Subaru Impreza 3 / Impreza WRX / Impreza WRX STI. Manual — part 132

FU(w/o STI)-55

Rear Oxygen Sensor

FUEL INJECTION (FUEL SYSTEMS)

17.Rear Oxygen Sensor

A: REMOVAL

1) Disconnect the ground cable from battery.

2) Lift up the vehicle.

3) Disconnect the connector from the rear oxygen

sensor, and remove the clip (A) holding the rear ox-

ygen sensor harness.

4) Apply spray-type lubricant to the threaded por-

tion of rear oxygen sensor, and leave it for one

minute or more.

5) Remove the rear oxygen sensor.
CAUTION:

When removing the rear oxygen sensor, wait

until exhaust pipe cools, otherwise it will dam-

age the exhaust pipe.

B: INSTALLATION

CAUTION:

If lubricant is spilt onto the exhaust pipe, wipe it

off completely with cloth to avoid emission of

smoke or causing a fire.

1) Before installing rear oxygen sensor, apply the

anti-seize compound only to the threaded portion of

rear oxygen sensor to make the next removal eas-

ier.
CAUTION:

Never apply anti-seize compound to the protec-

tor of rear oxygen sensor.
Anti-seize compound:

NEVER-SEEZ NSN, JET LUBE SS-30 or

equivalent

2) Install the rear oxygen sensor.
Tightening torque:

21 N·m (2.1 kgf-m, 15.5 ft-lb)

3) Connect the connector to the rear oxygen sen-

sor, and hold the rear oxygen sensor harness with

the clip (A).

4) Lower the vehicle.

IN-00203

FU-04637

(A)

FU-04626

FU-04626

FU-04637

(A)

FU(w/o STI)-56

Rear Oxygen Sensor

FUEL INJECTION (FUEL SYSTEMS)

5) Connect the battery ground terminal.

C: INSPECTION

1) Check that the rear oxygen sensor has no defor-

mation, cracks or other damages.

2) Measure the resistance between rear oxygen

sensor terminals.

Terminal No.

Standard

1 and 2

5.6

+0.8

–0.6

Ω

(when 20°C (68°F))

IN-00203

2 1
4 3

FU-04073

FU(w/o STI)-57

Engine Control Module (ECM)

FUEL INJECTION (FUEL SYSTEMS)

18.Engine Control Module (ECM)

A: REMOVAL

1) Disconnect the ground cable from battery.

2) Remove the lower inner trim of passenger’s

side. <Ref. to EI-57, REMOVAL, Lower Inner

Trim.>

3) Turn over the floor mat of passenger’s seat.

4) Remove the protect cover.

5) Remove the nuts and bolts which hold the ECM

to the bracket.

6) Disconnect the ECM connectors, and take out

the ECM.

B: INSTALLATION

Install in the reverse order of removal.
CAUTION:

• When the ECM of model with immobilizer has

been replaced, be sure to perform the registra-

tion of immobilizer system. (Refer to “PC appli-

cation help for Subaru Select Monitor”.)

• If replacing ECM or the bracket, replace both

parts with new parts at a time.

• After installing the bracket to ECM, do not

separate the bracket.

• If the bracket has been installed to ECM in the

wrong direction, replace both parts to new

parts.
NOTE:

When replacing the ECM, be careful not to use the

wrong spec. ECM to avoid any damage on the fuel

injection system.
Tightening torque:

7.5 N·m (0.8 kgf-m, 5.5 ft-lb)

C: INSPECTION

Check that the ECM has no deformation, cracks or

other damages.

IN-00203

FU-03416

FU-03417

FU(w/o STI)-58

Main Relay

FUEL INJECTION (FUEL SYSTEMS)

19.Main Relay

A: REMOVAL

1) Disconnect the ground cable from battery.

2) Remove the main relay from the relay block on

the back side of the glove box.

B: INSTALLATION

Install in the reverse order of removal.

C: INSPECTION

1) Check that the main relay has no deformation,

cracks or other damages.

2) Measure the resistance between main relay ter-

minals.

IN-00203

FU-03418

Terminal No.

Standard

1 and 2

1 MΩ or more

3 and 4

130.4 — 230.8 Ω

(when 20°C (68°F))

1
2

3 4

(1)

(2)

(1)

(4)

(2)

(3)

(3)

(4)

IN-02836