MEF036D
SEF233G
SEF234G
IntroductionNJEC0036The engine has an ECM to control major systems such as fuel
control, ignition control, idle air control system, etc. The ECM
accepts input signals from sensors and instantly drives actuators.
It is essential that both input and output signals are proper and
stable. At the same time, it is important that there are no problems
such as vacuum leaks, fouled spark plugs, or other problems with
the engine.
It is much more difficult to diagnose a problem that occurs intermit-
tently rather than continuously. Most intermittent problems are
caused by poor electric connections or improper wiring. In this
case, careful checking of suspected circuits may help prevent the
replacement of good parts.
A visual check only may not find the cause of the problems. A road
test with CONSULT-II (or GST) or a circuit tester connected should
be performed. Follow the ªWork Flowº on EC-96.
Before undertaking actual checks, take a few minutes to talk with
a customer who approaches with a driveability complaint. The cus-
tomer can supply good information about such problems, espe-
cially intermittent ones. Find out what symptoms are present and
under what conditions they occur. A ªDiagnostic Worksheetº like the
example on next page should be used.
Start your diagnosis by looking for ªconventionalº problems first.
This will help troubleshoot driveability problems on an electronically
controlled engine vehicle.
SEF907L
DIAGNOSTIC WORKSHEETNJEC0036S01There are many operating conditions that lead to the malfunction
of engine components. A good grasp of such conditions can make
trouble-shooting faster and more accurate.
In general, each customer feels differently about a problem. It is
important to fully understand the symptoms or conditions for a
customer complaint.
Utilize a diagnostic worksheet like the one on the next page in order
to organize all the information for troubleshooting.
Some conditions may cause the malfunction indicator lamp to
come on steady or blink and DTC to be detected.
Example:
Vehicle ran out of fuel, which caused the engine to misfire.
TROUBLE DIAGNOSIS Ð INTRODUCTIONQG
EC-94
DESCRIPTION FOR WORK FLOWNJEC0563S01
STEP DESCRIPTION
STEP IGet detailed information about the conditions and the environment when the incident/symptom occurred using
the ªDIAGNOSTIC WORK SHEETº, EC-95.
STEP IIBefore confirming the concern, check and write down (print out using CONSULT-II or GST) the (1st trip) DTC
and the (1st trip) freeze frame data, then erase the DTC and the data. (Refer to EC-68, EC-71.) The (1st trip)
DTC and the (1st trip) freeze frame data can be used when duplicating the incident at STEP III & IV.
If the incident cannot be verified, perform ªTROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENTº, EC-144.
Study the relationship between the cause, specified by (1st trip) DTC, and the symptom described by the cus-
tomer. (The ªSymptom Matrix Chartº will be useful. See EC-124.)
Also check related service bulletins for information.
STEP IIITry to confirm the symptom and under what conditions the incident occurs.
The ªDIAGNOSTIC WORK SHEETº and the freeze frame data are useful to verify the incident. Connect CON-
SULT-II to the vehicle in DATA MONITOR (AUTO TRIG) mode and check real time diagnosis results.
If the incident cannot be verified, perform ªTROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENTº, EC-144.
If the malfunction code is detected, skip STEP IV and perform STEP V.
STEP IVTry to detect the (1st trip) DTC by driving in (or performing) the ªDTC Confirmation Procedureº. Check and read
the (1st trip) DTC and (1st trip) freeze frame data by using CONSULT-II or GST.
During the (1st trip) DTC verification, be sure to connect CONSULT-II to the vehicle in DATA MONITOR (AUTO
TRIG) mode and check real time diagnosis results.
If the incident cannot be verified, perform ªTROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENTº, EC-144.
In case the ªDTC Confirmation Procedureº is not available, perform the ªOverall Function Checkº instead. The
(1st trip) DTC cannot be displayed by this check, however, this simplified ªcheckº is an effective alternative.
