Cooling fan stays at one slow speed as engine heats up fans never kick up speed to cool engine causing overheating I was told there was a relay under dash but I can't find it on this 1999 lexus es300

if the scan tool ECT sensors show 180f to 200f it is not overheating
what are you talking about.
blower dash fan.
engine RAD fans < guess only this.
or front AC condenser fans.
overheats parked
overheats driving yes or now fast?
oveheats only AC on, none of this told an matters HUGE.
learn to use a scan tool?
you can not fix any modern car lacking one. $100 buy one.
here are the proofs of over heating. al or most.!!!
dash gauge pegs, see that can be coolant low, easy no>?
scan ECT shows temps way over 200F, 265 is boiling point.
coolant on the ground AF 50% green,yellow orange pink what eva.
coolant on the passengers toes(foot well heater core leaks)
coolant in oil pan , and dip stick end drips, chocolate milk.
engine pings, or under load (hills) dont let it. pings is too hot. or dead EGR.
huge engine power loss from ping. (and lots more)
engine guts make huge nasty metallic sounds. bad that. check oil levels.
dash gauge engine heat PEGs , can mean overheating.
dash gauge tad high is normal. z(operators guide said so)

the service manual tells you clear as day what temps trip the fans on if you just RTM/ 214 to 220f , if ECT show that the fans run in that range and lacking a scan tool you will NEVER KNOW IT.
'the dash gauges is NOT and instrument it is a just a crude, toy gauge, the ECT is what matters period. or IR thermal gun pointed to thermostat housing then to top and bottom RAD tanks,


this magic tool and skills I can find dead RAD tubes in 1min flat
love mine, Have 2.

shows 170 here, or 180f if drive 5 miles. your car is 200f stat
a parting shot
no 19 year old thermostat run that long.
the top usa maker claims a 7 year design life
I bet yours is bad. as the wax pellet ages in it ,it shrinks and the TEMPS go way way too high, or are sluggish.
seen it vast times and is frankly normal service.

My information shows that the 2001 tahoe uses a fan clutch and does not any electric fan. There could be exceptions, but if this is an add on aftermarket fan, there would be some type switch with a relay or fuse wired in the system. First make sure that the radiator is not partly restricted. Using a inferred thermometer check to see is all the radiator tubes are the same temp. Most of the time, the lower tubes are cooler because they are restricted. Also make sure the fan clutch is good. After driving it and the engine is at running, shut the engine off and watch how many times the fan rotated. It should stop after several revolutions.

This could be a few things. Check the fuse and relay for the fan. They will be in the fuse box under the hood.
Check the wire connectors to the fan. They could be dirty or corroded. If you can disconnect this connector you could apply a 12 volt supply directly to the fan to see if it 'kicks in'.
If these are OK. It might be the sensor that trips the fans on and off. That will be located on or near the thermostat housing.
If your engine is running hot it could be a faulty thermostat not operating the sensor correctly.
Running a vehicle with no cooling fans isn't a good idea as it'll overheat, cook the engine and cost you serious money to fix.
**If your are in any doubt get a Good mechanic to look at it. Most mechanics won't charge to check a vehicle.**

Usually a bad relay. See this post on GM relays and cooling fans

https://ricksfreeautorepairadvice.com/car-overheating/

What makes you thing it's a sensor ? A lot of thing's could cause this , taking the vehicle to a qualified repair shop is what should be done. They will do a full system scan .
ENGINE HOT A/C OFF
Cooling System Description and Operation

Coolant Warning Messages
The radio will display the following messages if the following conditions exist in the cooling system.
• Engine hot--A/C OFF will be displayed if coolant temperature is above 117°C (243°F). For imports 115°C (239°F).
• Engine coolant hot--Idle engine will be displayed if coolant temperature is above 118°C (245°F).
• Engine overheated--Stop engine will be displayed if coolant temperature is above 123°C (253°F).

Cooling Fan Control - Two Fan System
The engine cooling fan system consists of 2 puller type electrical cooling fans and 3 fan relays. The relays are arranged in a series parallel (S/P) configuration that allows the engine control module (ECM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood fuse block. The ground path is provided at G104.
During low speed operation, the ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the low speed fan relay coil, closes the relay contacts, and supplies battery positive voltage from the low fan fuse through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan S/P relay and the right cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. After a 3 second delay, the ECM supplies a ground path for the high speed fan relay and the cooling fan S/P relay through the high speed cooling fan relay control circuit. This energizes the cooling fan S/P relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time, the high speed fan relay coil is energized closing the relay contacts, and provides battery positive voltage from the high fan fuse on the cooling fan motor supply voltage circuit, to the right cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans running at high speed.
The ECM commands the low speed cooling fans ON under the following conditions:
• Engine coolant temperature exceeds approximately 94.5°C (202°F).
• A/C refrigerant pressure exceeds 1447 kPa (210 psi).
• After the vehicle is shut OFF, if the engine coolant temperature at key-off is greater than 101°C (214°F), the low speed fans will run for a minimum of 60 seconds. After 60 seconds, if the coolant temperature drops below 101°C (214°F), the fans will shut OFF. The fans will automatically shut OFF after 3 minutes, regardless of coolant temperature.
The ECM commands the high speed fans ON under the following conditions:
• Engine coolant temperature exceeds approximately 104.25°C (220°F).
• A/C refrigerant pressure exceeds approximately 1824 kPa (265 psi).
• When certain DTCs set
At idle and very low vehicle speeds the cooling fans are only allowed to increase in speed, if required. This ensures idle stability by preventing the fans from cycling between high and low speed.

