MB991910
MB991826MB991955
MB991911
MB991824
MB991827
MB991825
A
B C
D
E F
DO NOT USE
S PECIA L T O OLS
ENGINE COOLING14-4
MB991 955
A: MB9918 24
B: MB991827
C: MB99191 0
D: MB991911
E: MB991825
F: MB991 826
M.U.T. -III su b
assembly
A: Ve hicle
communication
interface (V .C.I.)
B: M.U.T. -III US B
cable
C: M.U.T . -III main
ha rn es s A (V e h i c le s
with CA N
communication
sy stem )
D: M.U.T. -III main
ha rn es s B (V e h i c le s
wit hout CAN
communication
sy stem )
E: M.U.T. -III
measureme n t
ad apter
F: M.U.T . -III trig ger
ha rness
Checkin g the A/T
(D
ia gn osis d i sp lay using t h e
M.U.
T . -III)
MB991223
A
D C
B
AZ
DO NOT USE
MB991 223
A: MB9912 19
B: MB991220
C: MB99122 1
D: MB991222
Harness se t
A: Check h a rnes s
B: LE D ha rness
C: LED ha rness
ad apter
D: Probe
Making vo lt age an d
resist
an ce measureme n t
during tro
uble s hoo ting
A: Connector pin cont act
pressure inspect i on
B: Power circuit inspection
C: Power circuit inspection
D: Commercial tester
con nect i on
Tool Nu mber Na me Use
TROUBLESHOOTING
ENGINE COOLING14-15
STEP 22. Check the cooling fan motor drive
control unit.
AC303555AB
Connector: C-123
or
C-122
C-123
Engine-ECU
engine-A/T-ECU
C-122
(1) D isconn ect e ngin e -ECU conne ctor C-12 3
or e ngine -A/T -ECU conne ctor C-12 2 .
AC303559
C-122 connector
(Harness side connector: ECU side view)
AB
C-123 connector
(Harness side connector: ECU side view)
(2)P ull out conne ctor t e rminal p i n 21
to discon nect conn ector .
(3)R eco nnect t he con necto r with conn ector ter m in al
pin still removed.
(4)T urn t he ig nition switch to the "ON" positio n.
(5)C heck fo r the cooling fan opera t ion.
•The cooling fan ro t a t e s. (with conne ctor termi-
nal pi n 21
•The cooling fan stop s. (When con necto r ter-
minal pi n 21
to the
body earth.)
(6)T urn t he ig nition switch t o the "OFF" po sit i on.
(7)D isconn ect e ngin e -ECU conne ctor C-12 3
or e ngine -A/T -ECU conne ctor C-12 2 , a nd
push in con nect o r terminal pin 21
to discon nect conn ector .
(8)R econnect the con necto r with conn ector te rmin al
pin still inst alled.
Q:Doe s the cooling fa n rot a te ? And wh en th e
c onne ct or te rmin a l p i n is co nnec t e d to t h e bod y
e a rt h, d o es t h e co olin g f a n s t op ?
YES : Go to S t ep 2 3 .
NO : Replac e th e coo lin g fan motor d r ive con t rol
unit (Refer to
P.14-33) <4G1> (Refer to
P.14-35) <4G6>. Then go to S t e p 24 .
STEP 2 3 . M.U.T . -II/III self-dia g code
Check if an MPI system self- d iag code is set. (Ref er
to GROUP
13A - T r ouble shooting
P.13A-9) <4G1>
or (Refer to GROUP 13 B - T r ouble sho o ting
P.13B-9) <4G6>.
Q:Diagn o sis co de se t?
YES : Inspecti on chart fo r dia gnosis code (Re f er
to GROUP 13A - T r ou ble shoot ing
P.13A-15) <4G1 > or Inspection chart for
diagnosis code (Re f er to GROUP 13B -
T
r ouble sh ootin g
P.13B-15) <4G6>.
NO : Replac e th e engine-ECU
engine-A/T
- ECU (Refer to GROUP
13A
P.13A- 384). Then go t o S t ep 24 .
STEP 2 4 . Check t he sym ptoms.
