard resistance

RESISTANCE SPECIFIED CONDITIONS

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 6: A/F Sensor Power Source - Circuit Diagram

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.
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

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 intelligent tester.

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

Result

DTC OUTPUT RESULT

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

YES: DTC CAUSED BY RUNNING OUT OF FUEL