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1) Using ohmmeter, check for continuity between specified
rear differential lock switch terminals with switch in specified
positions. See WIRING DIAGRAMS.
2) With lock switch in ON position, continuity should exist
between terminals No. 2 and 5. With lock switch in OFF position,
continuity should exist between terminals No. 2 and 3.
3) Continuity should also exist between terminals No. 1 and 6
with lock switch in ON or OFF position. If continuity is not as
specified, replace lock switch.
REAR DIFFERENTIAL LOCK SYSTEM AIR LEAKAGE CHECK
NOTE: DO NOT apply more pressure than required to bring pressure
gauge reading to about 5 psi (.35 kg/cm ).
1) Remove rear differential lock air pump and remove air hose
from air pump. Connect a pressure gauge and air regulator (for
adjusting compressed air pressure) to air hose. Using air regulator,
adjust compressed air pressure until pressure gauge indicates about 5
psi (.35 kg/cm
).
2) Shut off air valve. Wait about 10 minutes and check if air
pressure has dropped. If air pressure has dropped, air hose is not
leaking.
REMOVAL & INSTALLATION
REAR DIFFERENTIAL LOCK AIR PUMP
Removal & Installation
Remove rear seat. Remove bracket from rear differential lock
air pump and remove air pump. Disconnect air hoses from air pump.
Disconnect electrical connector from air pump. To install, reverse
removal procedure.
REAR DIFFERENTIAL LOCK CONTROL UNIT
Removal & Installation
Remove left side lower quarter trim panel in rear
compartment. Remove rear differential lock control unit. Disconnect
electrical connector from control unit. To install, reverse removal
procedure.
WIRING DIAGRAMS
Page 394 of 1501
Fig. 3: Rear Differential Lock System Wiring Diagram (1997 Montero)
Page 395 of 1501
Fig. 4: Rear Differential Lock System Wiring Diagram (1998 Montero)
Page 396 of 1501
Fig. 5: Rear Differential Lock System Wiring Diagram (1998
Montero Sport)
Page 399 of 1501

Scan Tool Method (3000GT)
Turn ignition off. Connect scan tool to DLC. Follow scan tool
manufacturer's instructions. Turn ignition on. Perform ON/OFF
operation of each door lock or power window switch. If scan tool
buzzer sounds once, ECU input signal to corresponding switch circuit
is normal.
Voltmeter Method (3000GT)
Using Diagnostic Trouble Code Check Harness (MB991529),
connect harness to DLC terminals No. 4 and 5. Connect voltmeter to
harness. Turn ignition on. Perform ON/OFF operation of each door lock
or power window switch. If voltmeter pointer moves once, ECU input
signal from corresponding switch circuit is normal.
COMPONENT TESTS
* PLEASE READ THIS FIRST *
NOTE: If after all testing procedures are completed, system is not
functioning properly, substitute with a known-good ETACS-ECU
and retest.
DOOR LOCK ACTUATOR
Left Front Door (Montero & 3000GT)
1) Access left front door lock actuator. See
DOOR LOCK ACTUATOR R & I under REMOVAL & INSTALLATION. Disconnect
harness connector. Set actuator in LOCK position. Connect positive
lead of 12-volt power source to actuator terminal No. 1 (Blue/Red
wire) on Montero or terminal No. 3 (Blue/Red wire) on 3000GT. See
WIRING DIAGRAMS . Actuator should move to UNLOCK position when terminal
No. 3 (White/Black wire) on Montero or terminal No. 1 (Blue/Black
wire) on 3000GT is connected to ground.
2) With actuator set in UNLOCK position, connect positive
lead of 12-volt power source to actuator terminal No. 3 (White/Black
wire) on Montero or terminal No. 1 (Blue/Black wire) on 3000GT. See
WIRING DIAGRAMS . Actuator should move to LOCK position when terminal
No. 1 (Blue/Red wire) on Montero or terminal No. 3 (Blue/Red wire) o\
n
3000GT is connected to ground.
3) On 3000GT, check for continuity between actuator terminals
No. 2 (Brown/Yellow wire) and No. 4 (Black wire). See WIRING DIAGRAMS.
Continuity should be present with actuator set in UNLOCK position.
Continuity should not be present with actuator set to LOCK position.
Right Front Door (Montero & 3000GT)
1) Access right front door lock actuator. See
DOOR LOCK ACTUATOR R & I under REMOVAL & INSTALLATION. Disconnect
harness connector. Set actuator in LOCK position. Connect positive
lead of 12-volt power source to actuator terminal No. 3 (Blue/Red
wire) on Montero or terminal No. 1 (Blue/Red wire) on 3000GT. See
WIRING DIAGRAMS . Actuator should move to UNLOCK position when terminal
No. 1 (White/Black wire) on Montero or terminal No. 3 (Blue/Black
wire) on 3000GT is connected to ground.
2) With actuator set in UNLOCK position, connect positive
lead of 12-volt power source to actuator terminal No. 1 (White/Black
wire) on Montero or terminal No. 3 (Blue/Black wire) on 3000GT. See
WIRING DIAGRAMS . Actuator should move to LOCK position when terminal
No. 3 (Blue/Red wire) on Montero or terminal No. 1 (Blue/Red wire) o\
n
3000GT is connected to ground.
3) On 3000GT, check for continuity between actuator terminals
No. 2 (Brown wire) and No. 4 (Black wire). See WIRING DIAGRAMS.
Continuity should be present with actuator set in UNLOCK position.
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Continuity should not be present with actuator set to LOCK position.
