6-18 ENGINE GENERAL INFORMATION AND DIAGNOSIS
P0141 HO2S heater circuit mal-
function (Sensor-2)Terminal voltage is lower than specifica-
tion at heater OFF or it is higher at heater
ON. (or heater circuit or short)2 driving
cyclesNot
applicable
P0171 Fuel system too lean Short term fuel trim or total fuel trim (short
and long terms added) is larger than spec-
ification for specified time or longer.
(fuel trim toward rich side is large.)2 driving
cyclesNot
applicable
P0172 Fuel system too rich Short term fuel trim or total fuel trim (short
and long term added) is smaller than spec-
ification for specified time or longer.
(fuel trim toward lean side is large.)2 driving
cyclesNot
applicable
P0300
P0301
P0302
P0303
P0304Random misfire detected
Cylinder 1 misfire detected
Cylinder 2 misfire detected
Cylinder 3 misfire detected
Cylinder 4 misfire detectedMisfire of such level as to cause damage
to three way catalystMIL
flashing
during
misfire
detectionNot
applicable
Misfire of such level as to deteriorate emis-
sion but not to cause damage to three way
catalyst2 driving
cyclesNot
applicable
P0325
(No.17)Knock sensor circuit mal-
functionKnock sensor circuit low input
Knock sensor circuit high input1 driving
cycle1 driving
cycle
P0335
(No.23)Crankshaft position sensor
circuit malfunctionNo signal for 2 sec. during engine cranking 1 driving
cycle1 driving
cycle
P0340
(No.15)Camshaft position sensor
circuit malfunctionNo signal during engine running 1 driving
cycle1 driving
cycle
P0400 Exhaust gas recirculation
flow malfunction detectedExcessive or insufficient EGR flow 2 driving
cyclesNot
applicable
P0420 Catalyst system efficiency
below thresholdOutput waveforms of HO2S-1 and HO2S-2
are similar.
(Time from output voltage change of
HO2S-1 to that of HO2S-2 is shorter than
specification.)2 driving
cyclesNot
applicable
P0443 Purge control valve circuit
malfunctionPurge control valve circuit is open or
shorted to ground2 driving
cyclesNot
applicable
P0480 Radiator fan control circuit
malfunctionRadiator cooling fan relay terminal voltage
is low when cooling temp. is lower than
specification2 driving
cyclesNot
applicable
P0500
(No.16)Vehicle speed sensor mal-
functionNo signal while running in “D” range or
during fuel cut at decelerating2 driving
cycles1 driving
cycle
P0505 Idle control system malfunc-
tionNo closed signal to IAC valve is detected 2 driving
cyclesNot
applicable
P0601
(No.71)Internal control module
memory check sum errorData write error (or check sum error) when
written into ECM2 driving
cycles1 driving
cycle
P1450
(No.29)Barometric pressure sen-
sor circuit malfunctionBarometric pressure is lower or higher
than specification. (or sensor malfunction)1 driving
cycle1 driving
cycle DTC
NO.DETECTING ITEM DETECTING CONDITION
(DTC will set when detecting :)MIL
(vehicle
with immo-
bilizer indi-
cator lamp)MIL
(vehicle
without
immobi-
lizer indica-
tor lamp)
6-22 ENGINE GENERAL INFORMATION AND DIAGNOSIS
VISUAL INSPECTION
Visually check following parts and systems.
INSPECTION ITEM REFERRING SECTION
Engine oil – level, leakage Section 0B
Engine coolant – level, leakage Section 0B
Fuel – level, leakage Section 0B
A/T fluid – level, leakage Section 0B
Air cleaner element – dirt, clogging Section 0B
Battery – fluid level, corrosion of terminal
Water pump belt – tension, damage Section 0B
Throttle cable – play, installation
Section 6E1 Vacuum hoses of air intake system – disconnection, looseness,
deterioration, bend
Connectors of electric wire harness – disconnection, friction
Fuses – burning Section 8
Parts – installation, bolt – looseness
Parts – deformation
Other parts that can be checked visually
Check following items at engine start, if possible
–Malfunction indicator lamp – Operation Section 6
–Charge warning lamp – Operation Section 6H
–Engine oil pressure warning lamp – Operation Section 8 (Section 6 for pressure check)
–Engine coolant temp. meter – Operation Section 8
–Fuel level meter – Operation Section 8
–Tachometer, if equipped – Operation
–Abnormal air being inhaled from air intake system
–Exhaust system – leakage of exhaust gas, noise
ENGINE GENERAL INFORMATION AND DIAGNOSIS 6-33
SCAN TOOL DATA DEFINITIONS :
FUEL SYSTEM (FUEL SYSTEM STATUS)
Air/fuel ratio feedback loop status displayed as either open or closed loop. Open indicates that ECM ignores
feedback from the exhaust oxygen sensor.
