Inspection Procedure

HINT:

Hand-held tester only:

It is possible the malfunctioning area can be found using the ACTIVE TEST A/F CONTROL operation. The A/F CONTROL operation can determine if the A/F sensor, heated oxygen sensor or other potential trouble areas are malfunctioning or not.

Perform the ACTIVE TEST A/F CONTROL operation.

HINT:

A/F CONTROL operation lowers the injection volume 12.5% or increases the injection volume 25%.

Connect the hand-held tester to the DLC3 on the vehicle.
Turn the ignition switch ON.
Warm up the engine with the engine speed at 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 idle (press the right or left button).
Result:

A/F sensor reacts in synchronizing with increase and decrease of injection volume

+25 % --> rich output: Less than 3.0 V

-12.5 % --> lean output: More than 3.35 V

Heated oxygen sensor reacts in synchronizing with increase and decrease of injection volume

+25 % --> rich output: More than 0.55 V

-12.5 % --> lean output: Less than 0.4 V

NOTE: However, there is a few second delay in the A/F sensor output. And there is about 20 seconds delay in the heated oxygen sensor.

Fig 1: A/F Sensor Output Diagram

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

The following A/F CONTROL procedure enables a technician to check and graph the voltage outputs of both the A/F sensor and the heated oxygen sensor.

For displaying the graph, enter "ACTIVE TEST / A/F CONTROL / USER DATA", select "AFS B1S1 and O2S B1S2" by pressing "YES" and push "ENTER". Then press "F4".

HINT:

DTC P2A00 may be also detected, 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 hand-held tester or the OBD II scan tool. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, 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.

Are there any other codes (besides DTC P2A00) being output?
1. YES : Go to relevant DTC chart (see DIAGNOSTIC TROUBLE CODE CHART ).
2. NO : Go to next step.
Connect hand-held tester or OBD II scan tool, and read value for voltage output of A/F sensor.
PREPARATION:
1. Connect the hand-held tester or the OBD II scan tool to the DLC 3.
2. Warm up the A/F sensor (bank 1 sensor 1) with the engine at 2,500 RPM for approximately 90 seconds.
3. Read the A/F sensor voltage on the hand-held tester or OBD II scan tool.
CHECK:
1. Hand-held tester only:
  On the hand-held tester, enter the following menus: DIAGNOSIS / ENHANCED OBD II / SNAPSHOT / MANUAL SNAPSHOT / USER DATA. Read the values.
2. Select "AFS B1 S1/ENGINE SPD" and press button "YES".
3. Monitor the A/F sensor voltage carefully.
4. Check the A/F sensor voltage under the condition as follows.
  1. Allow the engine to idle for 30 seconds.
  2. Engine is racing at approximately 2,500 RPM (when engine revolution is not suddenly changed).
  3. Raise the engine speed to 4,000 RPM and release the accelerator pedal fully quickly.
OK:

Standard:

Conditions (1) and (2)

Voltage changes a little in the vicinity of 3.3 V (0.66 V)* (between approximately 3.1 to 3.5 V) as shown in the illustration.

Condition (3)

A/F ratio sensor voltage increases to 3.8 V (0.76 V)* or more during engine deceleration (when fuel cut) as shown in the illustration.

Fig 2: A/F Sensor Condition Graph
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

HINT:
- Whenever the A/F sensor output voltage remains at approximately 3.3 V (0.660 V)* (see "Malfunction Condition" graphic) under any condition as well as the above conditions, the A/F sensor may have an open-circuit. This will happen also when the A/F sensor heater has an open-circuit.
- Whenever the A/F sensor output voltage remains at a certain value of approximately 3.8 V (0.76 V)* or more, or 2.8 V (0.56 V)* or less (see "Malfunction Condition" graphic) under any condition as well as the above conditions, the A/F sensor may have a short-circuit.
- The ECM will stop fuel injection (fuel is cut) during engine deceleration. This will cause a LEAN condition and should result in a momentary increase in the A/F sensor output voltage.
- The ECM must establish a closed throttle position learned value to perform fuel cut. If the battery terminal has been disconnected, the vehicle must be driven over 16 km/h (10 mph) to allow the ECM to relearn the closed throttle position.
- When the vehicle is driven:
  The output voltage of the A/F sensor may be below 2.8 V (0.76 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, and therefore the current is converted into voltage inside the ECM. If measuring voltage at connectors of the A/F sensor or ECM, you will observe a constant voltage.
*: Voltage when using the OBD II scan tool.
1. OK : Go to step 14 .
2. NG : Go to next step.
Check resistance of A/F sensor heater (see INSPECTION ).
1. NG : Replace A/F sensor.
2. OK : Go to next step.

