ENGINE GENERAL INFORMATION AND DIAGNOSIS 6-27
Engine noise
Note : Before
checking mechani-
cal noise, make sure
that :
Specified spark
plug is used.
Specified fuel is
used.Improper valve lash Valve lash in Section 6A1.
Worn valve stem and guide Valves inspection in Section 6A1.
Weak or broken valve spring Valve springs inspection in Section
6A1.
Warped or bent valve Valves inspection in Section 6A1.
Worn piston, ring and cylinder bore Pistons and cylinders inspection in Sec-
tion 6A1.
Worn rod bearing Crank pin and connecting rod bearing
inspection in Section 6A1.
Worn crank pin Crank pin and connecting rod bearing
inspection in Section 6A1.
Loose connecting rod nuts Connecting rod installation in Section
6A1.
Low oil pressure Previously outlined.
Low oil pressure Previously outlined.
Worn bearing Crankshaft and bearing inspection in
Section 6A1.
Worn crankshaft journal Crankshaft and bearing inspection in
Section 6A1.
Loose bearing cap bolts Crankshaft inspection in Section 6A1.
Excessive crankshaft thrust play Crankshaft thrust play inspection in
Section 6A1.
Overheating
Inoperative thermostat Thermostat in Section 6B.
Poor water pump performance Water pump in Section 6B.
Clogged or leaky radiator Radiator in Section 6B.
Improper engine oil grade Engine oil and oil filter change in Sec-
tion 0B.
Clogged oil filter or oil strainer Oil pressure check in Section 6A1.
Poor oil pump performance Oil pressure check in Section 6A1.
Faulty radiator fan control system Radiator fan control system in Section
6E1.
Dragging brakes Trouble diagnosis in Section 5.
Slipping clutch Trouble diagnosis in Section 7C.
Blown cylinder head gasket Cylinder head in Section 6A1. Condition Possible Cause Correction
6-28 ENGINE GENERAL INFORMATION AND DIAGNOSIS
Poor gasoline mile-
age Leaks or loose connection of high-tension
cordHigh-tension cords in Section 6F1.
Faulty spark plug (improper gap, heavy
deposits and burned electrodes, etc.)Spark plugs in Section 6F1.
Malfunctioning EGR valve (if equipped) EGR system in Section 6E1.
High idle speed Refer to item “Improper engine idle
speed” previously outlined.
Poor performance of TP sensor, ECT sensor
or MAP sensorTP sensor, ECT sensor or MAP sensor
in Section 6E1.
Faulty EGR valve (if equipped) EGR system in Section 6E1.
Faulty fuel injector(s) Diagnostic Flow Table B-1.
Faulty ECM
Poor valve seating Valves inspection in Section 6A1.
Dragging brakes Trouble diagnosis in Section 5.
Slipping clutch Trouble diagnosis in Section 7C.
Thermostat out of order Thermostat in Section 6B.
Improper tire pressure Refer to Section 3F.
Low Compression Previously outlined
Excessive engine
oil consumption Blown cylinder head gasket Cylinder head in Section 6A1.
Leaky camshaft oil seals Camshaft in Section 6A1.
Sticky piston ring Piston cleaning in Section 6A1.
Worn piston and cylinder Pistons and cylinders inspection in Sec-
tion 6A1.
Worn piston ring groove and ring Pistons inspection in Section 6A1.
Improper location of piston ring gap Pistons assembly in Section 6A1.
Worn or damaged valve stem seal Valves removal and installation in Sec-
tion 6A1.
Worn valve stem Valves inspection in Section 6A1.
Engine hesitates
(Momentary lack of
response as accel-
erator is depressed.
Can occur at all
vehicle speeds.
Usually most severe
when first trying to
make vehicle move,
as from a stop sign.)Spark plug faulty or plug gap out of adjust-
mentSpark plugs in Section 6F1.
Leaky high-tension cord High-tension cords in Section 6F1.