The ªNGº result of the ªOverall Function Checkº is the same as the (1st trip) DTC detection.
STEP VTake the appropriate action based on the results of STEP I through IV.
If the malfunction code is indicated, proceed to TROUBLE DIAGNOSIS FOR DTC PXXXX.
If the normal code is indicated, proceed refer to ªBASIC INSPECTIONº, EC-98. If CONSULT-II is available, per-
form ªDATA MONITOR (SPEC)º mode with CONSULT-II and proceed to the ªTROUBLE DIAGNOSIS Ð SPECI-
FICATION VALUEº. (Refer to EC-140.) (If malfunction is detected, proceed to ªREPAIR/REPLACEº.) Then per-
form inspections according to the Symptom Matrix Chart. (Refer to EC-124.)
STEP VIIdentify where to begin diagnosis based on the relationship study between symptom and possible causes.
Inspect the system for mechanical binding, loose connectors or wiring damage using (tracing) ªHarness Layoutsº.
Gently shake the related connectors, components or wiring harness with CONSULT-II set in ªDATA MONITOR
(AUTO TRIG)º mode.
Check the voltage of the related ECM terminals or monitor the output data from the related sensors with CON-
SULT-II. Refer to EC-132.
The ªDiagnostic Procedureº in EC section contains a description based on open circuit inspection. A short circuit
inspection is also required for the circuit check in the Diagnostic Procedure. For details, refer to GI section
(ªHOW TO PERFORM EFFICIENT DIAGNOSIS FOR AN ELECTRICAL INCIDENTº, ªCircuit Inspectionº).
Repair or replace the malfunction parts.
If malfunctioning part cannot be detected, perform ªTROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENTº,
EC-144.
STEP VIIOnce you have repaired the circuit or replaced a component, you need to run the engine in the same conditions
and circumstances which resulted in the customer's initial complaint.
Perform the ªDTC Confirmation Procedureº and confirm the normal code [DTC No. P0000] is detected. If the
incident is still detected in the final check, perform STEP VI by using a different method from the previous one.
Before returning the vehicle to the customer, be sure to erase the unnecessary (already fixed) (1st trip) DTC in
ECM and TCM (Transmission control module). (Refer to EC-68, EC-71.)
TROUBLE DIAGNOSIS Ð INTRODUCTIONQG
Work Flow (Cont'd)
EC-97
Basic InspectionNJEC1785MODELS WITH THROTTLE POSITION SWITCHNJEC1785S01Precaution:
Perform Basic Inspection without electrical or mechanical
loads applied;
+Headlamp switch is OFF,
On vehicle equipped with daytime light systems, set lighting
switch to the 1st position to light only small lamps.
+Air conditioner switch is OFF,
+Rear window defogger switch is OFF,
+Steering wheel is in the straight-ahead position, etc.
1 INSPECTION START
1. Check service records for any recent repairs that may indicate a related problem, or a current need for scheduled
maintenance.
2. Open engine hood and check the following:
+Harness connectors for improper connections
+Vacuum hoses for splits, kinks and improper connections
+Wiring for improper connections, pinches and cuts
+Air cleaner clogging
+Hoses and ducts for leaks
SEF983U
©GO TO 2.
2 CHECK THROTTLE OPENER OPERATION-I
Confirm that there is a clearance between throttle drum and stopper.
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OK or NG
OK©GO TO 4.
NG©GO TO 3.
TROUBLE DIAGNOSIS Ð BASIC INSPECTIONQG
Basic Inspection
EC-98
35 CHECK IGNITION TIMING AGAIN
Check ignition timing again. Refer to Test No. 31.
OK or NG
OK©GO TO 37.
NG©GO TO 36.
36 CHECK TIMING CHAIN INSTALLATION
Check timing chain installation. Refer to EM-27, ªInstallationº.
OK or NG
OK©GO TO 34.
NG©1. Repair the timing chain installation.
