engine SUBARU LEGACY 1997 Service Repair Manual

H: DIAGNOSTICS PROCEDURE FOR ENGINE
HOOD SWITCH SIGNAL
1. Check engine hood switch input signal for
security control module.
Not OK
OK
Go to next step on basic diagnostics procedure.

2. Check engine hood switch.
OK
Not OK
Replace engine hood switch.
Repair or replace wiring harness between engine
hood switch and security control module.
B6M0451A
1. CHECK ENGINE HOOD SWITCH INPUT SIGNAL
FOR SECURITY CONTROL MODULE.
1) Remove security control module without disconnecting
connector.
2) Turn engine hood switch ON/OFF and measure voltage
between security control module connector and body.
Connector & terminal / Specified voltage:
(B93) No. 10—Body / 10 V, or more (Hood
closed)
/ 1 V, max. (Hood opened)
2. CHECK ENGINE HOOD SWITCH.
Refer to 6-2 [W22B3] for inspection of engine hood switch.


97
6-2DIAGNOSTICS
6. Security System

1. General
1. GENERAL DESCRIPTION

The on-board diagnostics (OBD) system detects and
indicates a fault in various inputs and outputs of the com-
plex electronic control. CHECK ENGINE malfunction indi-
cator lamp (MIL) in the combination meter indicates occur-
rence of a fault or trouble.

Further, against such a failure or sensors as may disable
the drive, the fail-safe function is provided to ensure the
minimal driveability.

The OBD system incorporated with the vehicles within
this engine family complies with Section 1968.1, California
Code of Regulations (OBD-II regulation). The OBD system
monitors the components and the system malfunction
listed in Engine Section which affects on emissions.

When the system decides that a malfunction occurs, MIL
illuminates. At the same time of the MIL illumination or
blinking, a diagnostic trouble code (DTC) and a freeze
frame engine conditions are stored into on-board com-
puter.

The OBD system stores freeze frame engine condition
data (engine load, engine coolant temperature, fuel trim,
engine speed and vehicle speed, etc.) into on-board com-
puter when it detects a malfunction first.

If the OBD system detects the various malfunctions
including the fault of fuel trim or misfire, the OBD system
first stores freeze frame engine conditions about the fuel
trim or misfire.

When the malfunction does not occur again for three
consecutive driving cycles, MIL is turned off, but DTC
remains at on-board computer.

The OBD-II system is capable of communication with a
general scan tool (OBD-II general scan tool) formed by ISO
9141 CARB.

The OBD-II diagnostics procedure is different from the
usual diagnostics procedure. When troubleshooting OBD-II
vehicles, connect Subaru select monitor or the OBD-II gen-
eral scan tool to the vehicle.
A: ENGINE
1. ENGINE AND EMISSION CONTROL SYSTEM

The Multipoint Fuel Injection (MFI) system is a system
that supplies the optimum air-fuel mixture to the engine for
all the various operating conditions through the use of the
latest electronic technology.
With this system fuel, which is pressurized at a constant
pressure, is injected into the intake air passage of the cyl-
inder head. The injection quantity of fuel is controlled by an
intermittent injection system where the electro-magnetic
injection valve (fuel injector) opens only for a short period
of time, depending on the quantity of air required for one
cycle of operation. In actual operation, the injection quan-
2
2-7ON-BOARD DIAGNOSTICS II SYSTEM
1. General

tity is determined by the duration of an electric pulse
applied to the fuel injector and this permits simple, yet
highly precise metering of the fuel.

Further, all the operating conditions of the engine are
converted into electric signals, and this results in additional
features of the system, such as large improved
adaptability, easier addition of compensating element, etc.
The MFI system also has the following features:
1) Reduced emission of harmful exhaust gases.
2) Reduced in fuel consumption.
3) Increased engine output.
4) Superior acceleration and deceleration.
5) Superior startability and warm-up performance in cold
weather since compensation is made for coolant and
intake air temperature.
3
2-7ON-BOARD DIAGNOSTICS II SYSTEM
1. General

1Engine control module (ECM)

2Ignition coil

3Ignitor

4Crankshaft position sensor

5Camshaft position sensor

6Throttle position sensor

7Fuel injectors

8Pressure regulator

9Engine coolant temperature sensor

10Mass air flow sensor

11Idle air control solenoid valve

12Purge control solenoid valve

13Fuel pump

14PCV valve

15Air cleaner

16Canister

17Main relay

18Fuel pump relay

19Fuel filter

20Front catalytic converter

21Rear catalytic converter

22EGR valve (AT vehicles only)

23EGR control solenoid valve (AT vehicles only)

24Radiator fan
25Radiator fan relay

26Pressure sources switching solenoid valve

27Knock sensor

28Back-pressure transducer (AT vehicles only)

29Front oxygen sensor

30Rear oxygen sensor (2200 cc Federal spec. vehicles)

31Pressure sensor

32A/C compressor

33Inhibitor switch

34CHECK ENGINE malfunction indicator lamp (MIL)

35Tachometer

36A/C relay

37A/C control module

38Ignition switch

39Transmission control module (TCM) (AT vehicles only)

40ABS/TCS control module (TCS equipped models)

41Vehicle speed sensor

42Data link connector (For Subaru select monitor)

43Data link connector (For Subaru select monitor and OBD-II
general scan tool)

44Two way valve

45Rear oxygen sensor (2200 cc California spec. vehicles)

46Filter
5
2-7ON-BOARD DIAGNOSTICS II SYSTEM
1. General

1Engine control module (ECM)