Q:Doe s the cooling fa n moto r ( L .H.) and t h e coo l ing
fa n mo to r ( R .H. ) <4G 1 (V ehicles with A/ C)> or A/C
c onde nse r fa n mo tor <4G6> o p era t e c o rre ct ly ?
YES : This symptoms is comple te.
NO : Return to S t ep 1 .
TROUBLESHOOTING
ENGINE COOLING14-19
(8) Reconnect the connector with connector terminal
pin still installed.
Q: Does the cooling fan rotate? And when the
connector terminal pin is connected to the body
earth, does the cooling fan stop?
YES : Go to Step 7 .
NO : Replace the cooling fan motor drive control
unit (Refer to
P.14-33) <4G1> (Refer to
P.14-35) 4G6>. Then go to Step 8 .
STEP 7. M.U.T.-II/III self-diag code
Check if an MPI system self-diag code is set. (Refer
to GROUP 13A - Trouble shooting
P.13A-9) <4G1>
or (Refer to GROUP 13B - Trouble shooting
P.13B-9) <4G6>.
Q: Diagnosis code set?
YES : Inspection chart for diagnosis code (Refer
to GROUP 13A - Trouble shooting
P.13A-15) <4G1> or Inspection chart for
diagnosis code (Refer to GROUP 13B -
Trouble shooting
P.13B-15) <4G6>.
NO : Replace the engine-ECU
engine-A/T-ECU (Refer to GROUP
13A
P.13A-384). Then go to Step 8 .
STEP 8. Check the symptoms.
Q: Does the cooling fan motor (L.H.) and the cooling
fan motor (R.H.) <4G1 (Vehicles with A/C)> or A/C
condenser fan motor <4G6> operate correctly?
YES : This symptoms is complete.
NO : Return to Step 1 .
INSPECTION PROCEDURE 3: Cooling Fan (L.H.) does not Operate {When Cooling Fan (R.H.) <4G1> or
A/C Condenser Fan <4G6> Operate}
COOLING FAN (L.H.) AND COOLING FAN
(R.H.) OR A/C CONDENSER FAN DRIVE
CIRCUIT
Refer to P.14-6.
CIRCUIT OPERATION
Refer to P.14-6.
TECHNICAL DESCRIPTION
The cause could be a malfunction of the cooling fan
motor (L.H.) or cooling fan motor drive control unit.
TROUBLESHOOTING HINTS
•Malfunction of cooling fan motor (L.H.)
•Malfunction of cooling fan motor drive control unit
DIAGNOSIS
STEP 1. Check the cooling fan motor (L.H.).
Refer to P.14-24.
Q: Is the cooling fan motor (L.H.) in good condition?
YES : Go to Step 2 .
NO : Replace the cooling fan motor (L.H.) (Refer
to
P.14-33) <4G1> (Refer to P.14-35)
<4G6>. Then go to Step 3 .
STEP 2. Check the cooling fan motor drive
control unit.
Refer to P.14-22.
Q: Is the cooling fan motor drive control unit in good
condition?
YES : Go to Step 3 .
NO : Replace the cooling fan motor drive control
unit (Refer to
P.14-33) <4G1> (Refer to
P.14-35) <4G6>. Then go to Step 3 .
STEP 3. Check the symptoms.
Q: Do the cooling fan (L.H.) operate (when the cooling
fan (R.H.) <4G1> or A/C condenser fan <4G6>
operate)?
YES : This symptoms is complete.
NO : Return to Step 1 .
CHARGING SYSTEM
ENGINE ELECTRICAL16-4
2. Turn the ignition switch to the "LOCK" (OFF)
position.
3. Disconnect the negative battery cable.
4. Connect a clamp-type DC test ammeter with a
range of 0
− 120 A to the alternator "B" terminal
output wire.
NOTE: The way of disconnecting the alternator
output wire and of connecting the ammeter is pos
-
sibly not found the problem that the output current
is dropping due to the insufficient connection
between terminal "B" and the output wire.
5. Connect a digital-type voltmeter between the
alternator "B" terminal and the battery (+)
terminal. [Connect the (+) lead of the voltmeter to
the "B" terminal and the connect the (-) lead of the
voltmeter to the battery (+) cable].