2. GO TO 32.
37 ERASE UNNECESSARY DTC
After this inspection, unnecessary DTC No. might be displayed.
Erase the stored memory in ECM and TCM (Transmission control module).
Refer to ªHow to Erase Emission-Related Diagnostic Informationº, EC-68 or EC-75 and AT-50, ªHOW TO ERASE DTCº.
OK or NG
©INSPECTION END
MODELS WITHOUT THROTTLE POSITION SWITCHNJEC1785S02Precaution:
Perform Basic Inspection without electrical or mechanical
loads applied;
+Headlamp switch is OFF,
On vehicle equipped with daytime light system, set lighting
switch to the 1st position to light only small lamps.
+Air conditioner switch is OFF,
+Rear window defogger switch is OFF,
+Steering wheel is in the straight-ahead position, etc.
1 INSPECTION START
1. Check service records for any recent repairs that may indicate a related problem, or a current need for scheduled
maintenance.
2. Open engine hood and check the following:
+Harness connectors for improper connections
+Vacuum hoses for splits, kinks and improper connections
+Wiring for improper connections, pinches and cuts
+Air cleaner clogging
+Hoses and ducts for leaks
SEF983U
©GO TO 2.
TROUBLE DIAGNOSIS Ð BASIC INSPECTIONQG
Basic Inspection (Cont'd)
EC-113
Fail-safe Chart=NJEC0040The ECM enters fail-safe mode if any of the following malfunctions is detected due to the open or short cir-
cuit. When the ECM enters the fail-safe mode, the MI illuminates.
DTC No.
Detected items Engine operating condition in fail-safe mode CON-
SULT-II
GSTECM*1
P0100 0100 Mass air flow sensor
circuitEngine speed will not rise more than 2,400 rpm due to the fuel cut.
P0115 0115 Engine coolant tempera-
ture sensor circuitEngine coolant temperature will be determined by ECM based on the time
after turning ignition switch ªONº or ªSTARTº.
CONSULT-II displays the engine coolant temperature decided by ECM.
The radiator fan operates.
ConditionEngine coolant temperature decided
(CONSULT-II display)
Just as ignition switch is turned
ON or Start40ÉC (104ÉF)
More than approx. 4 minutes
after ignition ON or Start80ÉC (176ÉF)
Except as shown above40 - 80ÉC (104 - 176ÉF)
(Depends on the time)
P0120 0120 Throttle position sensor
circuitThrottle position will be determined based on the injected fuel amount and
the engine speed. Therefore, acceleration will be poor.
Condition Driving condition
When engine is idling Normal
When accelerating Poor acceleration
Unable to
access
ECMUnable to
access
Diagnostic
Test Mode
IIECMECM fail-safe activating condition
The computing function of the ECM was judged to be malfunctioning.
When the fail-safe system activates (i.e., if the ECM detects a malfunction
condition in the CPU of ECM), the MI on the instrument panel lights to warn
the driver.
However it is not possible to access ECM and DTC cannot be confirmed.
Engine control with fail-safe
When ECM fail-safe is operating, fuel injection, ignition timing, fuel pump
operation and IACV-AAC valve operation are controlled under certain limita-
tions.
ECM fail-safe operation
Engine speedEngine speed will not rise more than
3,000 rpm
Fuel injectionSimultaneous multiport fuel injection sys-
tem
Ignition timing Ignition timing is fixed at the preset value
Fuel pumpFuel pump relay is ªONº when engine is
running and ªOFFº when engine stalls
IACV-AAC valve Full open
Cooling fansCooling fan relay ªONº (High speed condi-
tion) when engine is running, and ªOFFº
when engine stalls.
Replace ECM, if ECM fail-safe condition is confirmed.