Check EFI main relay.

PREPARATION:

Remove the EFI main relay from the engine room J/B.

CHECK:

Inspect the EFI main relay.

OK:

EFI RELAY

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)

Fig 3: Identifying EFI Main Relay

NG : Replace EFI main relay.
OK : Go to next step.

Check for open and short in wire harness between ECM and A/F sensor (see HOW TO USE THE DIAGNOSTIC CHART AND INSPECTION PROCEDURE in INTRODUCTION article).
References: Bank 1 Sensor 1 System Drawing

Fig 4: A/F Sensor Wiring Diagram
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
1. NG : Repair or replace harness and connector.
2. OK : Go to next step.
Check air induction system (see SFI SYSTEM ).
CHECK:

Check for vacuum leaks in the air induction system.
1. NG : Repair or replace.
2. OK : Go to next step.
Check connection of PCV hose.
1. NG : Repair or replace PCV hose.
2. OK : Go to next step.
Check fuel pressure (see Check fuel pressure (see ON-VEHICLE INSPECTION ).
CHECK:

Check fuel pressure (high or low fuel pressure)
1. NG : Check and repair fuel pump, fuel pipe line and filter.
2. OK : Go to next step.
Check injector injection (see INSPECTION ).
CHECK:

Check injector injection (high or low fuel injection quantity or poor injection pattern).
1. NG : Replace injector.
2. OK : Go to next step.
Replace A/F sensor.
1. GO : Go to next step.
Perform confirmation driving pattern (see CONFIRMATION DRIVING PATTERN under DTC P2195: OXYGEN (A/F) SENSOR SIGNAL STUCK LEAN (BANK 1 SENSOR 1), DTC P2196: OXYGEN (A/F) SENSOR SIGNAL STUCK RICH (BANK 1 SENSOR 1).
HINT:

Clear all DTCs prior to performing the confirmation driving pattern.
1. GO : Go to next step.
Is there DTC P2A00 being output again?
1. YES : Replace ECM (see COMPONENTS ) and perform confirmation driving pattern.
2. NO : Go to next step.
Confirm if vehicle has run out of fuel in past?
1. NO : Check for intermittent problems (see PRE-CHECK ).
2. YES : DTC P2A00 is caused by running out of fuel.
Perform confirmation driving pattern (see CONFIRMATION DRIVING PATTERN under DTC P2195: OXYGEN (A/F) SENSOR SIGNAL STUCK LEAN (BANK 1 SENSOR 1), DTC P2196: OXYGEN (A/F) SENSOR SIGNAL STUCK RICH (BANK 1 SENSOR 1).
HINT:

Clear all DTCs prior to performing the confirmation driving pattern.
1. GO : Go to next step.
Is there DTC P2A00 being output again?
1. NO : Go to step 19 .
2. YES : Go to next step.
Replace A/F sensor.
1. GO : Go to next step.
Perform confirmation driving pattern (see CONFIRMATION DRIVING PATTERN under DTC P2195: OXYGEN (A/F) SENSOR SIGNAL STUCK LEAN (BANK 1 SENSOR 1), DTC P2196: OXYGEN (A/F) SENSOR SIGNAL STUCK RICH (BANK 1 SENSOR 1).
HINT:

Clear all DTCs prior to performing the confirmation driving pattern.
1. GO : Go to next step.
Is there DTC P2A00 being output again?
1. YES : Replace ECM (see COMPONENTS ).
2. NO : Go to next step.
Confirm if vehicle has run out of fuel in past?
1. NO : Check for intermittent problems (see PRE-CHECK ).
2. YES : DTC P2A00 is caused by running out of fuel.