Page 417 of 4770

Check each circuit found to be a possible cause of trouble according to the results of the check in
or . The numbers in the table below show the order in which the checks should be performed.Check for open and short in harness and connector between engine control module and
main oxygen sensor, engine control module and data link connector 1 (See page
IN±31).
Does malfunction disappear when a good main oxygen sensor is
installed?Check each item found to be a possible cause of problem.
Check compression (See page EG1±23).
Repair or replace harness or connector.
Check and replace engine control module.
Characteristics deviation in
manifold absolute pressure sensor.
Characteristics deviation
in engine coolant temp. sensor.
Replace main oxygen sensor.
*: Except California specification vehicles.Characteristics deviation
in intake air temp. sensor. Main oxygen sensor
signal continue at OV.
Repair or replace.
Repair or replace.
Faulty sensor installation.Possible Cause
Injector circuit
Valve timing
Fuel system Air leakageSee page
IG±6, 26*
YES
EG1±410
EG1±360 EG1±419
EG1±372 EG1±173
EG1±356 Misfire
EG1±36
± 5S±FE ENGINECIRCUIT INSPECTIONEG1±367
Page 418 of 4770
Check each circuit found to be a possible cause of trouble according to the results of the check in
.The numbers in the table below show the order in which the checks should be performed.
Does malfunction disappear when a good main oxygen sensor is
installed? Check each item found to be a possible cause of problem.
Check compression (See page EG1±23).
Check and replace engine control module.
Characteristics deviation
in engine coolant temp. sensor.
Characteristics deviation in
manifold absolute pressure sensor.
Replace main oxygen sensor.
Main oxygen sensor
signal continue at 5.0 V.
x: Except California specification vehicles.Characteristics deviation
in intake air temp. sensor. Main oxygen sensor
signal is normal.
Repair or replace.
Repair or replace.
Possible Cause
Injector circuit
Valve timing
Fuel system Air leakageSee page
IG±6, 26*
YES
EG1±410
EG1±360 EG1±419
EG1±372 EG1±173
EG1±356 Misfire
EG1±36
± 5S±FE ENGINECIRCUIT INSPECTIONEG1±368
Page 419 of 4770
CIRCUIT DESCRIPTION
The sub oxygen sensor is installed on the exhaust pipe. Its construction and operation is the same as
the main oxygen sensor on page EG1±352.
Main oxygen sensor signal is 0.45 V or more
and sub oxygen sensor signal is 0.45 V or less
under conditions (a) and (b).
(2 trip detection logic) *
(a) Engine coolant temp. : 80C (1 76F) or more.
(b) Accel. pedal : Fully depressed for 2 sec. or more.wOpen or short in sub oxygen sensor circuit.
wSub oxygen sensor
wECM Diagnostic Trouble Code Detecting Condition
* : See page EG1±307.
Trouble Area
DTC 27 Sub Oxygen Sensor Circuit
DTC No.
± 5S±FE ENGINECIRCUIT INSPECTIONEG1±369
Page 420 of 4770

Disconnect the E F I fuse (15 A) for 10 sec. or more, with IG switch OFF.
Initiate test mode (Connect terminals TE2 and E1 of data link connector 1 or 2
with I G switch OFF).
Start the engine and warm up, with all ACC switch OFF.
After the engine is warmed up, let it drive at 50 ~ 55 mph (80 ~ 88 km/h)
for 10 min. or more.
After driving, stop at a safe place and perform idling for 2 min. or less.
After performing the idling in (4) , perform acceleration to 60 mph (96 km/h)
with the throttle valve fully open.
HINT: If a malfunction exists, the malfunction indicator lamp will light up during
step.
NOTICE: If the conditions in this test are not strictly followed, detection of the
malfunction will not be possible.
CIRCUIT DESCRIPTION (Cont'd)
DIAGNOSIS TROUBLE CODE DETECTION DRIVING PATTERN
Purpose of the driving pattern.
(a) To simulate diagnostic trouble code detecting condition after diagnostic trouble code is
recorded.
(b) To check that the malfunction is corrected when the repair is completed confirming that diagnos±
tic trouble code is no longer detected.
Malfunction: Open or Short in Sub Oxygen Sensor
± 5S±FE ENGINECIRCUIT INSPECTIONEG1±370
Page 421 of 4770
Are there any other codes (beside Code 27)
being output?Go to relevant diagnostic trouble
code chart.
DIAGNOSTIC CHART
WIRING DIAGRAM
Replace sub oxygen sensor.YES
± 5S±FE ENGINECIRCUIT INSPECTIONEG1±371
Page 422 of 4770

CIRCUIT DESCRIPTION
By a built±in sensor unit, the manifold absolute
pressure sensor detects the intake manifold absolute
pressure as a voltage.
The ECM then determines the basic injection dura±
tion and basic ignition advance angle based on this
voltage.
Since the manifold absolute pressure sensor does
not use the atmospheric pressure as a criterion, but
senses the absolute pressure inside the intake man±
ifold (the pressure in proportion to the preset abso±
lute vacuum O), it is not influenced by fluctuations
in the atmospheric, pressure due to high altitude
and other factors. This permits it to control the air±
fuel ratio at the proper level under all conditions.
If the ECM detect diagnostic trouble code ª31 ª, it operates the fail safe function, keeping the ignition
timing and fuel injection volume constant and making it possible to drive the vehicle.w
Open or short in manifold absolute pressure
sensor circuit.
wManifold absolute pressure sensor.
wECM Open or short in manifold absolute pressure sensor
circuit for 0.5 sec. or more.Diagnostic Trouble Code Detecting Condition Trouble Area
DTC 31 Manifold Absolute Pressure Sensor Circuit
DTC No.
± 5S±FE ENGINECIRCUIT INSPECTIONEG1±372
Page 423 of 4770
Check for open and short in harness and
connector between manifold absolute pressure
sensor and ECM.
Check and replace manifold absolute pressure
sensor.When diagnostic trouble code 31 is
displayed, check and replace ECM.
Repair or replace harness or
connector.
DIAGNOSTIC CHART
Check voltage of terminal PIM.Check voltage of terminal VC. Check and replace ECM.
DIA RAMWIRING DIAGRAM
± 5S±FE ENGINECIRCUIT INSPECTIONEG1±373
Page 424 of 4770
(1) Remove glove compartment.
(See page EG1±234).
(2) Turn ignition switch on.
Measure voltage between terminals VC and E2 of
engine control module connector.
Voltage: 4.5 ~ 5.5 V Check voltage between terminals VC and E2 of engine control
module connector.
Check and replace engine control module.
INSPECTION PROCEDURE
± 5S±FE ENGINECIRCUIT INSPECTIONEG1±374