The Air Fuel Ratio AF sensor has an output delay of a few seconds and the Heated Oxygen HO sensor has a maximum output delay of approximately seconds

Case

A/F Sensor (Sensor 1) Output Voltage

HO2 Sensor (Sensor 2) Output Voltage

Main Suspected Trouble Areas

1

Injection Volume +25 % -12.5 %

Injection Volume +25 % -12.5 %

Output Voltage More than 3.35 V Less than 3.0 V

-LXTÏ

Output Voltage More than 0.5 V Less than 0.4 V

2

Injection Volume +25 % -12.5 %

♦ _TLr

Injection Volume +25 % -12.5 %

♦ _TLT

• A/F sensor circuit

Output Voltage Almost no reaction

-NG

Output Voltage More than 0.5 V Less than 0.4 V

Injection Volume +25 % -12.5 %

Injection Volume +25 % -12.5 %

• HO2 sensor heater

• HO2 sensor circuit

3

Output Voltage More than 3.35 V Less than 3.0 V

-LXTÏ

Output Voltage Almost no reaction

-NG

Case

A/F Sensor (Sensor 1) Output Voltage

HO2 Sensor (Sensor 2) Output Voltage

Main Suspected Trouble Areas

4

Injection volume +25 % -12.5 %

Injection Volume +25 % -12.5 %

• Fuel pressure

• Gas leakage from exhaust system

(Air-fuel ratio extremely lean or rich)

Output Voltage Almost no reaction

-NG

Output voltage Almost no reaction

-NG

• 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 B1S1 and O2S B1S2, 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.

• DTC P2A00 may also be set, when the sensor element is electrically clogged or contaminated.

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

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