*: In Diagnostic Test Mode II (Self-diagnostic results) (If so equipped)
TROUBLE DIAGNOSIS Ð GENERAL DESCRIPTIONQG
Fail-safe Chart
EC-123
Symptom Matrix ChartNJEC0041SYSTEM Ð ENGINE CONTROL SYSTEMNJEC0041S01
SYMPTOM
Reference
page
HARD/NO START/RESTART (EXCP. HA)
ENGINE STALL
HESITATION/SURGING/FLAT SPOT
SPARK KNOCK/DETONATION
LACK OF POWER/POOR ACCELERATION
HIGH IDLE/LOW IDLE
ROUGH IDLE/HUNTING
IDLING VIBRATION
SLOW/NO RETURN TO IDLE
OVERHEATS/WATER TEMPERATURE HIGH
EXCESSIVE FUEL CONSUMPTION
EXCESSIVE OIL CONSUMPTION
BATTERY DEAD (UNDER CHARGE)
Warranty symptom code AA AB AC AD AE AF AG AH AJ AK AL AM HA
Fuel Fuel pump circuit11232 22 3 2EC-464
Fuel pressure regulator sys-
tem334444444 4EC-39
Injector circuit11232 22 2EC-447
Evaporative emission sys-
tem334444444 4EC-33
Air Positive crankcase ventila-
tion system334444444 41EC-37
Incorrect idle speed adjust-
ment3 3 1 1 1 1 1 EC-41
IACV-AAC valve circuit112332222 2 2EC-313
Ignition Incorrect ignition timing
adjustment33111 11 1EC-41
Ignition circuit11222 22 2EC-451
EGR EGR volume control valve
circuit2233 3EC-293
EGR system212333223 3EC-285,
293, 353
Main power supply and ground circuit22333 33 23 2EC-145
Air conditioner circuit223333333 3 2HAsection
1 - 6: The numbers refer to the order of inspection.
(continued on next page)
TROUBLE DIAGNOSIS Ð GENERAL DESCRIPTIONQG
Symptom Matrix Chart
EC-124
CONSULT-II Reference Value in Data Monitor
Mode
NJEC0042Remarks:
+Specification data are reference values.
+Specification data are output/input values which are detected or supplied by the ECM at the connector.
* Specification data may not be directly related to their components signals/values/operations.
(i.e., Adjust ignition timing with a timing light before monitoring IGN TIMING. Specification data might be displayed even when igni-
tion timing is not adjusted to specification. This IGN TIMING monitors the data calculated by the ECM according to the input signals
from the crankshaft position sensor and other ignition timing related sensors.)
+If the real-time diagnosis results are NG, and the on board diagnostic system results are OK, when diagnosing the mass air flow sensor,
first check to see if the fuel pump control circuit is normal.
MONITOR ITEM CONDITION SPECIFICATION
ENG SPEED+Tachometer: Connect
+Run engine and compare tachometer indication with the CONSULT-II
value.Almost the same speed as the
CONSULT-II value.
MAS A/F SE-B1+Engine: After warming up
+Air conditioner switch: OFF
+Shift lever: ªNº
+No-loadIdle 1.0 - 1.7V
2,500 rpm 1.5 - 2.1V
B/FUEL SCHDL+Engine: After warming up
+Air conditioner switch: OFF
+Shift lever: ªNº
+No-loadIdle 1.5 - 3.0 msec
2,000 rpm 1.2 - 3.0 msec
A/F ALPHA-B1+Engine: After warming upMaintaining engine speed at 2,000
rpm75 - 125%
COOLAN TEMP/S+Engine: After warming up More than 70ÉC (158ÉF)
HO2S1 (B1)
+Engine: After warming upMaintaining engine speed at 2,000
rpm0 - 0.3V¨0.6 - 1.0V
HO2S1 MNTR (B1)LEAN¨RICH
Changes more than 5 times
during 10 seconds.
