Inspection Procedure

HINT:

It is possible that the malfunctioning area can be found using the Active Test Control the Injection Volume for A/F Sensor operation. The Active Test can determine if the heated oxygen sensor or other potential trouble areas are malfunctioning or not.

The injection volume can be switched to -12.5% (decrease) or +25% (increase) by the Active Test.

The Active Test procedure enables a technician to check and graph the output voltage of the heated oxygen sensors.

Procedure:

Connect the Techstream to the DLC3.
Turn the ignition switch ON.
Warm up the engine by running the engine at 2500 rpm for approximately 90 seconds.
Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.

Perform the Active Test while the engine is idling.

Standard:

The heated oxygen sensor reacts in accordance with the increase and decrease of injection volume:

+25% → Rich output: More than 0.55 V

-12.5% → Lean output: Less than 0.4 V

NOTE: The heated oxygen sensor (sensor 1) output has a few seconds of delay and the heated oxygen sensor (sensor 2) output has a maximum of 20 seconds of delay.
If the vehicle is short on fuel, the air-fuel ratio becomes lean and the DTCs will be recorded.

FRONT HO2 SENSOR VOLTAGE CHART

Case	Front HO2 Sensor (Sensor 1) Output Voltage	Rear HO2 Sensor (Sensor 2) Output Voltage	Main Suspected Trouble Area
1	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	-
2	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Front HO2 sensor Front HO2 sensor heater Front HO2 sensor circuit
3	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Rear HO2 sensor Rear HO2 sensor heater Rear HO2 sensor circuit
4	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002	Injector Fuel pressure Gas leakage from exhaust system (Air-fuel ratio extremely rich or lean)

HINT:

Read freeze frame data using the Techstream. 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 high heated oxygen sensor (sensor 1) voltage (0.55 V or more) indicates a rich air-fuel ratio.
A low heated oxygen sensor (sensor 1) voltage (0.4 V or less) indicates a lean air-fuel ratio.

CHECK OTHER DTC OUTPUT (IN ADDITION TO DTC P0171, P0172, P0174, P0175)

Connect the Techstream to the DLC3.
Turn the ignition switch ON and turn the tester ON.
Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

Read the DTCs.

Result

RESULT CHART

Display (DTC output)	Proceed to
P0171, P0172, P0174 or P0175	A
P0171, P0172, P0174 or P0175 and other DTCs	B

B: GO TO RELEVANT DTC CHART

A: Go to Next Step

CHECK CONNECTION OF PCV HOSE
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 leaks.
  NG: REPAIR OR REPLACE AIR INDUCTION SYSTEM
  
  OK: Go to Next Step

PERFORM ACTIVE TEST BY TECHSTREAM (A/F CONTROL)

Perform the Active Test Control the Injection Volume for A/F Sensor with the Techstream and check the heated oxygen sensor status.

Standard voltage:

Heated oxygen sensor reacts in accordance with the increase and decrease of injection volume:

+25% → Rich output: More than 0.55 V

-12.5% → Lean output: Less than 0.4 V

HEATED OXYGEN SENSOR SPECIFICATIONS

Related DTCs	Heated Oxygen Sensor Status				A/F Condition and Heated Oxygen Sensor Condition	Misfire	Main Suspected Trouble Area	Go to Step
Related DTCs	B1S1	B1S2	B2S1	B2S2	A/F Condition and Heated Oxygen Sensor Condition	Misfire	Main Suspected Trouble Area	Go to Step
N/A	L/R	L/R	L/R	L/R	Normal	None	None	N/A
P0171 P0174	L	L	L	L	Actual A/F is lean at all cylinders	May occur	PCV hose, air induction system, fuel pressure, MAF or ECT	A
P0172 P0175	R	R	R	R	Actual A/F is rich at all cylinders	None	Fuel pressure, MAF or ECT	A
P0171	L	L	L/R	L/R	Actual A/F is lean at bank 1	May occur	Spark plug, ignition system, injector or exhaust gas leak	B
P0174	L/R	L/R	L	L	Actual A/F is lean at bank 2	May occur	Spark plug, ignition system, injector or exhaust gas leak	B
P0172	R	R	L/R	L/R	Actual A/F is rich at bank 1	None	Spark plug, ignition system or injector	C
P0175	L/R	L/R	R	R	Actual A/F is rich at bank 2	None	Spark plug, ignition system or injector	C
P0171	L	R	L/R	L/R	Heated oxygen sensor (bank 1 sensor 1) malfunction	None	Heated oxygen sensor (bank 1 sensor 1)	D
P0174	L/R	L/R	L	R	Heated oxygen sensor (bank 2 sensor 1) malfunction	None	Heated oxygen sensor (bank 2 sensor 1)
P0172	R	L	L/R	L/R	Heated oxygen sensor (bank 1 sensor 1) malfunction	None	Heated oxygen sensor (bank 1 sensor 1)
P0175	L/R	L/R	R	L	Heated oxygen sensor (bank 2 sensor 1) malfunction	None	Heated oxygen sensor (bank 2 sensor 1)

HINT:

L: During Control the Injection Volume for A/F Sensor of the Active Test, the output voltage of the heated oxygen sensor almost always indicates 0.4 V or less (lean).

R: During Control the Injection Volume for A/F Sensor of the Active Test, the output voltage of the heated oxygen sensor almost always indicates 0.5 V or more (rich).

