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 the intelligent tester.
- Connect the intelligent tester to the DLC3.
- Start the engine and turn the tester on.
- Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
- On the tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/ F CONTROL.
- Perform the A/F CONTROL operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).
- Monitor the voltage outputs of the A/F and HO2 sensors (AFS B1S1 and OS2 B1S2) 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%.
- Each sensor reacts in accordance with increases and decreases in the fuel injection volume.
Standard:
DATA LISTTester Display (Sensor) Injection Volume Status Voltage AFS B1S1 (A/F) +25% Rich Less than 3.0 AFS B1S1 (A/F) -12.5% Lean More than 3.35 O2S B1S2 (HO2) +25% Rich More than 0.55 O2S B1S2 (HO2) -12.5% Lean Less than 0.4
| Case | A/F Sensor (Sensor 1) Output Voltage | HO2 Sensor (Sensor 2) Output Voltage | Main Suspected Trouble Area | ||
|---|---|---|---|---|---|
| 1 | Injection Volume +25 % -12.5% |
Injection Volume +25 % -12.5% |
- | ||
| Output Voltage More than 3.35 V Less than 3.0 V |
Output Voltage More than 0.55 V Less than 0.4 V |
||||
| 2 | Injection Volume +25 % -12.5% |
Injection Volume +25 % -12.5 % |
|
||
| Output Voltage Almost no reaction |
Output Voltage More than 0.55 V Less than 0.4 V |
||||
| 3 | Injection Volume +25 % -12.5% |
Injection Volume +25 % -12.5% |
|
||
| Output Voltage More than 3.35 V Less than 3.0 V |
Output Voltage Almost no reaction |
||||
| 4 | Injection Volume +25 % -12.5% |
Injection Volume +25 % -12.5% |
|
||
| Output Voltage Almost no reaction |
Output Voltage Almost no reaction |
||||
- 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:
- Read freeze frame data using the intelligent tester. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, 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.
- 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.
- CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0171 OR P0172)
- Connect the intelligent tester to the DLC3.
- Turn the ignition switch to the ON position and turn the tester on.
- Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.
- Read the DTCs.
Result
DTC RESULT REFERENCEDisplay (DTC Output) Proceed to P0171 or P0172 A P0171 or P0172 and other DTCs B HINT:
If any DTCs other than P0171 or P0172 are output, troubleshoot those DTCs first.
B: GO TO DTC CHART
A: GO TO NEXT STEP
- CHECK PCV HOSE CONNECTIONS
OK:
PCV hose is connected correctly, and is not damaged.
NG: REPAIR OR REPLACE PCV HOSE
OK: GO TO NEXT STEP
- CHECK AIR INDUCTION SYSTEM
- Check the air induction system for vacuum leakage.
OK:
No leakage from air induction system.
NG: REPAIR OR REPLACE AIR INDUCTION SYSTEM
OK: GO TO NEXT STEP
- Check the air induction system for vacuum leakage.
- PERFORM ACTIVE TEST USING INTELLIGENT TESTER (A/F CONTROL)
- Connect the intelligent tester to the DLC3.
- Start the engine and turn the tester on.
- Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
- On the tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / ACTIVE TEST / A/F CONTROL.
- Perform the A/F CONTROL operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).
- Monitor the voltage outputs of A/F and HO2 sensors (AFS B1S1 and O2S B1S2) 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%.
- Each sensor reacts in accordance with increases and decreases in the fuel injection volume.
Standard
DATA LISTTester Display (Sensor) Injection Volume Status Voltage AFS B1S1 (A/F) +25% Rich Less than 3.0 AFS B1S1 (A/F) -12.5% Lean More than 3.35 O2S B1S2 (HO2) +25% Rich More than 0.55 O2S B1S2 (HO2) -12.5% Lean Less than 0.4 Result
RESULT REFERENCEStatus AFS B1S1 Status O2S B1S2 A/F Condition and A/F Sensor Condition Misfire Suspected Trouble Area Proceed to Lean/Rich Lean/Rich Normal - - C Lean Lean Actual air-fuel ratio lean May occur - PCV valve and hose
- PCV hose connections
- Injector blockage
- Gas leakage from exhaust system
- Air induction system
- Fuel pressure
- Mass Air Flow (MAF) meter
- Engine Coolant Temperature (ECT) sensor
A Rich Rich Actual air-fuel ratio rich - - Injector leakage or blockage
- Gas leakage from exhaust system
- Ignition system
- Fuel pressure
- MAF meter
- ECT sensor
A Lean Lean/Rich A/F sensor malfunction - A/F sensor B Rich Lean/Rich A/F sensor malfunction - A/F sensor B Lean: During A/F CONTROL, the A/F sensor output voltage (AFS) is consistently more than 3.35 V, and the HO2 sensor output voltage (O2S) is consistently less than 0.4 V.
Rich: During A/F CONTROL, the AFS is consistently less than 3.0 V, and the O2S is consistently more than 0.55 V.
B: Go to step 11
C: Go to step 15
A: GO TO NEXT STEP
- READ VALUE USING INTELLIGENT TESTER (COOLANT TEMP)
- Connect the intelligent tester to the DLC3.
- Turn the ignition switch to the ON position and turn the tester on.
- Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DATA LIST / ALL / COOLANT TEMP.
- Read the COOLANT TEMP twice, when the engine is cold and also when warmed up.
Standard:
With cold engine:
Same as ambient air temperature
With warm engine:
Between 75°C and 95°C (167°F and 203°F)
NG: REPLACE ENGINE COOLANT TEMPERATURE SENSOR
OK: GO TO NEXT STEP
- READ VALUE USING INTELLIGENT TESTER (MAF)
- Connect the intelligent tester to the DLC3.
