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.

1. Connect an intelligent tester to the DLC3.
2. Start the engine and turn the tester ON.
3. Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
4. On the tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
5. Perform the A/F CONTROL operation with the engine idling (press the RIGHT or LEFT button to change the fuel injection volume).
6. Monitor the voltage outputs of the A/F and HO2 sensors (AFS B1 S1 and O2S B1 S2) 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%.
   • The sensors react in accordance with increases and decreases in the fuel injection volume.

Standard 

Case	A/F Sensor (Sensor 1) Output Voltage		HO2 Sensor (Sensor 2) Output Voltage		Main Suspected Trouble Areas
1	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	-
	Output Voltage More than 3.35 V Less than 3.0 V	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Output Voltage More than 0.5 V Less than 0.4 V	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	A/F sensor A/F sensor heater A/F sensor circuit
	Output Voltage Almost no reaction	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Output Voltage More than 0.5 V Less than 0.4 V	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
3	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	HO2 sensor HO2 sensor heater HO2 sensor circuit
	Output Voltage More than 3.35 V Less than 3.0 V	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Output Voltage Almost no reaction	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
4	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Injection Volume +25% -12.5%	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Injector Fuel pressure Gas leakage from exhaust system (Air-fuel ratio extremely lean or rich)
	Output Voltage Almost no reaction	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Output Voltage Almost no reaction	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 B1 S1 and O2S B1 S2, and press the YES button and then the ENTER button followed by the F4 button.

HINT:

• DTC P2A00 may be 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. Freeze frame data record the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, 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.

1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P2A00) 
   1. Connect an intelligent tester to the DLC3.
   2. Turn the ignition switch to ON.
   3. Turn the tester ON.
   4. Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.
   5. Read DTCs.

      Result 

      RESULT REFERENCE
      
      

      Display (DTC Output)	Proceed To
      P2A00	A
      P2A00 and other DTCs	B

      If any DTCs relating to the A/F sensor (DTCs for the A/F sensor heater or A/F sensor admittance) are output, troubleshoot those DTCs first.

   B: GO TO  DTC TABLE  

   A: GO TO NEXT STEP 

2. INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE) (See  INSPECTION PROCEDURE   ) 

   NG: REPLACE AIR FUEL RATIO SENSOR 

   OK: GO TO NEXT STEP 

3. CHECK HARNESS AND CONNECTOR (ECM - AIR FUEL RATIO SENSOR) (See  INSPECTION PROCEDURE   ) 

   NG: REPAIR OR REPLACE HARNESS OR CONNECTOR 

   OK: GO TO NEXT STEP 

4. PERFORM CONFIRMATION DRIVING PATTERN 

   NEXT: GO TO NEXT STEP 

5. CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00) 
   1. Connect the intelligent tester to the DLC3.
   2. Turn the ignition switch to ON and turn the tester ON.
   3. Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / PENDING CODES.
   4. Read pending DTCs.

      Result 

      RESULT REFERENCE
      
      

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

   B: CHECK FOR INTERMITTENT PROBLEMS 

   A: GO TO NEXT STEP 

6. REPLACE AIR FUEL RATIO SENSOR 

   NEXT: GO TO NEXT STEP 

7. PERFORM CONFIRMATION DRIVING PATTERN 

   NEXT: GO TO NEXT STEP 

8. CHECK WHETHER DTC OUTPUT RECURS (DTC P2A00) 
   1. Connect the intelligent tester to the DLC3.
   2. Turn the ignition switch to ON and turn the tester ON.
   3. Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / PENDING CODES.
   4. Read pending DTCs.

      Result 

      RESULT REFERENCE
      
      

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

   B: REPLACE ECM 

   A: END