Fuel pressure out of specification Diagnostic Flow Table B-3.
Malfunctioning EGR valve (if equipped) EGR system in section 6E1.
Poor performance of TP sensor, ECT sensor
or MAP sensorTP sensor, ECT sensor or MAP sensor
in Section 6E1.
Faulty fuel injector Diagnostic Flow Table B-1.
Faulty ECM
Engine overheating Refer to “Overheating” section.
Low compression Previously outlined.
Surge
(Engine power vari-
ation under steady
throttle or cruise.
Feels like vehicle
speeds up and
down with no
change in accelera-
tor pedal.)Leaky or loosely connected high-tension cord High-tension cords in Section 6F1.
Faulty spark plug (excess carbon deposits,
improper gap, and burned electrodes, etc.)Spark plugs in Section 6F1.
Variable fuel pressure Diagnostic Flow Table B-3.
Kinky or damaged fuel hose and lines
Faulty fuel pump (clogged fuel filter)
Malfunctioning EGR valve EGR system in Section 6E1.
Poor performance of MAP sensor MAP sensor in Section 6E1.
Faulty fuel injector Diagnostic Flow Table B-1.
Faulty ECM Condition Possible Cause Correction
ENGINE GENERAL INFORMATION AND DIAGNOSIS 6-29
Excessive detona-
tion
(Engine makes con-
tinuously sharp
metallic knocks that
change with throttle
opening. Sounds
like pop corn pop-
ping.)Faulty spark plug Spark plugs in Section 6F1.
Loose connection of high-tension cord High-tension cords in Section 6F1.
Engine overheating Refer to “Overheating” section.
Clogged fuel filter (faulty fuel pump) or fuel
linesDiagnostic Flow Table B-1 or B-2.
Air inhaling from intake manifold or throttle
body gasket
Malfunctioning EGR valve (if equipped) EGR system in Section 6E1.
Poor performance of knock sensor, ECT sen-
sor or MAP sensorKnock sensor in Section 6, ECT sensor
or MAP sensor in Section 6E1.
Faulty fuel injector(s) Diagnostic Flow Table B-1.
Faulty ECM
Excessive combustion chamber deposits Piston and cylinder head cleaning in
Section 6A1.
Engine has no
powerFaulty spark plug Spark plugs in Section 6F1.
Faulty ignition coil with ignitor Ignition coil in Section 6F1.
Leaks, loose connection or disconnection of
high-tension cordHigh-tension cords in Section 6F1.
Faulty knock sensor Knock sensor malfunction in this sec-
tion.
Clogged fuel hose or pipe Diagnostic Flow Table B-3.
Malfunctioning fuel pump Diagnostic Flow Table B-2.
Air inhaling from intake manifold gasket or
throttle body gasket
Engine overheating Refer to “Overheating” section.
Engine has no
powerMalfunctioning EGR valve (if equipped) EGR system inspection in Section 6E1.
Maladjusted accelerator cable play Accelerator cable play in Section 6E1.
Poor performance of TP sensor, ECT sensor
or MAP sensorTP sensor, ECT sensor or MAP sensor
in Section 6E1.
Faulty fuel injector(s) Diagnostic Flow Table B-1.
Faulty ECM
Dragging brakes Trouble diagnosis in Section 5.
Slipping clutch Trouble diagnosis in Section 7C.
