MPI – Troubleshooting13-6
TROUBLESHOOTING
DIAGNOSIS TROUBLESHOOTING FLOW
Refer to GROUP 00 – How to Use Troubleshooting/Inspection
Service Points.
DIAGNOSIS FUNCTION
ENGINE WARNING LAMP (CHECK ENGINE LAMP)
If an abnormality occurs in any of the following items related
to the Multipoint Fuel Injection (MPI) system, the engine
warning lamp will illuminate.
If the lamp remains illuminated or if the lamp illuminates while
the engine is running, check the diagnosis code output.
Engine warning lamp inspection items
Engine-ECU
Air flow sensor
Intake air temperature sensor
Throttle position sensor
Engine coolant temperature sensor
Crank angle sensor
Camshaft position sensor
Barometric pressure sensor
Detonation sensor
Injector
Ignition coil, power transister unit
METHOD OF READING AND ERASING DIAGNOSIS
CODES
Refer to GROUP 00 – How to Use Troubleshooting/Inspection
Service Points.
INSPECTION USING MUT-II DATA LIST AND
ACTUATOR TESTING
1. Carry out inspection by connecting the MUT-II.
If there is an abnormality, check and repair the chassis
harnesses and components.
2. After repairing, check that the abnormal input and output
have returned to normal as a result of the repairs.
3. Erase the diagnosis code memory.
4. Remove the MUT-II and carry out a road test to confirm
that the problem has disappeared.
Engine warning lamp
(check engine lamp)
MPI – Troubleshooting13-8
3. INSPECTION CHART FOR DIAGNOSIS CODES
Code No.Diagnosis itemReference page
12Air flow sensor system13-8
13Intake air temperature sensor system13-9
14Throttle position sensor system13-9
21Engine coolant temperature sensor system13-10
22Crank angle sensor system13-11
23Camshaft position sensor system13-12
24Vehicle speed sensor system13-13
25Barometric pressure sensor system13-14
31Detonation sensor system13-15
41Injector system13-15
44Ignition coil and power transistor unit system13-16
64Alternator FR terminal system13-17
INSPECTION PROCEDURE FOR DIAGNOSIS CODES
Code No. 12 Air flow sensor systemProbable cause
Range of Check
Engine speed is 500 r/min or more.
Set conditions
Sensor output frequency is 3 Hz or less for 4 seconds.Malfunction of the air flow sensor
Improper connector contact, open or short-circuited
harness wire of the air flow sensor
Malfunction of the engine-ECU
Measure at the air flow sensor con-
nector A-25.
Connect the connector. (Use
the test harness: MB991709)
1. Voltage between 3 and earth
(Engine: Idling)
OK:2.2–3.2 V
2. Voltage between 7 and earth
OK:0–1 V (Engine: idling)
6–9 V (2,000 r/min)
OK
Replace the engine-ECU.1. NG
Check the air flow sensor circuit.
(Refer to P.13-55, INSPECTION
PROCEDURE 48.)
2. NG
Measure at the engine-ECU con-
nector B-59.
Connect the connector.
Voltage between 19 and earth
(Ignition switch: ON)
OK:6–9 V
OK
Check the following connector:
B-59
OK
Check trouble symptom.
NG
Replace the engine-ECU.NG
Check the following connector:
A-25NG
Repair
OK
Check trouble symptom.
NG
NG
Repair
Replace the air flow sensor.
MPI – Troubleshooting13-15
Code No. 31 Detonation sensor systemProbable cause
Range of Check
Ignition switch: ON
Excluding 60 seconds after the ignition switch is turned to ON or immediately
after the engine starts.
Engine speed is approx. 5,000 r/min or more
Set conditions
The change in the detonation sensor output voltage (detonation sensor peak voltage
at each 1/2 revolution of the crankshaft) is less than 0.06 V for 200 times in
succession.Malfunction of the detonation sensor
Improper connector contact, open or short-circuited
harness wire of the detonation sensor circuit
Malfunction of the engine-ECU
Measure at the detonation sensor con-
nector A-96.
Disconnect the connector and
measure at the harness side.
Continuity between 2 and earth
OK:ContinuityOKCheck the following connector:
B-62NG
Repair
OK
Check trouble symptom.
NG
Check the harness wire between the
engine-ECU and the detonation sensor
connector.OKReplace the detonation sensor.
Check trouble symptom.
NG
Replace the engine-ECU.
NG
Repair
NG
Check the harness wire between the
detonation sensor and earth, and repair
if necessary.
Code No. 41 Injector systemProbable cause
Range of Check
Engine speed is approx. 50–1,000 r/min
The throttle position sensor output voltage is 1.15 V or less.