- Turn the ignition switch to the ON position and turn the tester on.
- Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DATA LIST / ALL / MAF and COOLANT TEMP.
- Allow the engine to idle until the COOLANT TEMP reaches 75°C (167°F) or more.
- Read the MAF with the engine in an idling condition and at an engine speed of 2,500 rpm.
Standard:
MAF while engine idling:
Between 0.54 gm/s and 4.33 gm/s (shift position: N; A/C: OFF)
MAF at engine speed of 2,500 rpm:
Between 0.58 gm/s and 4.67 gm/s (shift position: N; A/C: OFF)
NG: REPLACE MASS AIR FLOW METER
OK: GO TO NEXT STEP
- CHECK FUEL PRESSURE
- Check the fuel pressure (See ON-VEHICLE INSPECTION ).
NG: REPAIR OR REPLACE FUEL SYSTEM
OK: GO TO NEXT STEP
- INSPECT FOR EXHAUST GAS LEAK
OK:
No gas leakage.
NG: REPAIR OR REPLACE EXHAUST SYSTEM
OK: GO TO NEXT STEP
- CHECK FOR SPARK AND IGNITION
HINT:
If the spark plugs or ignition system malfunctions, engine misfire may occur. The misfire count can be read using the intelligent tester. Select the following menu items:
DIAGNOSIS / ENHANCED OBD II / DATA LIST / ALL / CYL #1 (to CYL #4).
NG: REPAIR OR REPLACE IGNITION SYSTEM
OK: GO TO NEXT STEP
- INSPECT FUEL INJECTOR (INJECTION AND VALVE)
HINT:
If the injectors malfunction, engine misfire may occur. The misfire count can be read using the intelligent tester. Select the following menu items: DIAGNOSIS / ENHANCED OBD I / DATA LIST / ALL / CYL #1 (to CYL #4).
NG: REPLACE FUEL INJECTOR
OK: GO TO NEXT STEP
- INSPECT AIR FUEL RATIO SENSOR (HEATER RESISTANCE)
- Disconnect the A3 Air-Fuel Ratio (A/F) sensor connector.
- Measure the resistance according to the value (s) in the table below.
Standard resistance
AIR FUEL RATIO SENSOR TESTER CONNECTION AND SPECIFIED CONDITIONTester Connection Specified Condition HT (1) - +B (2) 1.8 to 3.4 Ω at 20°C (68°F) HT (1) - AF- (4) 10 kΩ or higher
NG: REPLACE AIR FUEL RATIO SENSOR
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
OK: GO TO NEXT STEP
- INSPECT EFI RELAY
- Remove the EFI relay from the engine room relay block.
- Measure the resistance according to the value (s) in the table below.
Standard resistance
EFI RELAY TESTER CONNECTION AND SPECIFIED CONDITIONTester Connection Specified Condition 3-5 10 kΩ or higher 3-5 Below 1 Ω (when battery voltage Is applied to terminals 1 and 2) - Reinstall the EFI relay.
NG: REPLACE EFI RELAY
OK: GO TO NEXT STEP
- CHECK WIRE HARNESS (A/F SENSOR - ECM) AND (SENSOR POWER SOURCE)
- Disconnect the A3 A/F sensor connector.
- Turn the ignition switch to the ON position.
- Measure the voltage according to the value (s) in the table below.
Standard voltage
WIRE HARNESS TESTER CONNECTION AND SPECIFIED CONDITIONTester Connection Specified Condition +B (A3-2) - Body ground 9 to 14 V - Turn the ignition switch off.
- Disconnect the E8 ECM connector.
- Measure the resistance according to the value (s) in the table below.
Standard resistance
WIRE HARNESS TESTER CONNECTION AND SPECIFIED CONDITIONTester Connection Specified Condition HT (A3-1) - HA1A (E8-1) Below 1 Ω AF+ (A3-3) - A1A+ (E8-21) Below 1 Ω AF- (A3-4) - A1A- (E8-31) Below 1 Ω HT (A3-1) or HA1A (E8-1) - Body ground 10 kΩ or higher AF+ (A3-3) or A1A+ (E8-21) - Body ground 10 kΩ or higher AF- (A3-4) or A1 A- (E8-31) - Body ground 10 kΩ or higher
NG: REPAIR OR REPLACE HARNESS OR CONNECTOR
OK: GO TO NEXT STEP
- REPLACE AIR FUEL RATIO SENSOR
- PERFORM CONFIRMATION DRIVING PATTERN
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
- Connect the intelligent tester to the DLC3.
- Turn the ignition switch to the ON position and turn the tester on.
- Clear the DTCs (See DTC CHECK / CLEAR ).
- Switch the ECM from normal mode to check mode using the tester (See CHECK MODE PROCEDURE ).
- Start the engine and warm it up with all the accessories switched off (Procedure "A").
- Drive the vehicle at between 38 mph to 75 mph (60 km/h to 120 km/h) and at an engine speed of between 1,400 rpm and 3,200 rpm for 3 to 5 minutes (Procedure "B").
HINT:
If the system is still malfunctioning, the MIL will be illuminated during Procedure "A".
NOTE: If the conditions in this test are not strictly followed, no malfunction will be detected.
- CHECK WHETHER DTC OUTPUT RECURS (DTC P0171 OR P0172)
- On the intelligent tester, select the following menu items: DIAGNOSIS / ENHANCED OBD II / DTC INFO / CURRENT CODES.
- Read the DTCs.
Result
DTC RESULT REFERENCEDisplay (DTC Output) Proceed to No output A P0171 or P0172 B
B: Go to step 5
A: END