Inspection Procedure

HINT:

• 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.
• Malfunctioning areas can be found by performing 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 area are malfunctioning or not.
  1. Perform the ACTIVE TEST A/F CONTROL operation.
• The A/F CONTROL operation lowers the injection volume 12.5% or increases the injection volume 25%.
  1. Connect the intelligent tester to the DLC3.
  2. Turn the power switch ON (IG).
  3. Put the engine in inspection mode (See SFI SYSTEM  ).
  4. Warm up the engine by running the engine at 2,500 rpm, depressing the accelerator pedal more than 60% for approximately 90 seconds.
  5. Enter the following menus: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
  6. Perform the A/F CONTROL operation with the engine in an idle condition (press the right or left button).

Result: 

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

+25% → rich output: More than 0.55 V 

-12.5% → lean output: Less than 0.4 V 

Fig 1: A/F Sensor Voltage Output Graph

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

To display the graph, enter ACTIVE TEST / A/F CONTROL / USER DATA, select "AFS B1S1 and O2S B1S2" by pressing the "YES" button followed by the "ENTER" button and then press the "F4" button.

1. CHECK OTHER DTC OUTPUT (IN ADDITION TO DTC P0420) 
   1. Connect the intelligent tester to the DLC3.
   2. Turn the power switch ON (IG).
   3. Turn the intelligent tester ON.
   4. Enter the following menus: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.
   5. Read the DTCs.

      Result 

      ITEM CONTENTS
      
      

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

      HINT:

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

   B: GO TO DTC CHART 

   A: Go to next step 

2. INSPECT FOR EXHAUST GAS LEAK 

   OK: 

   No gas leakage. 

   NG: REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT 

   OK: Go to next step 

3. INSPECT AIR FUEL RATIO SENSOR (BANK 1 SENSOR 1) 

   NG: REPLACE AIR FUEL RATIO SENSOR 

   OK: Go to next step 

4. INSPECT HEATED OXYGEN SENSOR (BANK 1 SENSOR 2) 

   NG: REPLACE HEATED OXYGEN SENSOR 

   OK: REPLACE THREE-WAY CATALYTIC CONVERTER (REPLACE FRONT PIPE)