Actuator test by MUT-II is not carried out.
Set conditions
Surge voltage of injector coil is not detected for 4 seconds.Malfunction of the injector
Improper connector contact, open or short-circuited
harness wire of the injector circuit
Malfunction of the engine-ECU
OK
Check trouble symptom.NGCheck the harness wire between the
resistor and the injector connector, and
repair if necessary.
Check the injector control circuit.
(Refer to P.13-55, INSPECTION PRO-
CEDURE 50.)OK
OK
Measure at the injector connectors
A-53, A-54, A-55, A-56
Disconnect the connector, and
measure at the harness side.
Voltage between 1 and earth
(Ignition switch: ON)
OK:System voltageNGCheck the following connector:
A-125NG
Repair
OK
Measure at the resistor connector
A-125.
Disconnect the connector, and
measure at the harness side.
Voltage between 3 and earth
(Ignition switch: ON)
OK:System voltageNGCheck the harness wire between the
control relay and the resistor connector,
and repair if necessary.
Check the injector. (Refer to P.13-34.)*
Check the resistor. (Refer to P.13-34.)*NG
Replace
NOTE
*: Refer to Workshop Manual for LANCER EVOLUTION-IV and EVOLUTION-V (Pub. No. S9806CNCP9).
MPI – Troubleshooting13-16
Code No. 44 Ignition coil and power transistor unit systemProbable cause
Range of Check
Engine speed is approx. 50–4,000 r/min
Engine is not cranking.
Set conditions
Abnormal rotation due to misfire is detected by crank angle sensor (Either one
of coils fails).Malfunction of the ignition coil
Improper connector contact, open or short-circuited
harness wire of the ignition primary circuit
Malfunction of the engine-ECU
OK
OK
Check trouble symptom.
Measure at the ignition coil connectors
A-110, A-111
Disconnect the connector, and
measure at the harness.
1. Voltage between 1 and earth
(Ignition switch: ON)
OK: System voltage
2. Voltage between 3 and earth
(Engine: Cranking)
OK: 0.5–4.0 V
3. Continuity between the 2 and earth
OK: Continuity1. NGCheck the following connectors:
B-65, B-76OKCheck trouble symptom.
NG
Check the harness wire between the
ignition coil and ignition switch connec-
tor, and repair if necessary.
2. NGCheck the following connector: B-59NG
Repair
NG
Check the harness wire between the
engine-ECU and ignition coil connector.OKReplace the engine-ECU.
NG
Repair
3. NG
Check the harness wire between the
ignition coil connector and earth, and
repair if necessary.
Check the following connectors:
A-110, A-111NG
Repair
Check trouble symptom.
NG
Check the following items.
Check the spark plugs, spark plug
cables.
Check the compression pressure.
NG
Repair
Check the ignition coil. (Refer to
GROUP 16 – IGNITION SYSTEM.)NG
Replace
OK
OK
MPI – Troubleshooting13-22
INSPECTION PROCEDURE 5
No initial combustion (starting impossible)
Probable cause
In cases such as the above, the cause is probably that a spark plug is defective,
or that the supply of fuel to the combustion chamber is defective.
In addition, foreign materials (water, kerosene, etc.) may be mixed with the fuel.Malfunction of the ignition system
Malfunction of the fuel pump system
Malfunction of the injectors
Malfunction of the engine-ECU
Foreign materials in fuel
Check system voltage when cranking.
OK:8 V or higherNGCheck the battery.
OK
MUT-II: Inspection of no initial combustion.
(Refer to P.13-47, INSPECTION PROCEDURE 37.)
OK
Can any sound be heard from the injectors when cranking (check
using a soundscope)?NGCheck the injector system. (Refer to P.13-15, INSPECTION PRO-
CEDURE FOR DIAGNOSIS CODE 41.)
OK
Ignition system: Inspection of no initial combustion.
(Refer to P.13-47, INSPECTION PROCEDURE 38.)
OK
Check the following items.
Check the ignition coil, spark plugs, spark plug cables.
Check if the injectors are clogged.
Check if foreign materials (water, alcohol, etc.) got into fuel.
Check the compression pressure.
MPI – Troubleshooting13-23
INSPECTION PROCEDURE 6
Initial combustion but no complete combustion
(starting impossible)
Probable cause
In such cases as the above, the cause is probably that the spark plugs are generating
sparks but the sparks are weak, or the initial mixture for starting is not appropriate.Malfunction of the ignition system
Malfunction of the injector system
Foreign materials in fuel
Poor compression
Malfunction of the engine-ECU
Check system voltage when cranking.