HO2S2 (B1)
+Engine: After warming upRevving engine from idle to 3,000
rpm quickly0 - 0.3V¨0.6 - 1.0V
HO2S2 MNTR (B1)LEAN¨RICH
VHCL SPEED SE+Turn drive wheels and compare speedometer indication with the CON-
SULT-II valueAlmost the same speed as the
CONSULT-II value
BATTERY VOLT+Ignition switch: ON (Engine stopped) 11 - 14V
THRTL POS SEN+Engine: Idle Throttle valve fully closed 0.15 - 0.85V
+Ignition switch: ON
(Engine stopped)Throttle valve fully opened 3.5 - 4.7V
EGR TEMP SEN*+Engine: After warming up Less than 4.5V
START SIGNAL+Ignition switch: ON®START®ON OFF®ON®OFF
CLSD THL POS
CLSD THL/P SW*+Engine: Idle Throttle valve: Idle position ON
+Ignition switch: ON
(Engine stopped)Throttle valve: Slightly open OFF
AIR COND SIG+Engine: After warming up, idle
the engineA/C switch ªOFFº OFF
A/C switch ªONº
(Compressor operates)ON
P/N POSI SW+Ignition switch: ONShift lever ªPº or ªNº ON
Except above OFF
TROUBLE DIAGNOSIS Ð GENERAL DESCRIPTIONQG
CONSULT-II Reference Value in Data Monitor Mode
EC-128
MONITOR ITEM CONDITION SPECIFICATION
PW/ST SIGNAL+Engine: After warming up, idle
the engineSteering wheel in neutral position
(forward direction)OFF
The steering wheel is turned ON
LOAD SIGNAL+Engine: runningRear window defogger or headlamp
ªONºON
Except the above OFF
IGNITION SW+Ignition switch: ON®OFF ON®OFF
HEATER FAN SW+Heater fan switch is ªONº ON
+Heater fan switch is ªOFFº OFF
INJ PULSE-B1+Engine: After warming up
+Air conditioner switch: OFF
+Shift lever: ªNº
+No-loadIdle 2.0 - 3.5 msec
2,000 rpm 1.5 - 3.5 msec
IGN TIMING+Engine: After warming up
+Air conditioner switch: OFF
+Shift lever: ªNº
+No-loadIdleM/T: 8ɱ5É BTDC
A/T: 10ɱ5É BTDC
2,000 rpm Approx. 30É BTDC
CAL/LD VALUE+Engine: After warming up
+Air conditioner switch: OFF
+Shift lever: ªNº
+No-loadIdle Not used
2,500 rpm Not used
ABSOL TH´P/S+Engine: Idle Throttle valve fully closed 0.0É
+Ignition switch: ON
(Engine stopped)Throttle valve fully opened Approx. 80É
MASS AIRFLOW+Engine: After warming up
+Air conditioner switch: OFF
+Shift lever: N
+No-loadIdle 1.0 - 4.0 g´m/s
2,500 rpm 5.0 - 10.0 g´m/s
IACV-AAC/V+Engine: After warming up
+Air conditioner switch: OFF
+Shift lever: ªNº
+No-loadIdle 5 - 25 steps
2,000 rpm Ð
PURG VOL C/V+Engine: After warming up
+No-loadIdle 0%
Revving engine Ð
EGR VOL CON/V*+Engine: After warming up
+Shift lever: ªNº
+No-loadIdle 0 step
Revving engine up to 3,000 rpm
quickly1 - 10 steps
INT/V SOL-B1+Engine: After warming up
+Lift up drive wheelsIdle OFF
Suitable gear position except ªPº or
ªNº and revving engineON (Momentarily)
AIR COND RLY+Air conditioner switch: OFF®ON OFF®ON
FUEL PUMP RLY+Ignition switch is turned to ON (Operates for 1 second)
+Engine running and cranking
+When engine is stopped (stops in 1.5 seconds)ON
+Except as shown above OFF
TROUBLE DIAGNOSIS Ð GENERAL DESCRIPTIONQG
CONSULT-II Reference Value in Data Monitor Mode (Cont'd)
EC-129