Oxygen sensor heater circuit testing

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^ Check oxygen sensor heater circuit at harness side of oxygen sensor connector (inset).

• Attach digital multimeter set on volts to harness terminals 2 and 3.

If voltage signal does not fluctuate or if there is no change when oil filler cap is removed, check for a faulty sensor wire in harness or connector (arrow) in engine compartment. If no wiring faults can be found, sensor is probably faulty and should be replaced.

Oxygen sensor replacement is a maintenance procedure scheduled at a specified time or mileage interval set by Porsche. See 030 Maintenance.

Oxygen sensor electrical circuit

Luggage compartment I to fuel pump fusebox 1 ,

Battery

Main/ fuel pump relay )

Main/ fuel pump relay )

0.75 8KA/VT

DME control module (ECM)

0.75 8KA/VT

29 fuel pump relay switch shield 23

d from ignition switch

Oxygen sensor from ignition switch

WIRING COLOR CODE

bk

black

br

brown

rd

red

yl

yellow

gn

green

bu

blue

vi

violet

gy

grey

wt

white

pk

10.75 BR

0018412

With engine running there should be battery voltage (12 volts) to sensor heater.

• If not, check output at terminal 87b of main/fuel pump relay.

• Check oxygen sensor harness ground wire for continuity to ground.

Wire colors leading to the sensor plug are different from wire colors leading to the sensor itself.

Table k. Oxygen Sensor Wire Colors

Function

Harness

Sensor

Signal

Green

Black

Heater

Yellow

White

Ground

Brown

White

911 Suppress Sensor Procedure

COMPONENT REPLACEMENT Main/fuel pump relay, replacing

— Remove driver seat as described in 720 Seats. "A Detach wiring harness to main relay (arrow).

— Remove one M6 mounting nut and remove relay.

— Installation is reverse of removal.

Volume air flow sensor, replacing

^ Loosen large hose clamp (A) holding intake rubber boot to volume air flow sensor.

— Disconnect wiring harness (B) from air flow sensor.

— Remove mounting bolt (C) from air flow sensor body.

0013766

Wiring Harness 1984 720
0019767
1984 Porsche 911 Mirror Wiring

Unclip (arrows) air filter housing cover. Remove air filter cover and element.

^ Remove air flow sensor mounting bolts (arrows) from inside air filter housing.

— Slide volume air flow sensor out.

— Installation is reverse of removal.

Tightening Torques

• Volume air flow sensor to intake manifold 8 Nm (6 ft-lb)

• Air filter housing to air flow sensor 8 Nm (6 ft-lb)

Cylinder head temperature sensor, replacing

— Raise car and support in a safe manner.

Make sure the car is stable and well supported at all times. Use a professional automotive lift or jack stands designed for the purpose. A floor jack is not adequate support.

Cylinder Head Heater Well

Pull out connector locking plate at sensor connectors in left front of engine compartment.

• Disconnect cylinder head temperature sensor connector (white connector).

— Working underneath engine remove rubber grommet at left rear (flywheel end) engine shroud.

Allow the engine to cool fully before working near the exhaust system or at the cylinder heads.

Porsche Temp Sensor Socket

Using Porsche special tool 9222 or equivalent (a deep socket with a slit cut in the side), remove temperature sensor (arrow) from cylinder head 3.

— Pull wire with temperature sensor attached through rubber grommet opening.

— Installation is reverse of removal. NOTE —

Before installing, apply a light coat of Molykote® HTP to the threads.

Tightening Torque

• Cylinder head temperature sensor to cylinder head 15 Nm (11 ft-lb)

Jenvey Throttle Bodies For Porsche 911

^ Remove switch mounting screws (arrows).

— Pull switch off side of throttle body.

— Installation is reverse of removal.

Idle position switch

0018762

Full throttle switch, replacing

The full throttle and the idle switch are both attached to the throttle housing.

^ Disconnect throttle switch wiring harness connector from throttle switch.

Idle speed control valve, replacing

^ Remove two hoses (A) and electrical harness connector from valve (C). Remove mounting nuts (B).

— Remove idle air control valve.

— Installation is reverse of removal.

^ Remove switch mounting screws (arrows).

— Pull switch off side of throttle body.

— Installation is reverse of removal.

After replacing idle switch, check idle switch adjustment as described earlier in Full throttle switch, testing and adjusting.

Idle position switch

0018762

Porsche 944 Test Connector

0018763

Oxygen Sensors Heaters Ready

Fuel injectors, replacing

1984 Porsche 911 Mirror Wiring

Always use new injector sealing kits when servicing injectors.

Left side injectors, replacing

Remove large plastic elbow tube between heater blower fan on top of engine and heat exchanger feed tube.

