Inspection Procedure

WARNING: This page is about a different car, the 2008 Toyota Yaris. However, it is still accessible from the selected car via links, so may be relevant.

HINT:

Read freeze frame data using a Techstream. 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.
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 a Techstream to the DLC3.
Turn the ignition switch to ON and turn the tester ON.
Select the following menu items: Powertrain / Engine and ECT / Trouble Codes.

Read DTCs.

Result

RESULT CHART

Display (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 (See DIAGNOSTIC TROUBLE CODE CHART )

A: Go to next step

PERFORM ACTIVE TEST USING TECHSTREAM (A/F CONTROL)

Connect the Techstream to the DLC3.
Start the engine.
Turn the tester ON.
Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
Select the following menu items: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.
Perform the Control the Injection Volume for A/F Sensor 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 Air-Fuel Ratio (A/F) sensor and the Heated Oxygen (HO2) sensor (AFS B1S1 and O2S B1S2) displayed on the tester.

HINT:

The Control the Injection Volume for A/F Sensor 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

VOLTAGE CHART

Tester 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 CHART

Status 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 leak 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 blockage or blockage Gas leak 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 Control the Injection Volume for A/F Sensor, 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 Control the Injection Volume for A/F Sensor, the AFS is consistently less than 3.0 V, and the O2S is consistently more than 0.55 V. Lean/Rich: During Control the Injection Volume for A/F Sensor of the Active Test, the output voltage of the heated oxygen sensor alternates correctly.

B: Go to step 11

C: Go to step 15

A: Go to next step

READ VALUE USING TECHSTREAM (COOLANT TEMP)
1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON and turn the tester ON.
3. Select the following menu items: Powertrain / Engine and ECT / Data List / All Data / Coolant Temp.
4. Read the Data List twice, when the engine is both cold and warmed up.
  Standard:
  
  With cold engine: Same as ambient air temperature.
  
  With warm engine: 75°C to 100°C (167°F to 212°F).
NG: REPLACE ENGINE COOLANT TEMPERATURE SENSOR (See REMOVAL )

OK: Go to next step
READ VALUE USING TECHSTREAM (MAF)
1. Read the values using the Techstream (MAF).
  NOTE:
  - Turn the ignition switch to OFF.
  - Perform the inspection with the vehicle indoors and on a level surface.
  - Perform the inspection of the mass air flow meter while it is installed in the air cleaner case (installed on the vehicle).
  - During the test, do not use an exhaust air duct to apply suction to the exhaust pipe.
  1. Connect the Techstream to the DLC3.
  2. Turn the ignition switch ON (do not start the engine).
  3. Turn the tester ON.
  4. Select the following menu items: Powertrain / Engine and ECT / Data List / MAF.
  5. Wait for 30 seconds, and read the values on the tester.
    Standard value:
    
    Less than 0.28 g/sec
2. Inspect the mass air flow meter.
  1. Remove the mass air flow meter (See REMOVAL ).
  2. Using a work light, check that the platinum filament (heater portion) in the mass air flow meter has no foreign matter attached.
    OK:
    
    No foreign matter attached
  3. Reinstall the mass air flow meter (See INSTALLATION ).
NG: REPLACE MASS AIR FLOW METER (See REMOVAL )

OK: 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
1. Check the air induction system for vacuum leak.
  OK:
  
  No leak from air induction system.
NG: REPAIR OR REPLACE AIR INDUCTION SYSTEM

OK: Go to next step
CHECK FOR SPARKS AND IGNITION (See INSPECTION PROCEDURE )
NG: REPAIR OR REPLACE IGNITION SYSTEM

OK: Go to next step
CHECK FOR EXHAUST GAS LEAK
1. Check for exhaust gas leak.
  OK:
  
  No gas leak.
NG: REPAIR OR REPLACE EXHAUST SYSTEM

OK: Go to next step
CHECK FUEL PRESSURE
1. Check the fuel pressure (See ON-VEHICLE INSPECTION ).
  Standard:
  
  304 to 343 kPa (3.1 to 3.5 kgf/cm ² , 44.1 to 49.7 psi)
NG: REPAIR OR REPLACE FUEL SYSTEM

OK: Go to next step
INSPECT FUEL INJECTOR (INJECTION AND VOLUME)
1. Check the injection volume (See INSPECTION ).
  Standard:
  
  45 to 58 cm ³ (2.9 to 3.5 cu in.) per 15 seconds
NG: REPLACE FUEL INJECTOR (See REMOVAL )

OK: Go to next step
INSPECT AIR-FUEL RATIO SENSOR (HEATER RESISTANCE) (See INSPECTION PROCEDURE )
NG: REPLACE AIR-FUEL RATIO SENSOR (See REMOVAL )

OK: Go to next step
INSPECT INTEGRATION RELAY (EFI RELAY) (See INSPECTION PROCEDURE )
NG: REPLACE INTEGRATION RELAY

OK: Go to next step
CHECK HARNESS AND CONNECTOR (A/F SENSOR - ECM) (See INSPECTION PROCEDURE )
NG: REPAIR OR REPLACE HARNESS OR CONNECTOR

OK: Go to next step
REPLACE AIR-FUEL RATIO SENSOR
1. Replace the A/F sensor (See REMOVAL ).
PERFORM CONFIRMATION DRIVING PATTERN

Fig 2: Identifying Vehicle Speed Graph
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON and turn the tester ON.
3. Clear DTCs (See DTC CHECK/CLEAR ).
4. Switch the ECM from normal mode to check mode using the tester (See CHECK MODE PROCEDURE ).
5. Start the engine and warm it up with all the accessories switched OFF.
6. Drive the vehicle at between 38 mph and 75 mph (60 km/h and 120 km/h) and at an engine speed of between 1,400 rpm and 3,200 rpm for 3 to 5 minutes.
  HINT:
  
  If the system is still malfunctioning, the MIL will be illuminated during step (f).
  
  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 tester, select the following menu items: Powertrain / Engine and ECT / Trouble Codes.

Read DTCs.

Result

RESULT CHART

Display (DTC Output)	Proceed To
No output	A
P0171 or P0172	B

B: Go to step 3

A: END