sam12345

iTrader: (1)

Does the gauge in the instrument panel use the coolant temperature sensor? If not is there another sensor and where is it located?

This is on a 1998 gs400

AYEmike

it uses the etc sensor but its the one with one wire, its right near the default etc sensor thats for the ecu (which has two wire). so there's two different sensor, one for ecu and one for the gauge, should be in on the passenger side intake manifold right after you remove the engine cover.

sam12345

iTrader: (1)

I only see one sensor in that area any pics?

The only one I see is the one on post #60 on this link

https://www.clublexus.com/forums/gs-...roblems-4.html

The one cicled in red

Here is another image from Sewell which one is it? I only see the coolant one

http://lexus.sewellparts.com/oem-cat...S400-1998.html

sam12345

iTrader: (1)

I looked at the description of every sensor on this car , 50 of them, and there seems to be only one water temperature sensor so I am guessing it uses the same sensor for the ecu and the gauges (the one circled in red in previous post in the link)

Is this a correct conclusion?

99 GS3

iTrader: (14)

There is also a sensor at the bottom of the radiator.

99 GS3

iTrader: (14)

I'm not sure why it doesn't show up on either diagram, it must be listed under another section on their site. But if you go look at your car it is easy to see right down there on the driver side directly beside the draincock (draincock is 16400B in the first diagram)...

This is the temp sensor that feeds the gauge, the one in the waterneck feeds the ecu.

sam12345

iTrader: (1)

That makes no sense to me. The radiator has a totally different temp than the engine. I think that is for the radiator fans.

sam12345

iTrader: (1)

The answer is that the gauge uses the same sensor as the computer.

repugnante

According to that diagram, which one if the temp sensor that feeds the gauge?

sam12345

iTrader: (1)

If you mean the picture above its not in there if you go to the link I posted its there. The sensor sends the temperature to the ECU and the ECU sends appropriate voltage to the guage. Its called a ECT (engine coolant temp sensor).

89422 8942230030
SENSOR, WATER TEMPERATURE (FOR EFI - ELECTRONIC FUEL INJECTION) 01 In Stock $78.88 $65.60

http://lexus.sewellparts.com/oem-cat...S400-1998.html

You can get a chinese version at autozone for 20 bucks

If you look for the shop manual I posted you can see how to trouble shoot it

repugnante

From my experience, most cars have two. One for the guage and one for the ECU. I'm guessing the GS has one for both?

sam12345

iTrader: (1)

Yes thats correct

sam12345

iTrader: (1)

