The AF sensor has an output delay of a few seconds and the 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

Output Voltage More than 3.35 V Less than 3.0 V

Output Voltage More than 0.5 V Less than 0.4 V

Output Voltage Almost no reaction

Output Voltage More than 0.5 V Less than 0.4 V

A/F sensor A/F sensor heater A/F sensor circuit

Output Voltage More than 3.35 V Less than 3.0 V

Output Voltage Almost no reaction

HO2 sensor HO2 sensor heater HO2 sensor circuit

Case

A/F Sensor (Sensor 1) Output Voltage

HO2 Sensor (Sensor 2) Output Voltage

Main Suspected Trouble Areas

Injection volume +25 % -12.5 %

Injection Volume +25 % -12.5 %

• Fuel pressure

• Gas leakage from exhaust system (Air-fuel ratio extremely lean or rich)

4

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 B1 S1 and O2S B1 S2; then press the YES button and then the ENTER button followed by the F4 button. 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 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.

• If the OX1B wire from the ECM connector is short-circuited to the +B wire, DTC P0138 will be set.

Do It Yourself Car Diagnosis

Do It Yourself Car Diagnosis

Don't pay hundreds of dollars to find out what is wrong with your car. This book is dedicated to helping the do it yourself home and independent technician understand and use OBD-II technology to diagnose and repair their own vehicles.

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