Closed indicates final injection duration is corrected for oxygen sensor feedback.
CALC LOAD (CALCULATED LOAD VALUE, %)
Engine load displayed as a percentage of maximum possible load. Value is calculated mathematically using the
formula : actual (current) intake air volume ÷ maximum possible intake air volume x 100%.
COOLANT TEMP. (ENGINE COOLANT TEMPERATURE, °C, °F)
It is detected by engine coolant temp. sensor
SHORT FT B1 (SHORT TERM FUEL TRIM, %)
Short term fuel trim value represents short term corrections to the air/fuel mixture computation. A value of 0 indi-
cates no correction, a value greater than 0 means an enrichment correction, and a value less than 0 implies an
enleanment correction.
LONG FT B1 (LONG TERM FUEL TRIM, %)
Long term fuel trim Value represents long term corrections to the air/fuel mixture computation. A value of 0 indi-
cates no correction, a value greater than 0 means an enrichment correction, and a value less than 0 implies an
enleanment correction.
MAP (INTAKE MANIFOLD ABSOLUTE PRESSURE, kPa, inHg)
It is detected by manifold absolute pressure sensor and used (among other things) to compute engine load.
ENGINE SPEED (rpm)
It is computed by reference pulses from crankshaft position sensor.
VEHICLE SPEED (km/h, MPH)
It is computed based on pulse signals from vehicle speed sensor.PNP SIGNAL (PARK/NEU-
TRAL POSITION SIGNAL)
A/T onlyIgnition switch
ONSelector lever in “P” or “N”
positionP/N Range
Selector lever in “R”, “D”,
“2” or “L” positionD Range
EGR VALVE At specified idle speed after warming up 0%
∆FUEL TANK LEVEL–0 – 100%
BAROMETRIC PRESS–Display the barometric pres-
sure
FUEL PUMP Within 3 seconds after ignition switch ON or
engine runningON
Engine stop at ignition switch ON. OFF
BRAKE SW Ignition switch
ONBrake pedal is depressing ON
Brake pedal is releasing OFF
BLOWER FAN Ignition switch
ONBlower fan switch ON ON
Blower fan switch OFF OFF
A/C MAG CLUTCH Ignition switch
ONA/C switch ON ON
A/C switch OFF OFF SCAN TOOL DATA VEHICLE CONDITION NORMAL CONDITION/
REFERENCE VALUES
6-34 ENGINE GENERAL INFORMATION AND DIAGNOSIS
IGNITION ADVANCE (IGNITION TIMING ADVANCE FOR NO.1 CYLINDER, °)
Ignition timing of NO.1 cylinder is commanded by ECM. The actual ignition timing should be checked by using
the timing light.
INTAKE AIR TEMP. (°C, °F)
It is detected by intake air temp. sensor and used to determine the amount of air passing into the intake manifold
as air density varies with temperature.
MAF (MASS AIR FLOW RATE, gm/s, lb/min)
It represents total mass of air entering intake manifold which is computed based on signals from MAP sensor,
IAT sensor, TP sensor, etc.
THROTTLE POS (ABSOLUTE THROTTLE POSITION, %)
When throttle position sensor is fully closed position, throttle opening is indicated as 0% and 100% full open
position.
OXYGEN SENSOR B1 S1 (HEATED OXYGEN SENSOR-1, V)
It indicates output voltage of HO2S-1 installed on exhaust manifold (pre-catalyst).
OXYGEN SENSOR B1 S2 (HEATED OXYGEN SENSOR-2, V)
It indicates output voltage of HO2S-2 installed on exhaust pipe (post-catalyst). It is used to detect catalyst dete-
rioration.
DESIRED IDLE (DESIRED IDLE SPEED, rpm)
The Desired Idle Speed is an ECM internal parameter which indicates the ECM requested idle. If the engine is
not running, this number is not valid.
TP SENSOR VOLT (THROTTLE POSITION SENSOR OUTPUT VOLTAGE, V)
The Throttle Position Sensor reading provides throttle valve opening information in the form of voltage.
INJ PULSE WIDTH (FUEL INJECTION PULSE WIDTH, msec.)
This parameter indicates time of the injector drive (valve opening) pulse which is output from ECM (but injector
drive time of NO.1 cylinder for multiport fuel injection).
IAC FLOW DUTY (IDLE AIR (SPEED) CONTROL DUTY, %)
This parameter indicates current flow time rate within a certain set cycle of IAC valve (valve opening rate) which
controls the amount of bypass air (idle speed).