2Ignition coil

3Ignitor

4Crankshaft position sensor

5Camshaft position sensor

6Throttle position sensor

7Fuel injectors

8Pressure regulator

9Engine coolant temperature sensor

10Mass air flow sensor

11Idle air control solenoid valve

12Purge control solenoid valve

13Fuel pump

14PCV valve

15Air cleaner

16Canister

17Main relay

18Fuel pump relay

19Fuel filter

20Front catalytic converter

21Rear catalytic converter

22EGR valve (AT vehicles only)

23EGR control solenoid valve (AT vehicles only)

24Radiator fan

25Radiator fan relay

26Pressure sources switching solenoid valve
27Front oxygen sensor

28Rear oxygen sensor (2200 cc Federal spec. vehicles)

29Pressure sensor

30A/C compressor (With A/C models)

31Inhibitor switch

32CHECK ENGINE malfunction indicator lamp (MIL)

33Tachometer

34A/C relay (With A/C models)

35A/C control module (With A/C models)

36Ignition switch

37Transmission control module (TCM)

38Vehicle speed sensor

39Data link connector (For Subaru select monitor)

40Data link connector (For Subaru select monitor and OBD-II
general scan tool)

41Rear oxygen sensor (2200 cc California spec. vehicles)

42Knock sensor

43Back-pressure transducer (AT vehicles only)

44Filter

45Fuel tank pressure sensor

46Pressure control solenoid valve

47Fuel temperature sensor

48Fuel level sensor

49Vent control solenoid valve

50Air filter
7
2-7ON-BOARD DIAGNOSTICS II SYSTEM
1. General

1Engine control module (ECM)

2Ignition coil

3Ignitor

4Crankshaft position sensor

5Camshaft position sensor

6Throttle position sensor

7Fuel injectors

8Pressure regulator

9Engine coolant temperature sensor

10Mass air flow sensor

11Idle air control solenoid valve

12Purge control solenoid valve

13Fuel pump

14PCV valve

15Air cleaner

16Canister

17Main relay

18Fuel pump relay

19Fuel filter

20Front catalytic converter

21Rear catalytic converter

22EGR valve
23EGR control solenoid valve

24Radiator fan

25Radiator fan relay

26Pressure sources switching solenoid valve

27Knock sensor

28Back-pressure transducer

29Front oxygen sensor

30Rear oxygen sensor

31Pressure sensor

32A/C compressor

33Inhibitor switch

34CHECK ENGINE malfunction indicator lamp (MIL)

35Tachometer

36A/C relay

37A/C control module

38Ignition switch

39Transmission control module (TCM)

40Vehicle speed sensor

41Data link connector (Subaru select monitor)

42Data link connector (OBD-II general scan tool)

43Two way valve

44Filter
9
2-7ON-BOARD DIAGNOSTICS II SYSTEM
1. General

2. Electrical Components Location
A: ENGINE
1. MODULE
OBD0003E
B2M0430H
1Engine control module (ECM)

2Data link connector (for Subaru select monitor only)

3Data link connector (for Subaru select monitor and OBD-II
general scan tool)
4Test mode connector

5CHECK ENGINE malfunction indicator lamp (MIL)
12
2-7ON-BOARD DIAGNOSTICS II SYSTEM
2. Electrical Components Location

2. SENSOR
B2M1169D
1Pressure sensor

2Mass air flow sensor

3Engine coolant temperature sensor

4Throttle position sensor
5Knock sensor

6Camshaft position sensor

7Crankshaft position sensor
14
2-7ON-BOARD DIAGNOSTICS II SYSTEM
2. Electrical Components Location

B2M0470C
3. Diagnosis System
A: CHECK ENGINE MALFUNCTION
INDICATOR LAMP (MIL)
1. ACTIVATION OF CHECK ENGINE MALFUNCTION
INDICATOR LAMP (MIL)
1) When ignition switch is turned to ON (engine off), the
CHECK ENGINE malfunction indicator lamp (MIL) in the
combination meter illuminates.
NOTE:
If the MIL does not illuminate, perform diagnostics of the
CHECK ENGINE light circuit or the combination meter cir-
cuit.
OBD0053A
2) After starting the engine, the MIL goes out. If it does not,
either the engine or the emission control system is mal-
functioning.
OBD0054A
3) If the diagnosis system senses a misfire which could
damage the catalyzer, the MIL will blink at a cycle of 1 Hz.
OBD0055A
4) When ignition switch is turned to ON (engine off) or to
“START” with the test mode connector connected, the MIL
blinks at a cycle of 3 Hz.
31
2-7ON-BOARD DIAGNOSTICS II SYSTEM
3. Diagnosis System

3. CURRENT POWERTRAIN DIAGNOSTIC DATA
(MODE $01)
Refers to data denoting the current operating condition of
analog input/output, digital input/output and/or the power-
train system.
A list of the support data and PID (Parameter Identification)
codes are shown in the following table.
PID DataUnit of measure
01 Number of emission-related powertrain trouble codes and MIL status ON/OFF
03 Fuel system control status—
04 Calculated engine load value%
05 Engine coolant temperature°C
06 Short term fuel trim%
07 Long term fuel trim%
0B Intake manifold absolute pressurekPa
0C Engine revolutionrpm
0D Vehicle speedkm/h
0E Ignition timing advance°
10 Air flow rate from mass air flow sensor g/sec
11 Throttle valve opening angle%
13 Check whether oxygen sensor is installed.—
14 Oxygen sensor output voltage and short term fuel trim associated with oxygen sensor—bank 1 V and %
15 Oxygen sensor output voltage and short term fuel trim associated with oxygen sensor—bank 2 V and %
1C On-board diagnosis system—
NOTE:
Refer to OBD-II general scan tool manufacturer’s instruc-
tion manual to access generic OBD-II PIDs (MODE $01).
33
2-7ON-BOARD DIAGNOSTICS II SYSTEM
3. Diagnosis System