OK:8 V or higherNGCheck the battery.
OK
MUT-II: Check if uncompleted combustion occurs.
(Refer to P.13-48, INSPECTION PROCEDURE 39.)
OK
Can any sound be heard from the injectors when cranking (check
using a soundscope)?NGCheck the injector system, (Refer to P.13-15, INSPECTION PRO-
CEDURE FOR DIAGNOSIS CODE 41.)
OK
Is starting good if the engine is cranked with the accelerator pedal
slightly depressed?Ye sCheck ISC servo for op-
eration sound. NGCheck the ISC servo sys-
tem. (Refer to P.13-44, IN-
SPECTION PROCE-
DURE 33.)
OK
Clean the throttle valve area.
Adjust the fixed SAS. (Refer to P.13-30.)*
No
Check the ignition timing when cranking.
OK:Approx. 5BTDCNGCheck that the crank angle sensor and the timing belt cover are
installed properly.
OK
Check the following items.
Check the ignition coil, spark plugs, spark plug cables.
Check the injectors for clogging and leakage.
Check the compression pressure.
Check fuel lines for clogging.
Check if foreign materials (water, alcohol, etc.) got into fuel.
NOTE
*: Refer to Workshop Manual for LANCER EVOLUTION-IV and EVOLUTION-V (Pub. No. S9806CNCP9).
MPI – Troubleshooting13-24
INSPECTION PROCEDURE 7
Long time to start (Improper starting)
Probable cause
In cases such as the above, the cause is probably that the spark is weak and ignition
is difficult, the initial mixture for starting is not appropriate, or sufficient compression
pressure is not being obtained.Malfunction of the ignition system
Malfunction of the injector system
Inappropriate gasoline use
Poor compression
Check system voltage when cranking
OK:8 V or higherNGCheck the battery.
OK
MUT-II: Check if uncomplete combustion occurs.
(Refer to P.13-48, INSPECTION PROCEDURE 39.)
OK
Can any sound be heard from the injectors when cranking (check
using a soundscope)?NGCheck the injector system. (Refer to P.13-15, INSPECTION PRO-
CEDURE FOR DIAGNOSIS CODE 41.)
OK
Check the ignition timing when cranking.
OK:Approx. 5BTDCNGCheck that the crank angle sensor and the timing belt cover are
installed properly.
OK
Check the following items.
Check the ignition coil, spark plugs, spark plug cables.
Check the injectors for clogging and leakage.
Check the compression pressure.
Check if foreign materials (water, alcohol, etc.) got into fuel.
MPI – Troubleshooting13-25
INSPECTION PROCEDURE 8
Unstable idling (Rough idling, hunting)
Probable cause
In cases as the above, the cause is probably that the ignition system, air/fuel mixture,
idle speed control (ISC) or compression pressure is defective.
Because the range of possible causes is broad, inspection is narrowed down to simple
items.Malfunction of the ignition system
Malfunction of air-fuel ratio control system
Malfunction of the ISC servo system
Poor compression
Drawing air into exhaust system
Secondary air backflow to the intake system
Were the battery terminals disconnected recently?Ye sAfter warming-up, let the engine run at idling for about 10 minutes.
No
MUT-II Self-Diag code
Are diagnosis codes displayed?Ye sRefer to P.13-8, INSPECTION CHART FOR DIAGNOSIS CODES.
No
Does idling speed fluctuate excessively?Ye sCheck if hunting occurs.
(Refer to P.13-48, INSPECTION PROCEDURE 40.)
No
Check the ISC servo for operation sound.NGCheck the ISC servo system.
(Refer to P.13-44, INSPECTION PROCEDURE 33.)
OK
Check the injector for operation.NGCheck the injector system. (Refer to P.13-15, INSPECTION PRO-
CEDURE FOR DIAGNOSIS CODE 41.)
OK
MUT-II: Check if idling speed is unstable.
(Refer to P.13-49, INSPECTION PROCEDURE 41.)
OK
Check the ignition timing.
(Refer to GROUP 11 – Engine Adjustment.)*NGCheck that the crank angle sensor and the timing belt cover are
installed properly.
OK
Check the following items.
Check the ignition coil, spark plugs, spark plug cables.
Check the secondary air supply system. (Ensure that there is no back flow of secondary air into the intake system.)
Check the compression pressure.
Check if foreign materials (water, alcohol, etc.) got into fuel.
NOTE
*: Refer to Workshop Manual for LANCER EVOLUTION-IV and EVOLUTION-V (Pub. No. S9806CNCP9).