TOTAL FUEL TRIM (%)
The value of Total Fuel Trim is obtained by putting values of short Term Fuel Trim and Long Term Fuel Trim
together. This value indicates how much correction is necessary to keep the air/fuel mixture stoichiometrical.
BATTERY VOLTAGE (V)
This parameter indicates battery positive voltage inputted from main relay to ECM.
CANIST PURGE DUTY (EVAP CANISTER PURGE FLOW DUTY, %)
This parameter indicates valve ON (valve open) time rate within a certain set cycle of EVAP purge solenoid
valve which controls the amount of EVAP purge.
0% means that the purge valve is completely closed while 100% is a fully open valve.
CLOSED THROTTLE POSITION (ON/OFF)
This parameter will read ON when throttle valve is fully closed, or OFF when the throttle is not fully closed.
FUEL CUT (ON/OFF)
ON : Fuel being cut (output signal to injector is stopped)
OFF : Fuel not being cut
ENGINE GENERAL INFORMATION AND DIAGNOSIS 6-69
DTC P0134 HEATED OXYGEN SENSOR (HO2S) CIRCUIT NO ACTIVITY
DETECTED (SENSOR-1)
WIRING DIAGRAM / CIRCUIT DESCRIPTION
Refer to DTC P0130 section.
DTC CONFIRMATION PROCEDURE
Refer to DTC P0131 section.
INSPECTION
Fig. 1 for Step 3DTC DETECTING CONDITION POSSIBLE CAUSE
Engine warmed up.
While running under other than high load and high engine speed
conditions or at specified idle speed (engine is in closed loop con-
dition), HO2S-1 output voltage is high or low continuously.
✱2 driving cycle detection logic, Continuous monitoring.“WHT” or “ORN” circuit open or short
Heated oxygen sensor malfunction
Fuel system malfunction
Exhaust gas leakage
Step Action Yes No
1Was “ENGINE DIAG. FLOW TABLE” per-
formed?Go to Step 2. Go to “ENGINE DIAG.
FLOW TABLE”.
2 Is there DTC(s) other than Fuel system
(DTC P0171/P0172) and HO2S-1 (DTC
P0134)?Go to applicable DTC
Diag. Flow Table.Go to Step 3.
3 Check HO2S-1 and Its Circuit.
1) Connect scan tool to DLC with ignition
switch OFF.
2) Warm up engine to normal operating tem-
perature and keep it at 2000 r/min. for 60
sec.
3) Repeat racing engine (Repeat depressing
accelerator pedal 5 to 6 times continuously
and take foot off from pedal to enrich and
enlean A/F mixture). See Fig. 1.
Does HO2S-1 output voltage deflect between
0.3V and over 0.6V repeatedly?Go to DTC P0171 and
P0172 Diag. Flow Table
(Fuel System Check).Check “WHT” and “ORN”
wires for open and short,
and connections for poor
connection. If wires and
connections are OK,
replace HO2S-1.
6-72 ENGINE GENERAL INFORMATION AND DIAGNOSIS
DTC P0136 HEATED OXYGEN SENSOR (HO2S) CIRCUIT MALFUNCTION
(SENSOR-2)
WIRING DIAGRAM / CIRCUIT DESCRIPTION
DTC CONFIRMATION PROCEDURE
1) Turn ignition switch OFF.
Clear DTC with ignition switch ON, check vehicle and environmental condition for :
–Altitude (barometric pressure) : 2400 m, 8000 ft or less (560 mmHg, 75 kPa or more)
–Ambient temp. : –10°C, 14°F or higher
–Intake air temp. : 70°C, 158°F or lower
–No exhaust gas leakage and loose connection
2) Warm up engine to normal operating temperature.
3) Drive vehicle under usual driving condition for 5 min. and check HO2S-2 output voltage and “short term fuel
trim” with “Data List” mode on scan tool, and write it down.
4) Stop vehicle (don’t turn ignition switch OFF).
5) Increase vehicle speed to higher than 20 mph, 32 km/h and then stop vehicle.
ECM
E11BRN
ORNC42-10 C41-13
C42 (31P) C41 (24P) G02 (17P)1 2 3 4 5 6 7 8 9
10 11 12 13 14 15 16 17 18 19 20 21
22 23 24 25 26 28 27 29 30 315 6
1 2 3 4 5 6 7
11 12
9 10 11 13 12 14 15 16
16 171 2
7 8
13 14 3 4
9 10
15 17 188
19 20 21 22 23 24
YEL
DTC DETECTING CONDITION POSSIBLE CAUSE
DTC will set when one of the following conditions is detected.
