Inspection Procedure

NOTE:

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, it is useful for determining whether the vehicle was running or stopped, the engine was warmed up or not, the air-fuel ratio was lean or rich, etc. at the time of the malfunction.

CHECK OTHER DTC OUTPUT(IN ADDITION TO DTC P0420)

Connect the hand-held tester or the OBD II scan tool to the DLC3.
Turn the ignition switch ON and push the hand-held tester or the OBD II scan tool main switch ON.
Select the item "DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES."

Read the DTCs.

Result:

DTC OUTPUT DISPLAY

Display (DTC output)	Proceed to
P0420	A
P0420 and other DTCs	B

NOTE:

If any other codes besides P0420 are output, perform the troubleshooting for those DTCs first.

B: GO TO RELEVANT DTC CHART (See DIAGNOSTIC TROUBLE CODE CHART )
A: Go to next step.

CHECK FOR EXHAUST GAS LEAKAGE
1. NG: REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT (See REMOVAL & INSTALLATION AND DISASSEMBLY & REASSEMBLY )
2. OK: Go to next step.
INSPECT HEATED OXYGEN SENSOR(BANK 1 SENSOR 1) (See DTC P0130 OXYGEN SENSOR CIRCUIT MALFUNCTION (BANK 1 SENSOR 1), DTC P2195 OXYGEN SENSOR SIGNAL STUCK LEAN (BANK 1 SENSOR 1), DTC P2196 OXYGEN SENSOR SIGNAL STUCK RICH (BANK 1 SENSOR 1) )
Refer to the hint below.
1. NG: REPLACE HEATED OXYGEN SENSOR
2. OK: Go to next step.
INSPECT HEATED OXYGEN SENSOR (BANK 1 SENSOR 2) (See DTC P0136 OXYGEN SENSOR CIRCUIT MALFUNCTION (BANK 1 SENSOR 2) )
Refer to the hint below.
1. NG: REPLACE HEATED OXYGEN SENSOR
2. OK: REPLACE THREE-WAY CATALYTIC CONVERTER(EXHAUST MANIFOLD)
NOTE:
Hand-held tester only:
- The following procedure enables the technician to identify a trouble area if malfunction in both front and rear heated oxygen sensors is other than the catalyst converter, or the malfunction that indicates the actual air-fuel ratio extremely RICH or LEAN.
- Narrowing down the trouble area is possible by performing "A/F CONTROL" ACTIVE TEST (heated oxygen sensor or other trouble areas can be distinguished).
"A/F CONTROL" is ACTIVE TEST which changes the injection volume -12.5 % or +25 %.
1. Connect the hand-held tester to the DLC3 on the vehicle.
2. Turn the ignition switch ON.
3. Warm up the engine by running the engine at 2,500 RPM for approximately 90 seconds.
4. Select the item "DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL."
5. Perform "A/F CONTROL" with the engine in an idle condition (press the right or left button).
  Result:
  
  Heated oxygen sensor reacts in accordance with increase and decrease of injection volume
  
  +25 % --> rich output: More than 0.5 V
  
  -12.5 % --> lean output: Less than 0.4 V
  
  NOTE: There is a delay of few seconds in the sensor 1 (front sensor) output, and there is about 20 seconds delay at maximum in the sensor 2 (rear sensor)
  
  Fig 1: Graphical Representation Output Voltage Of Heated Oxygen Sensor
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
The following of the A/F CONTROL procedure enables the technician to check and graph the voltage outputs of both the heated oxygen sensors.

For displaying the graph indication, enter "ACTIVE TEST / A/F CONTROL / USER DATA," then select "O2S B1S1 and O2S B1S2" by pressing "YES" button and push "ENTER" button before pressing "F4" button.