Low compression Previously outlined. Condition Possible Cause Correction
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
6-38 ENGINE GENERAL INFORMATION AND DIAGNOSIS
TERMINAL
NO.CIRCUIT NORMAL
VOLTAGECONDITION
C411 A/C compressor clutch 0 V Ignition switch ON
2 EGR valve (stepper motor coil 1)
(if equipped)10 – 14 V Ignition switch ON
3 Throttle position sensor 0.2 – 1.0 V Ignition switch ON
Throttle valve at idle position
2.8 – 4.8 V Ignition switch ON
Throttle valve at full open position
4 Heater of HO2S-2
(Vehicle with immobilizer indicator lamp)10 – 14 V Ignition switch ON
5 Power source 10 – 14 V Ignition switch ON
6 Power source 10 – 14 V Ignition switch ON
7 Engine start switch
(Engine start signal)6 – 12 V While engine cranking
0 V Other than above
8 EGR valve (stepper motor coil 3)
(if equipped)10 – 14 V Ignition switch ON
9 EGR valve (stepper motor coil 2)
(if equipped)10 – 14 V Ignition switch ON
10 Main relay 10 – 14 V Ignition switch OFF
0.4 – 1.5 V Ignition switch ON
11 Blank––
12 Blank––
13 Heated oxygen sensor-2
(Vehicle with immobilizer indicator lamp)Refer to DTC P0130 diag. flow table
14 D-range ID-up signal (A/T) 10 – 14 V Ignition switch ON
15 R-range signal (A/T) 0 V Ignition switch ON
16 A/C (input) signal 10 – 14 V Ignition switch ON
A/C switch OFF
0 – 2 V Ignition switch ON
A/C switch ON
17 EGR valve (stepper motor coil 4)
(if equipped)10 – 14 V Ignition switch ON
18 Radiator fan control relay 10 – 14 V Ignition switch ON
Engine coolant temp. : 9.5°C or
lower (203°F)
0 – 1 V Ignition switch ON
Engine coolant temp. : 97.5°C
(208°F) or higher
19 Fuel pump relay 0 – 1 V For 2 seconds after ignition switch
ON
10 – 14 V After the above time
20–––
ENGINE GENERAL INFORMATION AND DIAGNOSIS 6-41
TERMINAL
NO.CIRCUIT NORMAL
VOLTAGECONDITION
C411 A/C compressor clutch 0 V Ignition switch ON
2–––
3–––
4–––
5 Power source 10 – 14 V Ignition switch ON
6 Power source 10 – 14 V Ignition switch ON
7 Power source for back-up 10 – 14V Anytime
8 Monitor output (Vehicle without immobi-
lizer indicator lamp)––
9 Radiator fan control relay 10 – 14 V Ignition switch ON and Engine
coolant temp. : 100°C (212°F)or
lower
0 – 1 V Ignition switch ON and Engine
coolant temp. : 102.5°C (216.5°F)
or higher
10 Main relay 10 – 14 V Ignition switch OFF
0.4 – 1.5 V Ignition switch ON
11 Ignition switch 10 – 14 V Ignition switch ON
12 Blank––
13–––
14 Diag. Switch terminal (Vehicle without
immobilizer indicator lamp)4 – 6 V Ignition switch ON
15 Test switch terminal (Vehicle without
immobilizer indicator lamp)4 – 6 V Ignition switch ON
16 A/C (input) signal 10 – 14 V Ignition switch ON
A/C switch OFF
0 – 2 V Ignition switch ON
A/C switch ON
17 Electric load signal (+) 0 V Ignition switch ON
Small light and rear defogger OFF
10 – 14 V Ignition switch ON
Small light and rear defogger OFF
18 Radiator fan control relay 10 – 14 V Ignition switch ON
Engine coolant temp. : 9.5°C or
lower (203°F)
0 – 1 V Ignition switch ON
Engine coolant temp. : 97.5°C
(208°F) or higher
19 Fuel pump relay 0 – 1 V For 2 seconds after ignition switch
ON
10 – 14 V After the above time
20 Engine start switch
(Engine start signal)6 – 12 V While engine cranking
0 V Other than above
ENGINE GENERAL INFORMATION AND DIAGNOSIS 6-43
Resistance Check
1) Disconnect ECM couplers from ECM with ignition switch
OFF.
2) Check resistance between each terminal of connectors dis-
connected.