Max. output voltage of HO2S-2 is lower than specified value or
Min. output voltage is higher than specified value while vehicle
driving.
Engine is warmed up and HO2S-2 voltage is 4.5 V or more.
(circuit open)
✱2 driving cycle detection logic, monitoring once/1 driving.Exhaust gas leakage
“BRN”, “YEL” or “ORN” circuit open or
short
Heated oxygen sensor-2 malfunction
Fuel system malfunction
WARNING:
When performing a road test, select a place where there is no traffic or possibility of a traffic acci-
dent and be very careful during testing to avoid occurrence of an accident.
Road test should be carried out with 2 persons, a driver and a tester, on a level road.
ENGINE GENERAL INFORMATION AND DIAGNOSIS 6-73
6) Repeat above steps 5) 4 times.
7) Increase vehicle speed to about 50 mph (80 km/h) in 3rd gear or 2 range.
8) Release accelerator pedal and with engine brake applied, keep vehicle coasting (fuel cut condition) for
10sec. or more.
9) Stop vehicle (don’t turn ignition switch OFF) and run engine at idle for 2 min.
After this step 9), if “Oxygen Sensor Monitoring TEST COMPLETED” is displayed in “READINESS TESTS”
mode and DTC is not displayed in “DTC” mode, confirmation test is completed.
If “TEST NOT COMPLTD” is still being displayed, proceed to next step 10).
10) Drive vehicle under usual driving condition for 10 min. (or vehicle is at a stop and run engine at idle for 10
min. or longer)
11) Stop vehicle (don’t turn ignition switch OFF). Confirm test results according to “Test Result Confirmation
Flow Table” in “DTC CONFIRMATION PROCEDURE” of DTC P0420.
INSPECTION
Usual driving : Driving at 30 – 40 mph, 50 – 60 km/h including short stop according to traffic signal. (under driving condition other than high-load, high-engine
speed, rapid accelerating and decelerating)
Step Action Yes No
1Was “ENGINE DIAG. FLOW TABLE” per-
formed?Go to Step 2. Go to “ENGINE DIAG.
FLOW TABLE”.
2 Check Exhaust System for leakage, loose con-
nection and damage.
Is it good condition?Go to Step 3. Repair or replace.
3 Check HO2S-2 and Its Circuit.
Was HO2S-2 output voltage indicated on scan
tool in step 3) of DTC confirmation test less
than 1.275 V?Go to Step 4.“BRN”, “YEL” or “ORN”
circuit short to power sup-
ply circuit or HO2S-2 mal-
function.
4 Check Short Term Fuel Trim.
Did short term fuel trim very within – 20 – + 20%
range in step 3) of DTC confirmation test?Check “BRN”, “YEL” or
“ORN” wire for open and
short, and connection for
poor connection. If wire
and connection are OK,
replace HO2S-2.Check fuel system. Go to
DTC P0171/P0172 Diag.
Flow Table.
6-76 ENGINE GENERAL INFORMATION AND DIAGNOSIS
DTC P0171 FUEL SYSTEM TOO LEAN
DTC P0172 FUEL SYSTEM TOO RICH
WIRING DIAGRAM / CIRCUIT DESCRIPTION
1. Injector [a] : Signal to decrease amount of fuel injection [f] : A/F mixture becomes leaner
2. HO2S-1 [b] : Signal to increase amount of fuel injection [g] : Oxygen concentration decreases
3. WU-TWC (Warm up-three way catalytic convec-
tor)[c] : High voltage [h] : Oxygen concentration increases
4. Sensed information [d] : Low voltage
5. ECM [e] : A/F mixture becomes richer
[a]
[b]
[f] [e] [g][d]
[h][c]
1
2 5
1
2
2
3
54
+BECM
C42-9
C42-21
C42-8 C42-31
C42-1
BLU/YEL
BLU/WHT
BLU/RED
BLK/ORN
C42-3
BLK/ORN BLU/ORN
WHT
ORNC42-10C42-13
E111
DTC DETECTING CONDITION POSSIBLE CAUSE
When one of the following conditions occurs while
engine running under closed loop condition.
Air/fuel ratio too lean
(Total fuel trim (short and long terms added) is more
than 30%)
Air/fuel ratio too rich
(Total fuel trim is less than – 30%)
✱2 driving cycle detection logic, continuous monitoring.Vacuum leaks (air drawn in).
Exhaust gas leakage.
Heated oxygen sensor-1 circuit malfunction.
Fuel pressure out of specification.
Fuel injector malfunction (clogged or leakage).
MAP sensor poor performance.
ECT sensor poor performance.
IAT sensor poor performance.
TP sensor poor performance.
EVAP control system malfunction.
PCV valve malfunction.