MPI – General13-3
MPI System Diagram
1 Injector
2 ISC servo
3 Fuel pressure control valve
4 Waste gate solenoid valve
5 Secondary air control solenoid valve
Control relay
Fuel pump relay
A/C relay
Ignition coil
Exhaust temperature warning lamp
Engine warning lamp
Diagnosis output
Alternator G terminal
Fan motor relay
Tachometer
Fuel pump relay No.2 1 Oxygen sensor
2 Air flow sensor
3 Intake air temperature sensor
4 Throttle position sensor
5 Idle switch
6 Camshaft position sensor
7 Crank angle sensor
8 Barometric pressure sensor
9 High temperature sensor
10 Engine coolant temperature sensor
11 Detonation sensor
Power supply voltage
Ignition switch-IG
Ignition switch-ST
Vehicle speed sensor
A/C switch
Power steering fluid pressure switch
Alternator FR signalEngine ECU
1 Oxygen sensor
2 Air flow sensor3
Intake air tem-
perature sensor
4,
5
6 Camshaft position
sensor
7 Crank angle sensor 8 Barometric
pressure sensor
9 High temperature
sensor 10 Coolant temperature sensor
11 Detonation sensor1 Injector 2 ISC servo
3 Fuel pressure
control valve
4 Waste gate
solenoid valve 5 Secondary air
control solenoid
valveCanister
Check valveFrom
fuel
tank
Throttle position
sensor (with a
built-in
idle
switch)
Secondary
air valve
AirTo fuel
tankFuel
pressure
regulatorFrom
fuel
pump
Waste gate
actuator
Catalytic converter
MPI – Special Tools13-5
SPECIAL TOOLS
ToolNumberNameUse
MB991502MUT-II sub
assemblyMPI system inspection
MB991348Test harness setMeasurement of voltage during trouble-
shooting
Inspection using an oscilloscope
MB991519Alternator harness
connectorMeasurement of voltage during
troubleshooting
MD998478Test harness
(3-pin, triangle)Measurement of voltage during trouble-
shooting
Inspection using an oscilloscope
Red harness
White harness
MB991223Inspection test
harness set
Pin contact
pressure
inspection
harness
Market tester
contact probe
(for general
connectors)Measurement of terminal voltage
MB991529Diagnostic trouble
code check har-
nessReading of diagnosis codes
MB991709Test harnessMeasurement of voltage during trouble-
shooting
Inspection using an oscilloscope
MPI – Troubleshooting13-7
FAIL-SAFE FUNCTION REFERENCE TABLE
When the main sensor malfunctions are detected by the diagnosis function, the vehicle is controlled
by means of the pre-set control logic to maintain safe conditions for driving.
Malfunctioning itemControl contents during malfunction
Air flow sensor1. Uses the throttle position sensor signal and engine speed signal (crank angle sensor
signal) to take reading of the basic injector drive time and basic ignition timing from
the pre-set mapping.
2. Fixes the ISC servo in the appointed position so idle control is not performed.
Intake air temperature
sensorControls as if the intake air temperature is 25C.
Throttle position
sensorNo increase in fuel injection amount during acceleration due to the throttle position sensor
signal.
Engine coolant
temperature sensor1. Controls as if the engine coolant temperature is 80C.
(This condition is maintained until the ignition switch is turned off even when the
sensor signal returns normal.)
2. Lets the fan motor (radiator and condenser) run at high speed.
Camshaft position
sensorInjects fuel to all cylinders simultaneously for 4 seconds.
(However, after the ignition switch is turned to ON, the No. 1 cylinder top dead centre is not
detected at all.)
Barometric pressure
sensorControls as if the barometric pressure is 101 kPa.
Detonation sensorSwitches the ignition timing from ignition timing for super petrol to ignition timing for standard
petrol.
Ignition coil, power
transistor unitCuts off the fuel supply to cylinders with an abnormal ignition.
Alternator FR terminalDoes not control the output of the alternator according to an electrical load. (works as a
normal alternator)
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 – Troubleshooting13-17
Code No. 64 Alternator FR terminal systemProbable cause
Range of Check
Engine speed is approx. 50 r/min or more
Set Conditions
The input voltage from the alternator FR terminal is higher than 4.5 V for 20 seconds.Open circuit in alternator FR terminal circuit
Malfunction of the engine-ECU
Measure at the alternator connector A-05.
Connect the connector. (Use the test harness: MB991519.)
Voltage between 4 (blue clip) and earth
(Engine: Idling)
(Radiator fan: Stopped)
(Headlamp: OFF → ON)
(Brake lamp: OFF → ON)
(Rear window defogger switch: OFF → ON)
OK:Voltage drops 0.2 to 3.5 VOKReplace the engine-ECU.
NG
Measure at the alternator connector A-05.
Disconnect the connector, and measure at the harness side.
Voltage between 4 and earth
(Ignition switch: ON)
OK:4.8 – 5.2 VNGCheck the following
connectors: B-60, A-88NG
Repair
OK
Check trouble symptom.
NG
Check the harness wire
between the engine-ECU
and the alternator con-
nector.NG
Repair
OK
Replace the engine-ECU.
OK
Check the following connector: A-05NG
Repair
OK
Check trouble symptom.
NG
Check the harness wire between the engine-ECU and the alternator
connector.NG
Repair
OK
Replace the alternator.
MPI – Troubleshooting13-18
INSPECTION CHART FOR TROUBLE SYMPTOMS
Trouble symptomInspection
procedure
No.Reference page
Communication
with MUT-IIis
Communication with all systems is impossible.113-20
with MUT-II is
impossible.