B: Go to step 8

C: Go to step 10

D: Go to step 11

A: Go to Next Step

READ VALUE OF TECHSTREAM (COOLANT TEMP)
1. Connect the Techstream to the DLC3.
2. Enter the following menus: Powertrain / Engine and ECT / Data List / Coolant Temp.
3. Read the Coolant Temp value when the engine is cold and warmed up.
  Standard:
  
  ECT when the engine is cold: Same as ambient temperature
  
  ECT when the engine is warmed up: 75 to 95°C (167 to 203°F)
  
  NG: REPLACE ENGINE COOLANT TEMPERATURE SENSOR
  
  OK: Go to Next Step
READ VALUE OF TECHSTREAM (MAF)
1. Enter the following menus: Powertrain / Engine and ECT / Data List / MAF.
2. Allow the engine to idle until the ECT reaches 75°C (167°F).
3. Read the MAF value at idle rpm and 3000 rpm.
  Standard:
  
  MAF at idle rpm: 3 to 6 g/sec. (shift lever is in N position and A/C is OFF)
  
  MAF at 3000 rpm: 11 to 23 g/sec. (shift lever is in N position and A/C is OFF)
  
  NG: REPLACE MASS AIR FLOW METER
  
  OK: Go to Next Step
CHECK FUEL PRESSURE
1. Check the fuel pressure (see ON-VEHICLE INSPECTION ).
  NG: REPAIR OR REPLACE FUEL SYSTEM
  
  OK: Go to Next Step
CHECK FOR EXHAUST 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 malfunction, engine misfire may occur. The misfire counter can be read with the Techstream. Enter the following menus: Powertrain / Engine and ECT / Data List / Misfire / Cylinder #1 Misfire Count to #8.

NG: REPAIR OR REPLACE IGNITION SYSTEM

OK: Go to Next Step
INSPECT FUEL INJECTOR
HINT:

If the injectors are malfunctioning, engine misfire may occur. The misfire counter can be read with the Techstream. Enter the following menus: Powertrain / Engine and ECT / Data List / Misfire / Cylinder #1 Misfire Count to #8.

NG: REPLACE FUEL INJECTOR

OK: Go to Next Step

INSPECT HEATED OXYGEN SENSOR

Disconnect the H9 and H10 sensor connectors.

Measure the resistance of the heated oxygen sensor.

Standard resistance

TESTER CONNECTION SPECIFIED CONDITION CHART

Tester Connection	Specified Condition
1 (HT) - 2 (+B)	11 to 16 Ω
1 (HT) - 4 (E1)	10 kΩ or higher

NG: REPLACE HEATED OXYGEN SENSOR

Fig 1: Inspecting Heated Oxygen Sensor

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

OK: Go to Next Step

INSPECT EFI RELAY (Marking: EFI)

Remove the EFI relay from the engine room No. 2 relay block.

Measure the resistance of the EFI relay.

Standard resistance

TESTER CONNECTION SPECIFIED CONDITION CHART

Tester Connection	Specified Condition
3-5	10 kΩ or higher
3-5	Below 1 Ω (when battery voltage is applied to terminals 1 and 2)

Fig 2: EFI Relay Circuit Diagram

NG: REPLACE EFI RELAY

OK: Go to Next Step

CHECK WIRE HARNESS (HEATED OXYGEN SENSOR (SENSOR 1) - ECM)

Disconnect the H9 and H10 sensor connectors.
Disconnect the E2 and E4 ECM connectors.

Measure the resistance of the wire harness side connectors.

Standard resistance

TESTER CONNECTION SPECIFIED CONDITION CHART

Tester Connection	Specified Condition
H9-1 (HT) - E2-24 (HT1A)	Below 1 Ω
H9-3 (OX) - E2-30 (OX1A)	Below 1 Ω
H10-1 (HT) - E4-5 (HT2A)	Below 1 Ω
H10-3 (OX) - E4-28 (OX2A)	Below 1 Ω
H9-1 (HT) or E2-24 (HT1A) - Body ground	10 kΩ or higher
H9-3 (OX) or E2-30 (OX1A) - Body ground	10 kΩ or higher
H10-1 (HT) or E4-5 (HT2A) - Body ground	10 kΩ or higher
H10-3 (OX) or E4-28 (OX2A) - Body ground	10 kΩ or higher

NG: REPAIR OR REPLACE HARNESS AND CONNECTOR

Fig 3: Checking Wire Harness (Heated Oxygen Sensor (Sensor 1) - ECM)

OK: Go to Next Step

REPLACE HEATED OXYGEN SENSOR
PERFORM CONFIRMATION DRIVING PATTERN

Fig 4: Vehicle Speed Driving Pattern
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
1. Connect the Techstream to the DLC3.
2. Switch the tester from normal mode to check mode (see CHECK MODE PROCEDURE ).
3. Allow the engine to idle until the ECT reaches 75°C (167°F).
4. Allow the vehicle to run at 40 km/h (25 mph) or more for 25 seconds or more.
5. Allow the engine to idle for 30 seconds or more.
6. Perform steps (d) and (e) at least 3 times.
  HINT:
  
  If a malfunction exists, the MIL will be illuminated on the multi-information display.
  
  NOTE: If the conditions in this test are not strictly followed, you should perform steps (d) and (e).
  If you do not have the Techstream, turn the ignition switch OFF after performing steps (c) and (f), and then perform steps (c) and (f) again.
7. Allow the engine to idle for 30 seconds.
  NEXT: END