INSPECTION
1. INSPECT COMBINATION METER CIRCUIT
Connector disconnected:
Disconnect connector ”A” and ”B” from the combination meter
and inspect the connectors on the wire harness side as shown
in the table.
Tester connection Condition Specified condition
A1 – Ground Ignition switch ON Battery positive voltage
A3 – A4 Constant Continuity
A7 – Ground
Light control switch HEAD and headlight dimmer
switch HI
Continuity
A8 – Ground
B22 – Ground
Constant Continuity
A10 – Ground Window washer level warning switch Float down Continuity
B1 – Ground Ignition switch ON Battery positive voltage
B4 – B6 Constant Approx. 10 kW
B13 – Ground Constant Battery positive voltage
B14 – Ground Constant Battery positive voltage
B15 – Ground Light control switch in HEAD Battery positive voltage
If circuit is not as specified, wiring diagram and inspect the circuits
connected to other parts.
I04079
Connector ”C” Connector ”D”
Connector ”E” Connector ”F”
Connector ”G”
13 1 13 1
20 1 12 1
BODY ELECTRICAL – COMBINATION METER
BE–93
Author: Date: 2394
2000 LEXUS GS300/GS400 (RM718U)
2. INSPECT COMBINATION METER CIRCUIT PLATE
Warning light circuit plate:
(a) Remove meter cover.
(b) Disconnect connectors ”C”, ”D”, ”E”, ”F” and ”G” from the
meter circuit plate and inspect the connectors on the wire
harness side as shown in the table.
Tester connection Check indicator light Specified condition
D10 (+) – D12 (–) Fuel level warning light Continuity
D6 (+) – D8 (–)
Headlight indiactor light (USA)
Taillight indiactor light (CANADA)
Continuity
D2 (+) – D4 (–) Hi–beam indicator light Continuity
C3 (+) – C7 (–) Engine oil level warning light Continuity
C3 (+) – C5 (–) Malfunction indicator light Continuity
E19 (–) – E20 (+) Slip warning light Continuity
E18 (–) – E20 (+) TRAC OFF indicator light Continuity
E17 (–) – E20 (+) Window washer level warning light Continuity
E16 (–) – E20 (+) ABS warning light Continuity
E15 (–) – E20 (+) VSC OFF indicator light Continuity
E14 (–) – E20 (+) Brake warning light Continuity
E13 (–) – E20 (+) ECT SNOW indicator light Continuity
E12 (–) – E20 (+) Low oil pressure warning light Continuity
E11 (–) – E20 (+) ECT PWR indicator light Continuity
E10 (–) – E20 (+) Discharge warning light Continuity
E9 (–) – E20 (+) CRUISE MAIN indicator light Continuity
E8 (–) – E20 (+) Seat belt warning light Continuity
E7 (–) – E20 (+) Rear Lights warning light Continuity
E6 (–) – E20 (+) Headlight leveling indiactor Continuity
E4 (+) – E5 (–) SRS warning light Continuity
E3 (–) – E4 (+) Open door warning light Continuity
F4 (–) – F12 (+) A/T shift indicator light (L) Continuity
F11 (–) – F12 (+) A/T shift indicator light (2) Continuity
F10 (–) – F12 (+) A/T shift indicator light (3) Continuity
F8 (–) – F12 (+) A/T shift indicator light (P) Continuity
I04080
Connector
”O”, ”P”, ”Q”, ”R”
BE–94
BODY ELECTRICAL – COMBINATION METER
Author: Date: 2395
2000 LEXUS GS300/GS400 (RM718U)
F5 (–) – F12 (+) A/T shift indicator light (R) Continuity
F2 (–) – F12 (+) A/T shift indicator light (N) Continuity
F1 (–) – F12 (+) A/T shift indicator light (D) Continuity
G1 (+) – G5 (–) Left turn signal indicator light Continuity
G6 (+) – G5 (–) Right turn signal indicator light Continuity
If circuit is not as specified, replace the bulb or circuit plate.
3. INSPECT COMBINATION METER CIRCUIT PLATE
From combination meter ECU to gauges:
Terminal Resistance (W)
O1 – O3
(Engine coolant temperature receiver gauge)
Approx. 164.2
O2 – O4
(Engine coolant temperature receiver gauge)
Approx. 151.8
P1 – P4 (Tachometer) Approx. 164.2
P2 – P3 (Tachometer) Approx. 151.8
Q1 – Q4 (Speedometer) Approx. 164.2
Q2 – Q3 (Speedometer) Approx. 151.8
R1 – R4 (Fuel receiver gauge) Approx. 164.2
R2 – R3 (Fuel receiver gauge) Approx. 151.8
If circuit is not as specified, inspect the gauge or meter.
Then recheck system.
If circuit is not as specified, replace the circuit plate.

sam12345

iTrader: (1)

15. INSPECT ENGINE COOLANT TEMPERATURE RECEIVER
GAUGE RESISTANCE
Measure the resistance between terminals with fixing pointer to
the stopper.
Tester connection Resistance (W)
A – B 140 – 185
C – D 130 – 175
If resistance value is not as specified, replace the receiver
gauge.
HINT:
This circuit includes the diode.
If resistance value is not as specified, replace the receiver
gauge.

sam12345

iTrader: (1)

and if that don't work you can always go flying