Left Rear Door (Montero)
1) Access and disconnect harness from left rear door lock
actuator. See DOOR LOCK ACTUATOR R & I under REMOVAL & INSTALLATION.
Set actuator in LOCK position. Connect positive lead of 12-volt power
source to actuator terminal No. 3 (Blue/Red wire). See WIRING DIAGRAMS
. Actuator should move to UNLOCK position when terminal No. 1
(Blue/Black wire) is connected to ground.
2) With actuator set in UNLOCK position, connect positive
lead of 12-volt power source to actuator terminal No. 1 (Blue/Black
wire). See WIRING DIAGRAMS . Actuator should move to LOCK position when
terminal No. 3 (Blue/Red wire) is connected to ground.
Right Rear Door (Montero)
1) Access and disconnect harness from right rear door lock
actuator. See DOOR LOCK ACTUATOR R & I under REMOVAL & INSTALLATION.
Set actuator in LOCK position. Connect positive lead of 12-volt power
source to actuator terminal No. 1 (Blue/Black wire). See
WIRING DIAGRAMS . Actuator should move to UNLOCK position when terminal
No. 3 (Blue/Red wire) is connected to ground.
2) With actuator set in UNLOCK position, connect positive
lead of 12-volt power source to actuator terminal No. 3 (Blue/Red
wire). See WIRING DIAGRAMS . Actuator should move to LOCK position when
terminal No. 1 (Blue/Black wire) is connected to ground.
DOOR LOCK POWER RELAY
1) Remove door lock relay. See COMPONENT LOCATIONS. Check for
continuity between relay terminals No. 1, 3 and 5, and terminals No.
4, 7 and 8. See RELAY TERMINAL IDENTIFICATION table. Continuity should
be present.
2) Apply positive battery voltage to relay terminal No. 7 and
ground to terminals No. 4 and 8. Check for continuity between relay
terminals No. 1 and 2, and terminals No. 2 and 3. See
RELAY TERMINAL IDENTIFICATION table. Continuity should be present.
Replace relay if continuity is not as specified.
RELAY TERMINAL IDENTIFICATION TABLE
\
\
\
\
\
\
Application & Harness
Terminal No. Wire Color
Montero
1 ........................................... Blue/Green
2 ............................................ Red/White
3 .......................................... Blue/Orange
4 ............................................ Black/Red
5 ................................................ Black
7 ............................................ Red/Black
8 ......................................... Black/Yellow
3000GT (Relays No. 1 & 2)
1 ........................................... Blue/Black
2 ............................................ Red/Black
3 ............................................. Blue/Red
4 .......................................... Brown/White
5 ................................................ Black
7 ............................................ Red/Black
8 ........... Brown/Blue (No. 1) Or Yellow/Black (No. 2)
\
\
\
\
\
\
DOOR LOCK CYLINDER SWITCH
Page 405 of 1501

NOTE: Testing information for RKE control unit is not available
from manufacturer at time of publication. See
PIN VOLTAGE TESTS .
NOTE: If after all testing procedures are completed, system is not
functioning properly, replace unit with a known-good keyless
entry control unit and retest.
POWER DOOR LOCK CONTROL UNIT
Montero (W/O Remote Keyless Entry)
1) Remove power door lock control unit. See
COMPONENT LOCATIONS . Apply battery voltage to control unit terminal
No. 8 (Red/Yellow wire). See WIRING DIAGRAMS.
2) Jumper control unit terminals No. 4 (Black wire), No. 5
(Blue/White wire), and No. 7 (Black/Yellow wire) to battery negative\
terminal. Connect an analog voltmeter between ground and terminal No.
3 (Blue/Red wire). Set voltmeter to DC volts.
3) Remove jumper from control unit terminal No. 5 or 7.
Voltmeter needle should deflect.
4) Jumper control unit terminals No. 4 (Black wire) and No. \
5
(Blue/White wire) to ground. Connect voltmeter between ground and
terminal No. 3 (Blue/Red wire). Jumper control unit terminal No. 7
(Black/Yellow wire) to ground. Voltmeter needle should deflect.
5) Jumper control unit terminal No. 4 (Black wire) to ground\
.
Connect voltmeter between ground and control unit terminal No. 3
(Blue/Red wire). Jumper control unit terminal No. 7 (Black/Yellow
wire) to ground. Voltmeter needle should not deflect.
6) Check if voltage is present between battery ground and
control unit terminals No. 2 (Black/Blue wire) and No. 6 (Black/Red
wire). Battery voltage should be present. If circuits do not test as
specified, replace door lock control unit.
BACK DOOR (LIFTGATE) LOCK ACTUATOR
Montero
Access door lock actuator. See DOOR LOCK ACTUATOR R & I under
REMOVAL & INSTALLATION. Disconnect back door actuator harness
connector. Remove actuator if needed. Connect positive lead of 12-volt
power source to actuator connector. Actuator should operate when
negative lead contacts actuator housing. Replace actuator as needed.
PIN VOLTAGE TESTS
Page 408 of 1501
DOOR LOCK ACTUATOR R & I
Removal & Installation (Except Back Door)
Remove inner door panel. Remove delta cover (access to mirror
mounting). Remove door light, switch panel and armrest. Remove
mounting screws, and slide panel up to remove. Remove waterproof film.
Remove actuator. To install, reverse removal procedure.
Removal & Installation (Back Door)
Remove door pull handle. Remove window trim. Remove door
release handle trim. Remove tool kit (if equipped). Remove door panel
and waterproof film. Remove actuator. To install, reverse removal
procedure.
WIRING DIAGRAMS