Communication with engine-ECU only is impossible.213-20
Engine warning
lamp and
related parts
The engine warning lamp does not illuminate right after the
ignition switch is turned to the ON position.313-21
related partsThe engine warning lamp remains illuminating and never goes
out.413-21
StartingNo initial combustion (starting impossible)513-22
Initial combustion but no complete combustion
(starting impossible)613-23
Long time to start (improper starting)713-24
Idling stability
(Improper idling)
Unstable idling (Rough idling, hunting)813-25
(Improper idling)
Idling speed is high. (Improper idling speed)913-26
Idling speed is low. (Improper idling speed)1013-27
Idling stability
(Engine stalls)
When the engine is cold, it stalls at idling. (Die out)1113-28
(Engine stalls)
When the engine is hot, it stalls at idling. (Die out)1213-29
The engine stalls when starting the car. (Pass out)1313-30
The engine stalls when decelerating.1413-30
DrivingHesitation, sag or stumble1513-31
The feeling of impact or vibration when accelerating1613-31
The feeling of impact or vibration when decelerating1713-32
Poor acceleration1813-32
Surge1913-33
Knocking2013-33
Dieseling2113-33
Too high CO and HC concentration when idling2213-34
Low alternator output voltage (approx. 12.3 V)2313-35
MPI – Troubleshooting13-35
INSPECTION PROCEDURE 23
Low alternator output voltage (approx. 12.3 V)
Probable cause
The alternator may be defective, or malfunctions, which are listed in the right column,
may be suspected.Malfunction of charging system
Short circuit in harness between alternator G terminal
and engine-ECU
Malfunction of engine-ECU
Measure at the alternator connector
side. A-05
Connect the connector.
(Test harness: MB991519)
Voltage between 1 (black clip) and
earth
Engine: at idle
Radiator fan: does not run
Headlamp: OFF → ON
Brake lamp: OFF → ON
Rear defogger switch:
OFF → ON
OK:Voltages rises
by 0.2 – 3.5 V.NGMeasure at the alternator connector.
A-05
Disconnect the connector, and
measure at the harness side.
Disconnect the engine-ECU con-
nector.
Continuity between 1 and earth
OK:No continuityNGCheck the harness wire between the
alternator and the engine-ECU connec-
tor, and repair if necessary.
OK
Check the alternator.
OK
Check the harness wire between the
alternator and the engine-ECU connec-
tor.NG
Repair
OK
Replace the engine-ECU.
INSPECTION PROCEDURE 24
Power supply system and ignition switch-IG system
Probable cause
When an ignition switch ON signal is input to the engine-ECU, the engine-ECU turns
the control relay ON. This causes system voltage to be supplied to the engine-ECU,
injectors and air flow sensor.Malfunction of the ignition switch
Malfunction of the control relay
Improper connector contact, open or short-circuited
harness wire
Disconnected engine-ECU earth wire
Malfunction of the engine-ECU
Check the control relay. (Refer to P.13-68.)NG
Replace
OK
Measure at the control relay connector B-27.
Disconnect the connector, and measure at the harness side.
Voltage between 3, 4 and earth
OK:System voltageNGCheck the following
connector: A-28NG
Repair
OK
Check trouble symptom.
NG
Check the harness wire between battery and control relay connector,
and repair if necessary.
OK
Check the engine-ECU power supply and earth circuit.
(Refer to P.13-53, INSPECTION PROCEDURE 45.)
MPI – Troubleshooting13-64
Terminal
No.Normal condition Check condition (Engine condition) Check item
20Radiator fan motor
relay (HI)
Radiator fan not operating (coolant temperature:
95C or below)System voltage
105C or above)0 – 3 V
21Fan motor relay (LOW)
below)System voltage
Fan at low speed (coolant temperature: 95 – 100C)0 – 3 V
21Radiator fan motor
relay (LOW)
Radiator fan not operating (coolant temperature:
95C or below)System voltage
– 105C)0 – 3 V
22A/C relayEngine: Idling
A/C switch: OFF to ON (Compressor is being
driven.)System voltage, or 6
V or more instanta-
neously to 0 – 3 V
32A/C condenser fan
motor relay (HI)
A/C condenser fan not operating (A/C switch: ON,
coolant temperature: 105C or below)System voltage
coolant temperature: 105C or above)0 – 3 V
33Alternator G terminalEngine: Warm, idle (radiator fan: OFF)
Headlamp: OFF to ON
Brake lamp: OFF to ON
Rear defogger switch: OFF to ONVoltage rises by 0.2 –
3.5 V.
34A/C condenser fan
motor relay (LOW)
A/C condenser fan not operating (A/C switch: OFF,
coolant temperature: 105C or below)System voltage
coolant temperature: 105C or above)0 – 3 V
36Engine warning lampIgnition switch: OFF → ON0 – 3 V → System
voltage (After several
seconds have
elapsed)
37Power steering fluid
pressure switchEngine: Idling after
warming upWhen steering wheel is
stationarySystem voltage
When steering wheel is
turned0 – 3 V
38Control relayIgnition switch: OFFSystem voltage
Ignition switch: ON0 – 3 V
39Fuel pump relay No.2While engine is idling, suddenly depress the
accelerator pedal.Momentarily rises
slightly from 0 to 3 V.
40Exhaust temperature
warning lampIgnition switch: OFF to ON0 – 3 V to system
voltage (After several
seconds have
elapsed)