TERMINAL RESISTANCE TABLE
For TYPE A (Refer to NOTE in “ECM VOLTAGE VALUES TABLE” for applicable model) CAUTION:
Never touch terminals of ECM itself or connect voltmeter
or ohmmeter.
CAUTION:
Be sure to connect ohmmeter probe from wire harness
side of coupler.
Be sure to turn OFF ignition switch for this check.
Resistance in table below represents that when parts
temperature is 20°C (68°F).
1. ECM coupler disconnected
2. Ohmmeter
TERMINALS CIRCUIT STANDARD
RESISTANCE
C42-7 to G02-6 HO2S-1 heater (if equipped) 5.0 – 6.4 Ω
C41-4 to G02-6 HO2S-2 heater (if equipped) 12.0 – 14.3 Ω
C42-9 to C41-5/6 No.1 injector 11.3 – 13.8 Ω
C42-21 to C41-5/6 No.2 injector 11.3 – 13.8 Ω
C42-31 to C41-5/6 No.3 injector 11.3 – 13.8 Ω
C42-8 to C41-5/6 No.4 injector 11.3 – 13.8 Ω
C41-2 to C41-5/6 EGR valve (stepper motor coil 1) (if equipped) 20 – 24 Ω
C41-9 to C41-5/6 EGR valve (stepper motor coil 2) (if equipped) 20 – 24 Ω
C41-8 to C41-5/6 EGR valve (stepper motor coil 3) (if equipped) 20 – 24 Ω
C41-17 to C41-5/6 EGR valve (stepper motor coil 4) (if equipped) 20 – 24 Ω
C42-4 to C41-5/6 EVAP canister purge valve 30 – 34 Ω
C41-19 to G02-6 Fuel pump relay 56 – 146 Ω
C41-1 to Body ground A/C compressor clutch 3 – 5.5 Ω
C41-18 to C41-5/6 Radiator fan control relay No.1 56 – 146 Ω
C41-10 to G02-17 Main relay 56 – 146 Ω
C42-1 to Body ground Ground Continuity
C42-2 to Body ground Ground Continuity
C42-3 to Body ground Ground Continuity
6-44 ENGINE GENERAL INFORMATION AND DIAGNOSIS
For TYPE B (Refer to NOTE in “ECM VOLTAGE VALUES TABLE” for applicable model.)
TERMINALS CIRCUIT STANDARD
RESISTANCE
C42-7 to C41-11 HO2S-1 heater (if equipped) 5.0 – 6.4 Ω
C41-4 to C41-11 HO2S-2 heater (if equipped) 12.0 – 14.3 Ω
C42-9 to C41-5/6 No.1 injector 11.3 – 13.8 Ω
C42-21 to C41-5/6 No.2 injector 11.3 – 13.8 Ω
C42-31 to C41-5/6 No.3 injector 11.3 – 13.8 Ω
C42-8 to C41-5/6 No.4 injector 11.3 – 13.8 Ω
C42-18 to C41-5/6 EGR valve (stepper motor coil 1) (if equipped) 20 – 24 Ω
C42-29 to C41-5/6 EGR valve (stepper motor coil 2) (if equipped) 20 – 24 Ω
C42-17 to C41-5/6 EGR valve (stepper motor coil 3) (if equipped) 20 – 24 Ω
C42-28 to C41-5/6 EGR valve (stepper motor coil 4) (if equipped) 20 – 24 Ω
C42-4 to C41-5/6 EVAP canister purge valve 30 – 34 Ω
C41-19 to G02-6 Fuel pump relay 56 – 146 Ω
C41-1 to Body ground A/C compressor clutch 3 – 5.5 Ω
C41-18 to C41-5/6 Radiator fan control relay No.1 56 – 146 Ω
C41-10 to C41-7 Main relay 56 – 146 Ω
C42-1 to Body ground Ground Continuity
C42-2 to Body ground Ground Continuity
C42-3 to Body ground Ground Continuity