Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Service manual — part 32

FU(STI)-40

Knock Sensor

FUEL INJECTION (FUEL SYSTEMS)

7. Knock Sensor

A: REMOVAL

1) Disconnect the ground cable from battery.

2) Remove the intercooler. <Ref. to IN(STI)-12,

REMOVAL, Intercooler.>

3) Remove the intake manifold. <Ref. to FU(STI)-

17, REMOVAL, Intake Manifold.>

4) Remove the secondary air combination valve

RH. <Ref. to EC(STI)-29, REMOVAL, Secondary

Air Combination Valve.>

5) Remove the knock sensor from cylinder block.

B: INSTALLATION

1) Install the knock sensor to the cylinder block.
NOTE:

The portion of the knock sensor cord that is pulled

out must be positioned at a 60° angle relative to the

engine rear.
Tightening torque:

24 N·m (2.4 kgf-m, 17.7 ft-lb)

2) Install the secondary air combination valve RH.

<Ref. to EC(STI)-30, SECONDARY AIR COMBI-

NATION VALVE RH, INSTALLATION, Secondary

Air Combination Valve.>

3) Install the intake manifold. <Ref. to FU(STI)-21,

INSTALLATION, Intake Manifold.>

4) Install the intercooler. <Ref. to IN(STI)-13, IN-

STALLATION, Intercooler.>

5) Connect the battery ground terminal.

C: INSPECTION

1) Check that the knock sensor has no deforma-

tion, cracks or other damages.

2) Measure the resistance between knock sensor

terminals.

(A) Front side of vehicle

IN-00203

FU-04494

FU-05758

60

(A)

Terminal No.

Standard

1 and 2

560±28 kΩ

IN-00203

2 1

EC-02428

FU(STI)-41

Throttle Position Sensor

FUEL INJECTION (FUEL SYSTEMS)

8. Throttle Position Sensor

A: SPECIFICATION

Throttle body is a non-disassembled part, so do not

remove the throttle position sensor from throttle

body.

Refer to “Throttle Body” for removal and installation

procedure. <Ref. to FU(STI)-15, REMOVAL, Throt-

tle Body.> <Ref. to FU(STI)-15, INSTALLATION,

Throttle Body.>

FU(STI)-42

Mass Air Flow and Intake Air Temperature Sensor

FUEL INJECTION (FUEL SYSTEMS)

9. Mass Air Flow and Intake Air

Temperature Sensor

A: REMOVAL

1) Disconnect the ground cable from battery.

2) Disconnect the connector (A) from the mass air

flow and intake air temperature sensor, and re-

move the mass air flow and intake air temperature

sensor.

B: INSTALLATION

Install in the reverse order of removal.
Tightening torque:

1 N·m (0.1 kgf-m, 0.7 ft-lb)

C: INSPECTION

1. CHECK THE MASS AIR FLOW SENSOR

UNIT

1) Connect the battery positive terminal to terminal

No. 3 and the battery ground terminal to terminal

No. 4, the circuit tester positive terminal to terminal

No. 5 and the circuit tester ground terminal to termi-

nal No. 4.

2) Check the voltage changes when air is blown to

the mass air flow sensor unit in arrow direction.

2. CHECK THE INTAKE AIR TEMPERA-

TURE SENSOR UNIT

Measure the resistance between intake air temper-

ature sensor terminals.

3. OTHER INSPECTIONS

1) Check that the mass air flow and intake air tem-

perature sensor has no deformation, cracks or oth-

er damages.

2) Check that the mass air flow and intake air tem-

perature sensor has no dirt.

IN-00203

FU-05798

(A)

5 4 3 2 1

FU-04062

V

Temperature

Terminal No.

Standard

–20°C (–4°F)

1 and 2

16.0±2.4 kΩ

20°C (68°F)

2.45±0.24 kΩ

60°C (140°F)

0.580±0.087 kΩ

FU-04063

FU-04064

5 4 3 2 1

FU(STI)-43

Manifold Absolute Pressure Sensor

FUEL INJECTION (FUEL SYSTEMS)

10.Manifold Absolute Pressure

Sensor

A: REMOVAL

1) Disconnect the ground cable from battery.

2) Disconnect the connector (A) from the manifold

absolute pressure sensor, and remove the mani-

fold absolute pressure sensor from throttle body.

B: INSTALLATION

Install in the reverse order of removal.
NOTE:

Use new O-rings.
Tightening torque:

2 N·m (0.2 kgf-m, 1.5 ft-lb)

C: INSPECTION

1) Check that the manifold absolute pressure sen-

sor has no deformation, cracks or other damages.

2) Connect dry-cell battery positive terminal to ter-

minal No. 3 and dry-cell battery ground terminal to

terminal No. 2, circuit tester positive terminal to ter-

minal No. 1 and the circuit tester negative terminal

to terminal No. 2.
NOTE:

• Use new dry-cell batteries.

• Using circuit tester, check the voltage of a single

dry-cell battery is 1.6 V or more. And also check the

voltage of three batteries in series is between 4.8 V

and 5.2 V.

3) Check the voltage at a normal atmospheric pres-

sure.
NOTE:

The atmospheric pressure at higher altitude is low-

er than normal. Therefore, the voltage is lower than

the standard value.

IN-00203

FU-05799

(A)

Terminal No.

Standard

1 (+) and 2 (–)

Approx. 2.0 V

(when 25°C (77°F))

FU-04491

V

3 2 1

1.5V

1.5V

1.5V

4.8 5.2V