6. Reconnect the negative battery cable.
7. Connect a tachometer or the M.U.T.-II/III (Refer to
GROUP 11A
− On-vehicle Service − Idle speed
check <4G1>
P.11A-11 or GROUP 11C −
On-vehicle Service − Idle speed check <4G6>
P.11C-11).
8. Leave the hood open.
9. Start the engine.
10.With the engine running at 2,500 r/min, turn the
headlamps and other lamps on and off to adjust
the alternator load so that the value displayed on
the ammeter is slightly above 30 A.
Adjust the engine speed by gradually decreasing
it until the value displayed on the ammeter is 30
A. Take a reading of the value displayed on the
voltmeter at this time.
Limit: maximum 0.3 V
NOTE: When the alternator output is high and the
value displayed on the ammeter does not
decrease until 30 A, set the value to 40 A. Read
the value displayed on the voltmeter at this time.
When the value range is 40 A, the limit is maxi
-
mum 0.4 V.
11.If the value displayed on the voltmeter is above
the limit value, there is probably a malfunction in
the alternator output wire, so check the wiring
between the alternator "B" terminal and the
battery (+) terminal (including fusible link).
If a terminal is not sufficiently tight or if the
harness has become discolored due to
overheating, repair and then test again.
12.After the test, run the engine at idle.
13.Turn off all lamps and the ignition switch.
14.Remove the tachometer or the M.U.T.-II/III.
15.Disconnect the negative battery cable.
16.Disconnect the ammeter and voltmeter.
17.Connect the negative battery cable.
CHARGING SYSTEM
ENGINE ELECTRICAL16-6
9. Check that the reading on the voltmeter is equal
to the battery voltage.
NOTE: If the voltage is 0 V, the cause is probably
an open circuit in the wire or fusible link between
the alternator "B" terminal and the battery (+) ter
-
minal.
10.Turn the light switch on to turn on headlamps and
then start the engine.
11.Immediately after setting the headlamps to high
beam and turning the heater blower switch to the
high revolution position, increase the engine
speed to 2,500 r/min and read the maximum
current output value displayed on the ammeter.
Limit: 70 % of normal current output
NOTE: .
•For the nominal current output, refer to the
Alternator Specifications.
•Because the current from the battery will soon
drop after the engine is started, the above step
should be carried out as quickly as possible in
order to obtain the maximum current output
value.
•The current output value will depend on the
electrical load and the temperature of the
alternator body.
•If the electrical load is small while testing, the
specified level of current may not be output
even though the alternator is normal. In such
cases, increase the electrical load by leaving
the headlamps turned on for some time to dis
-
charge the battery or by using the lighting sys-
tem in another vehicle, and then test again.
•The specified level of current also may not be
output if the temperature of the alternator body
or the ambient temperature is too high. In such
cases, cool the alternator and then test again.
12.The reading on the ammeter should be above the
limit value. If the reading is below the limit value
and the alternator output wire is normal, remove
the alternator from the engine and check the
alternator.
13.Run the engine at idle after the test.
14.Turn the ignition switch to the "LOCK" (OFF)
position.
15.Remove the tachometer or the M.U.T.-II/III.
16.Disconnect the negative battery cable.
17.Disconnect the ammeter and voltmeter.
18.Connect the negative battery cable.
CHARGING SYSTEM
ENGINE ELECTRICAL16-8
If the voltage is not within the standard value,
there is a malfunction of the voltage regulator or of
the alternator.
14.After the test, lower the engine speed to the idle speed.
15.Turn the ignition switch to the "LOCK" (OFF) position.
16.Remove the tachometer or the M.U.T.-II/III.
17.Disconnect the negative battery cable.
18.Disconnect the ammeter and voltmeter.
19.Connect the alternator output wire to the alternator "B" terminal.
20.Remove the special tool, and return the connector
to the original condition.
21.Connect the negative battery cable.
Voltage Regulation Table
Standard value:
Inspection terminalVoltage regulator ambient
temperature
°C
Voltage V
Terminal "S"−2014.2 − 15.4
2013.9 − 14.9
6013.4 − 14.6
8013.1 − 14.5