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

1

Injection Volume +25 % -12.5 %

Injection Volume +25 % -12.5 %

-

Output Voltage More than 3.35 V Less than 3.0 V

-U-IÜ5

Output Voltage More than 0.5 V Less than 0.4 V

-TUBk

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

-TUBk

3

Injection Volume +25 % -12.5 %

Injection Volume +25 % -12.5 %

• HO2 sensor heater

• HO2 sensor circuit

Output Voltage More than 3.35 V Less than 3.0 V

"UTS

Output Voltage Almost no reaction

-NG

4

Injection volume +25 % -12.5 %

t_nu-

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 output voltages 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. Freeze frame data records 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.

INSPECT AIR-FUEL RATIO SENSOR (HEATER RESISTANCE) (See page ES-83)

REPLACE AIR-FUEL RATIO SENSOR

INSPECT INTEGRATION RELAY (EFI MAIN RELAY) (See page ES-84)

REPLACE INTEGRATION RELAY (EFI MAIN RELAY)

CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM) (See page ES-310)

REPAIR OR REPLACE HARNESS OR CONNECTOR

REPLACE AIR-FUEL RATIO SENSOR

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CHECK WHETHER DTC OUTPUT RECURS

(a) Connect the intelligent tester to the DLC3.

(b) Turn the ignition switch ON and turn the tester ON.

(d) Start the engine.

(e) Allow the engine to idle for 5 minutes or more.

(f) Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / PENDING CODES.

(g) Read pending DTCs.

Result

Display (DTC Output)

Proceed To

No output

A

P2238, P2239, P2252 or P2253

REPLACE ECM

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