1996 SUBARU LEGACY sensor

OBD0142
B: DTC P0100
—MASS AIR FLOW SENSOR CIRCUIT
MALFUNCTION (QA)—
DTC DETECTING CONDITION:

Immediately at fault recognition
TROUBLE SYMPTOM:

Erroneous idling

Engine stalls.

Poor driving performance
10B1Connect Subaru Select Monitor or the OBD-II
general scan tool, and read data.10B5Check harness between ECM and mass air
flow sensor connector.
10B2Check input signal for ECM. (Using voltage
meter and Subaru Select Monitor.)
10B3Check power supply to mass air flow sensor.
10B4Check harness between ECM and mass air
flow sensor connector.
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES.




125
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

OBD0145A
10B1CONNECT SUBARU SELECT MONITOR
OR THE OBD-II GENERAL SCAN TOOL,
AND READ DATA.
1) Turn ignition switch to OFF.
2) Connect Subaru Select Monitor or the OBD-II general
scan tool to data link connector.
3) Turn ignition switch to ON and Subaru Select Monitor or
the OBD-II general scan tool switch to ON.
4) Start engine.
B2M0481
5) Read data on Subaru Select Monitor or OBD-II general
scan tool.

Subaru Select Monitor
Designate mode using function key.
Function mode: F06

F06: Mass air flow and voltage input from mass air flow
sensor are shown on display at the same time.
: Is the value equal to or more than 1.3 g/sec
or 0.3 V and equal to or less than 250 g/sec
or 5.0 V in function mode F06?
Probable cause: Poor connect of connectors, circuit and
grounding line.
: Even if MIL lights up, the circuit has returned to a
normal condition at this time. A temporary poor
contact of the connector or harness may be the
cause. Repair harness or connector in the mass
air flow sensor.
NOTE:
In this case, repair the following:

Open or short circuit in harness between mass air flow
sensor and ECM connector

Poor contact in mass air flow sensor or ECM connector
: Go to next.
B2M0481
: Is the value less than 1.3 g/sec or 0.3 V in
function mode F06?
: Go to step10B2.
: Go to step10B5.

OBD-II general scan tool
For detailed operation procedures, refer to the OBD-II Gen-
eral Scan Tool Instruction Manual.
128
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

B2M0532A
10B2CHECK INPUT SIGNAL FOR ECM.
(USING VOLTAGE METER AND SUBARU
SELECT MONITOR.)
Measure voltage between ECM connector and chassis
ground while engine is idling.
: Connector & terminal
(B84) No. 5 (+)—Chassis ground ():
Is the voltage less than 0.3 V?
: Go to step10B3.
: Go to next.
B2M0481
: Does the voltage change more than 0.3 V by
shaking harness and connector of ECM
while monitoring the value with Subaru
select monitor?
: Repair poor contact in ECM connector.
: Replace ECM.
B2M0645A
10B3CHECK POWER SUPPLY TO MASS AIR
FLOW SENSOR.
1) Turn ignition switch to OFF.
2) Disconnect connector from mass air flow sensor.
3) Turn ignition switch to ON.
4) Measure voltage between mass air flow sensor connec-
tor and engine ground.
: Connector & terminal
(B3) No. 1 (+)—Engine ground ():
Is the voltage more than 10 V?
: Go to step10B4.
: Repair open circuit in harness between main relay
and mass air flow sensor connector.
129
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

B2M0533A
10B4CHECK HARNESS BETWEEN ECM AND
MASS AIR FLOW SENSOR CONNECTOR.
1) Turn ignition switch to OFF.
2) Disconnect connector from ECM.
3) Measure resistance of harness between ECM and
mass air flow sensor connector.
: Connector & terminal
(B84) No. 5—(B3) No. 4:
Is the resistance less than 1Ω?
: Go to next.
: Repair harness and connector.
NOTE:
In this case, repair the following:

Open circuit in harness between ECM and mass air flow
sensor connector

Poor contact in mass air flow sensor connector

Poor contact in ECM connector
: Connector & terminal
(B84) No. 18—(B3) No. 3:
Is the resistance less than 1Ω?
: Go to next.
: Repair harness and connector.
NOTE:
In this case, repair the following:

Open circuit in harness between ECM and mass air flow
sensor connector

Poor contact in mass air flow sensor connector

Poor contact in ECM connector
: Connector & terminal
(B84) No. 20—(B3) No. 2:
Is the resistance less than 1Ω?
: Replace mass air flow sensor.
: Repair harness and connector.
NOTE:
In this case, repair the following:

Open circuit in harness between ECM and mass air flow
sensor connector

Poor contact in mass air flow sensor connector

Poor contact in ECM connector
130
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

B2M0481
10B5CHECK HARNESS BETWEEN ECM AND
MASS AIR FLOW SENSOR CONNECTOR.
1) Turn ignition switch to OFF and Subaru Select Monitor
or the OBD-II general scan tool switch to OFF.
2) Disconnect connector from mass air flow sensor.
3) Turn ignition switch to ON and Subaru Select Monitor or
the OBD-II general scan tool switch to ON.
4) Read data on Subaru select monitor or OBD-II general
scan tool.

Subaru Select Monitor
Designate mode using function key.
Function mode: F06
: Is the value more than 250 g/sec or5Vin
function mode F06?
: Repair short circuit in harness between mass air
flow sensor and ECM connector.
: Go to next.
: Is there poor contact in mass air flow sensor
connector?
: Repair poor contact in mass air flow sensor con-
nector.
: Replace mass air flow sensor.

OBD-II general scan tool
For detailed operation procedures, refer to OBD-II General
Scan Tool Instruction Manual.
131
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

OBD0152
C: DTC P0101
—MASS AIR FLOW SENSOR CIRCUIT
RANGE/PERFORMANCE PROBLEM
(QA
—R)—
DTC DETECTING CONDITION:

Two consecutive trips with fault
TROUBLE SYMPTOM:

Erroneous idling

Engine stalls.

Poor driving performance
10C1Check DTC P0100 on display.
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES.

WIRING DIAGRAM:

LHD Model
B2M0531
132
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

WIRING DIAGRAM:

RHD Model
B2M0785
10C1
CHECK DTC P0100 ON DISPLAY.
: Does the Subaru select monitor or OBD-II
general scan tool indicate DTC P0100?
: Inspect DTC P0100 using“10. Diagnostics Chart
with Trouble Code 2-7 [T1000]”.
NOTE:
In this case, it is not necessary to inspect DTC P0101.
: Replace mass air flow sensor.
133
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code

OBD0154
D: DTC P0105
—PRESSURE SENSOR CIRCUIT
MALFUNCTION (P
—S)—
DTC DETECTING CONDITION:

Immediately at fault recognition
10D1Connect Subaru Select Monitor or the OBD-II
general scan tool, and read data.

10D2Check input signal for ECM. (Using voltage
meter and Subaru Select Monitor.)
10D3Check harness between ECM and pressure
sensor connector.
10D4Check harness between ECM and pressure
sensor connector.
CAUTION:
After repair or replacement of faulty parts, conduct
CLEAR MEMORY and INSPECTION MODES.



134
2-7ON-BOARD DIAGNOSTICS II SYSTEM
10. Diagnostics Chart with Trouble Code