Lexus RX300 (MCU15). Manual — part 400
I08341
PRE
(+)
(–)
ECM
Low Pressure Cut Side
Reference : High Pressure Cut Side
ON (0V)
196 kPa
OFF (12V)
225 kPa
ON (0V)
2,550 kPa
3,140 kPa
OFF (12V)
I07794
1
2
3
4
Low Pressure Cut Side
Reference : High Pressure Cut Side
ON (continuity)
OFF (continuity)
181 kPa
ON (continuity)
OFF (continuity)
211 kPa
3,140 kPa
2,550 kPa
DI–830
–
DIAGNOSTICS
AIR CONDITIONING SYSTEM
LEXUS RX300 (RM785E)
INSPECTION PROCEDURE
1
Check voltage between terminal PRE of engine and ECT ECU and body ground.
PREPARATION:
Install the manifold gauge set.
CHECK:
(a)
Turn ignition switch ON.
(b)
Check voltage between terminal PRE of engine and ECT
ECU connector and body ground when A/C gas pressure
is changed.
OK:
The voltage changes with gas pressure, as shown in
the diagram below.
OK
Proceed to next circuit inspection shown on
problem symptoms table (See page DI–812).
NG
2
Check pressure switch.
PREPARATION:
Disconnect pressure switch connector.
CHECK:
(a)
Turn ignition switch ON.
(b)
Check continuity between terminals 1 and 4 of pressure
switch when A/C gas pressure is changed.
OK:
The continuity changes with gas pressure as shown
below.
NG
Repair or replace harness or connector.
OK
–
DIAGNOSTICS
AIR CONDITIONING SYSTEM
DI–831
LEXUS RX300 (RM785E)
3
Check harness and connector between engine and ECT ECU and pressure
switch, pressure switch and body ground (See page IN–32).
NG
Repair or replace harness or connector.
OK
4
Check harness and connector between engine and ECT ECU and A/C ECU (Com-
bination meter ECU). (See page IN–32).
NG
Repair or replace harness or connector.
OK
Check and replace engine and ECT ECU.
4
(V)
1
TP
terminal
voltage
0
100 %
(Cool)
(Hot)
Damper opening angle
I08342
A25
Air Mix Control Position Sensor
(Air Mix Control Servomotor)
1
5
3
3
9
6
IF1
G–R
B–R
R–L
3
7
10
S5–1
TP
SG–1
A/C ECU (Combina-
tion meter ECU)
C10
IF1
IF1
G–B
B–Y
B
C10
C10
DI–832
–
DIAGNOSTICS
AIR CONDITIONING SYSTEM
LEXUS RX300 (RM785E)
DTC
B1431/31 Air Mix Damper Position Sensor Circuit
CIRCUIT DESCRIPTION
This sensor detects the position of the air mix damper and
sends the appropriate signals to the A/C ECU (Combination
meter ECU).
The position sensor is built into the air mix damper control ser-
vomotor assembly.
DTC No.
Detection Item
Trouble Area
B1431/31
Short to ground or power source circuit in air mix damper posi-
S Air mix damper position sensor.
S Harness or connector between air mix damper control servo-
B1431/31
Short to ground or ower source circuit in air mix dam er osi
tion sensor circuit.
Harness or connector between air mix dam er control servo
motor assembly and A/C ECU (Combination meter ECU).
S A/C ECU (Combination meter ECU).
WIRING DIAGRAM
DI3G0–03
I08343
TP
SG–1
(–)
(+)
–
DIAGNOSTICS
AIR CONDITIONING SYSTEM
DI–833
LEXUS RX300 (RM785E)
INSPECTION PROCEDURE
HINT:
In case of using the hand–held tester, start the inspection from step1 and in case of not using the hand–held
tester, start from step2.
1
Check air mix damper position using hand–held tester.
PREPARATION:
Connect the hand–held tester to the DLC3.
CHECK:
Check the current position of air mix damper and the target position of air mix damper (Passenger Side).
OK:
The current position and target position are almost similar.
OK
Check and replace A/C ECU (Combination me-
ter ECU).
NG
2
Check voltage between terminals TP and SG–1 of A/C ECU (Combination meter
ECU) connector.
PREPARATION:
Remove A/C ECU with connectors still connected.
CHECK:
(a)
Turn ignition switch ON.
(b)
Change the set temperature to activate the air mix damp-
er control servomotor, and measure the voltage between
terminals TP and SG–1 of A/C ECU connector each time
when the set temperature is changed.
OK:
Set Temperature
Voltage
Max. cool
3.5 – 4.5 V
Max. hot
0.5 – 1.5 V
HINT:
As the set temperature increases, the voltage decreases.
NG
Go to step 3.
Ok
Proceed to next circuit inspection shown on problem symptoms table (See page DI–812). Howev-
er, if DTC B1431/31 displayed, check and replace A/C ECU (Combination meter ECU).
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