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 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.
On the tester, 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 OS2 B1S2) 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

TESTER DISPLAY FUNCTIONS

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

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, select the following menu items on the tester: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL / USER DATA / AFS B1S1 and O2S B1S2, 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 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 or OBD II scan tool. 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 an intelligent tester or OBD II scan tool to the DLC3.
Turn the ignition switch to ON.
Turn the tester or scan tool ON.
On the tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.
If using an OBD II scan tool, refer to the instruction manual.

Read DTCs.

Result

DTC RESULT DESCRIPTION

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 OF INTELLIGENT TESTER OR OBD II SCAN TOOL (OUTPUT VOLTAGE OF A/F SENSOR)

Connect an intelligent tester or OBD II scan tool to the DLC3.
Start the engine.
Turn the tester or scan tool ON.
Warm up the Air-Fuel Ratio (A/F) sensor at an engine speed of 2,500 rpm for 90 seconds.
On the tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / SNAPSHOT / MANUAL SNAPSHOT / USER DATA / AFS B1S1 and ENGINE SPD.
If using an OBD II scan tool, refer to the instruction manual.

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

While idling (check for at least 30 seconds) (Step (1)).
At an engine speed of approximately 2,500 rpm (without any sudden changes in engine speed) (Step (2)).
Raise the engine speed to 4,000 rpm and then quickly release the accelerator pedal so that the throttle valve is fully closed (Step (3)).

Standard voltage

STANDARD VOLTAGE SPECIFICATIONS

Conditions	A/F Sensor Voltage Variations	Reference
Steps (1) and (2)	Changes at approx. 3.3 V (0.66 V*)	Between 3.1 V (0.62 V) and 3.5 V (0.7 V)
Step (3)	Increases to 3.8 V (0.76 V) or more	This occurs during engine deceleration (when fuel-cut performed)
HINT: *: Voltage when using the OBD II scan tool. For more information, see the diagrams below.

Fig 2: Identifying A/F Sensor Normal And Malfunction Conditions

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

HINT:

If the output voltage of the A/F sensor remains at approximately 3.3 V (0.66 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 (0.76 V*) or more, or 2.8 V (0.56 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 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 (0.56 V*) during fuel enrichment. For the vehicle, this translates 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.
* Voltage when using the OBD II scan tool.

NG: Go to step 9

OK : Go to Next Step

PERFORM CONFIRMATION DRIVING PATTERN

CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00)

Read DTCs using the intelligent tester or OBD II scan tool.
If using an intelligent tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.

If using an OBD II scan tool, refer to the instruction manual.

Result

DTC RESULT DESCRIPTION

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.
PERFORM CONFIRMATION DRIVING PATTERN

CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00)

Read DTCs using the intelligent tester or OBD II scan tool.
If using an intelligent tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.

If using an OBD II scan tool, refer to the instruction manual.

Result

DTC RESULT DESCRIPTION

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

NOTE: When replacing the ECM, perform confirmation driving pattern (See READINESS MONITOR DRIVE PATTERN ).

B: REPLACE ECM

A: Go to Next Step

CONFIRM IF VEHICLE HAS RUN OUT OF FUEL IN PAST
NO : CHECK FOR INTERMITTENT PROBLEMS

YES : DTC CAUSED BY RUNNING OUT OF FUEL

INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)

Disconnect the A24 A/F sensor connector.

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

Standard resistance

RESISTANCE SPECIFICATIONS

Tester Connections	Specified Conditions
HT (1) - +B (2)	Between 1.8 Ω and 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

Fig 3: Identifying A24 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 R/B.

Check the EFI relay resistance.

Standard resistance

RESISTANCE SPECIFICATIONS

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

NG: REPLACE EFI RELAY

OK : Go to Next Step

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

Disconnect the A24 A/F sensor connector.
Turn the ignition switch to ON.

Measure the voltage between the +B terminal of the A/F sensor connector and body ground.

Standard voltage

STANDARD VOLTAGE SPECIFICATIONS

Tester Connections	Specified Conditions
+B (A24-2) - Body ground	Between 9 V and 14 V

Turn the ignition switch to OFF.
Disconnect the E4 ECM connector.

Check the resistance.

Standard resistance (Check for open)

STANDARD RESISTANCE SPECIFICATIONS FOR OPEN

Tester Connections	Specified Conditions
HT (A24-1) - HA1A (E4-5)	Below 1 Ω
AF+ (A24-3) - A1A+ (E4-23)	Below 1 Ω
AF- (A24-4) - A1A- (E4-31)	Below 1 Ω

Standard resistance (Check for short)

STANDARD RESISTANCE SPECIFICATIONS (FOR SHORT)

Tester Connections	Specified Conditions
HT (A24-1) or HA1A (E4-5) - Body ground	10 kΩ or higher
AF+ (A24-3) or A1A+ (E4-23) - Body ground	10 kΩ or higher
AF- (A24-4) or A1A- (E4-31) - Body ground	10 kΩ or higher

Fig 5: Checking Harness And Connector (A/F Sensor - ECM)

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 ASSEMBLY
1. Check the injector injection (whether fuel volume is high or low, and whether injection pattern is poor) (See INSPECTION ).
NG: INSPECT FUEL INJECTOR ASSEMBLY

OK : Go to Next Step
REPLACE AIR FUEL RATIO SENSOR
1. Replace the air-fuel ratio sensor.
PERFORM CONFIRMATION DRIVING PATTERN

CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00)

Read DTCs using the intelligent tester or OBD II scan tool.
If using an intelligent tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.

If using an OBD II scan tool, refer to the instruction manual.

Result

DTC RESULT DESCRIPTION

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

NOTE: When replacing the ECM, perform confirmation driving pattern (See READINESS MONITOR DRIVE PATTERN ).

B: REPLACE ECM

A: Go to Next Step

CONFIRM IF VEHICLE HAS RUN OUT OF FUEL IN PAST
NO : CHECK FOR INTERMITTENT PROBLEMS

YES : DTC CAUSED BY RUNNING OUT OF FUEL