Inspection Procedure

HINT:

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, as well as other data from the time when a malfunction occurred.

1. Are there any other codes (besides DTC P0420) being output? 

   PREPARATION: 

   1. Connect the hand-held tester or the OBD II scan tool to the DLC3.
   2. Turn the ignition switch ON and push the hand-held tester or the OBD II scan tool main switch ON.
   3. When using the hand-held tester, enter the following menus: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.

   CHECK: 

   Read the DTCs using the hand-held tester or the OBD II scan tool.

   RESULT: 

   DTC OUTPUT DISPLAY
   
   

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

   HINT:

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

   1. B : Go to relevant DTC chart (See  DIAGNOSTIC TROUBLE CODE CHART  ). 
   2. A : Go To Next Step 
2. Check gas leakage on exhaust system. 
   1. NG : Repair or replace exhaust gas leakage point. 
   2. OK : Go To Next Step 
3. Check oxygen sensor (bank 1 sensor 1) (See  DTC P0031 Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 1), DTC P0032 Oxygen Sensor Heater Control Circuit High (Bank 1 Sensor 1), DTC P0037 Oxygen Sensor Heater Control Circuit Low (Bank 1 Sensor 2), DTC P0038 Oxygen Sensor Heater Control Circuit High (Bank 1 Sensor 2), DTC P0051 Oxygen Sensor Heater Control Circuit Low (Bank 2 Sensor 1), DTC P0052 Oxygen Sensor Heater Control Circuit High (Bank 2 Sensor 1)  ). 

   HINT:

   Refer to the hint following the end of this flowchart.

   1. NG : Replace heated oxygen sensor. 
   2. OK : Replace front and rear three-way catalytic converter. 

   HINT:

   Hand-held tester only:

   • The following procedures enable a technician to identify the problem area if: 1) there is a malfunction in both the front and rear heated oxygen sensors but no malfunction in the catalyst converter, or 2) the actual air-fuel ratio is 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).

   Perform the ACTIVE TEST's A/F CONTROL operation.

   HINT:

   "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 speed 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: 

   1. Heated oxygen sensor reacts in accordance with increase and decrease of injection volume 
   2. +25 % --> rich output: More than 0.5 V 
   3. -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: Active Test Result Table

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

   To display the graph, enter the following menus: ACTIVE TEST / A/F CONTROL / USER DATA. Then select O2S B1S1 and O2S B1S2 by pressing YES. Finally, push ENTER and F4.

   NOTE: If the vehicle is short of fuel, the air-fuel ratio becomes LEAN and DTCs P0133 and/or P0153 will be recorded, and the MIL then comes on.