• Remove bolts holding tube to blower housing, in front and at rear of blower housing (arrows).

• Loosen hose clamp at heat exchanger end (bottom of elbow) and slide elbow out.

Remove left fuel rail and injectors: • Disconnect left fuel rail supply and return lines (A).

Have a shop towel ready to soak up spilled fuel.

■ Cut wire ties and disconnect injector harness connectors 1, 2 and 3 (B).

• Remove fuel rail mounting bolts (C) from intake runners 1 and 3.

»Carefully pull up on fuel rail and remove with injectors.

^ To remove an injector:

• Remove locking clip holding injector to fuel rail (1).

— Installation is reverse of removal. Tightening Torque

Gasoline is highly flammable and its vapors are explosive. Do not smoke or work on a car near heaters or other fire hazards when diagnosing and repairing fuel system problems. Have a fire extinguisher available in case of an emergency.

0018767

Right side injectors, replacing

Unclip (arrows) air filter housing cover. Remove air filter cover and element.

^ Remove right fuel rail and injectors:

• Disconnect both fuel lines, one at rear of fuel rail, one at front (A).

Have a shop towel ready to soak up spilled fuel.

• Cut wire ties and disconnect injector harness connectors 4, 5 and 6 (B).

• Remove fuel rail mounting bolts (C) from intake runners 4 and 6.

• Carefully pull up on injector rail and remove with injectors.

— Remove locking clips holding injectors to fuel rail and remove injectors from rail.

— Installation is reverse of removal.

Tightening Torque

Fuel pressure regulator, replacing

The fuel pressure regulator is located at the rear (flywheel end) left of the engine, at the end of the left fuel rail.

Gasoline is highly flammable and its vapors are explosive. Do not smoke or work on a car near heaters or other fire hazards when diagnosing and repairing fuel system problems. Have a fire extinguisher available in case of an emergency.

1984 Svo Fuel Pressure Dampner

[0018773

Oxygen Sensors Heaters Ready

,0018774

^ Remove fuel pressure regulator vacuum line (A). • Remove both fuel lines (B).

Have shop towels ready to soak up fuel.

• Loosen fuel line clamp (C) at bottom of regulator and remove line.

• Remove 24 mm nut (D) at base of regulator housing and remove regulator.

— Installation is reverse of removal.

1984 Porshe Wiring Diagram

Have shop towels ready to soak up fuel.

Fuel pressure damper, replacing

— The fuel pressure damper is located at the rear (flywheel end) right of the engine, at the end of the right fuel rail.

^ Remove fuel pressure damper vacuum line (A). • Remove both fuel lines (B).

• Remove M6 mounting bolt (C) and remove regulator. — Installation is reverse of removal.

FUEL SYSTEM ELECTRICAL CIRCUITS

The electrical information and schematics provided here can be used as guide in diagnosing fuel system electrical problems.

The entire electrical system of the car is covered in 970 Electrical Wiring Diagrams and 971 Electrical Component Locations.

Ground locations

Tight and corrosion free ground connections, including the negative terminal of the battery and the ground straps, are essential to trouble-free operation.

Ground locations for the DME engine management system are shown in Table I.

^ Battery ground location G104 (arrow).

Engine-body-transmission ground strap G302 (arrow).

Porsche 911 Dme Relay Diagram

0018781

Strap For 911 Window Washer

0018776

1984 928 Porsche Fuel Filter

0018775

^ Left rear engine compartment ground location G402 (arrow) in front of fuel filter. (Fuel filter removed for photo.)

0018775

Intake runner 1 ground location G407 (arrow).

Table I. DME System Ground Locations

Ground

Location

Connections

G104

In left front of luggage compartment

Battery ground Oil cooler fan

Windshield washer system Headlight washer system Dual horns

G302

Engine-body-transmission ground strap

Engine Body

Transmission

G402

In left rear of engine compartment

Rear window wiper motor Rear window defogger Heater system Oil tank level sender

G407

On intake runner 1

Throttle valve switch

Wiring schematics

The schematic diagrams on the following pages cover the DME fuel injection electrical system. DME ignition system wiring is shown in 280 Ignition System.

The DME wiring diagrams shown are based on model year 1987. Wiring colors may vary slightly for other model year vehicles.

DME fuel injection (page 1)

from A/C compressor (electromagentic clutch)

to test connector (terminal A)

DME control module rs

Ignition coil (terminal 1)

i timing control from

Instrument cluster (battery voltage in start)

A/C on input engine temperature input

10 17 16 19 13

grounds closed throttle 2

engine speed output 11

lull throttle 3

Altitude correction 28

Throttle switch

JL

71

NTC

/

Engine temperature sensor

Engine temperature sensor

Ground

(On no. 1 intake runner)

(On no. 1 intake runner)

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