DTC P1258: Engine Coolant Overtemperature - Protection Mode Active

Are the cooling fans coming on ? What relay switch did you replace ?
The BCM will request low speed cooling fan operation from the PCM under the following conditions:
?€¢
Engine coolant temperature exceeds approximately 103?°C (217?°F).

?€¢
When A/C is requested and the ambient temperature is more than 10?°C (50?°F).

?€¢
A/C refrigerant pressure exceeds 1310 kPa (190 psi).

?€¢
After the vehicle is shut off if the engine coolant temperature at key-off is more than 117?°C (243?°F) and system voltage is more than 12 volts. The fans will stay on for approximately 3 minutes.

The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the PCM to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the engine wiring harness junction block. The ground path is provided at G101.
During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the FAN CONT #1 relay coil, closes the relay contacts, and supplies battery positive voltage from the FAN CONT #1 fuse through the cooling fan motor supply voltage circuit to the right cooling fan. The ground path for the right cooling fan is through the FAN CONT #2 relay and the left cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the PCM supplies the ground path for the FAN CONT #1 relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the FAN CONT #2 relay and the FAN CONT #3 relay through the high speed cooling fan relay control circuit. This energizes the FAN CONT #2 relay coil, closes the relay contacts, and provides a ground path for the right cooling fan. At the same time the FAN CONT #3 relay coil is energized closing the relay contacts and provides battery positive voltage from the FAN CONT #2 fuse on the cooling fan motor supply voltage circuit to the left cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.
Is your vehicles check engine light lit ?
Is the

The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood accessory wiring junction block. The ground path is provided at G113. The relays are located in the underhood fuse / relay box .
So ,what's the problem Paul , car overheating ? Fans not working ?
During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the cooling fan 1 relay coil, closes the relay contacts, and supplies battery positive voltage from the cool fan 1 fuse through the cooling fan motor supply voltage circuit to the right cooling fan. The ground path for the right cooling fan is through the cooling fan 2 relay and the left cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the PCM supplies the ground path for the cooling fan 1 relay through the low speed cooling fan relay control circuit. After a 3-second delay, the PCM supplies a ground path for the cooling fan 2 relay and the cooling fan 3 relay through the high speed cooling fan relay control circuit. This energizes the cooling fan 2 relay coil, closes the relay contacts, and provides a ground path for the right cooling fan. At the same time the cooling fan 3 relay coil is energized closing the relay contacts and provides battery positive voltage from the cool fan 2 fuse on the cooling fan motor supply voltage circuit to the left cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.
The PCM commands Low Speed Fans on under the following conditions:
?€¢
Engine coolant temperature exceeds approximately 106?°C (223?°F).

?€¢
When the A/C is requested and the ambient temperature is more than 50?°C (122?°F).

?€¢
A/C refrigerant pressure exceeds 1310 kPa (190 psi).

?€¢
After the vehicle is shut off if the engine coolant temperature at key-off is greater than 140?°C (284?°F) and system voltage is more than 12 volts. The fans will stay on for approximately 3 minutes.

The PCM commands High Speed Fans on under the following conditions:
?€¢
Engine coolant temperature reaches 110?°C (230?°F).

?€¢
A/C refrigerant pressure exceeds 1655 kPa (240 psi).

?€¢
When certain DTCs set.

So

Are you talking about the radiator fan? How hot does the engine get in degrees F? Some makes and models, the radiator fan won't turn on till about 220 degrees F. Check for applicable trouble codes, see if any code that refers to the radiator fan circuit or coolant temp sensor? Some of the national brand auto stores will check codes for free.

Of course, as far as overheating in general, you have the thermostat--water pump and other possible issues. Are you losing coolant?

Cars usually overheat when the thermostat is faulty, coolant level is low, or the water pump fails. If your cooling fan on the radiator does not kick on shortly after the engine reaches operating temperature, you may have a bad cooling fan, cooling fan relay, or cooling fan fuse. If your engine is overheating, start by checking the fluid level, and installing a new thermostat.

A blower motor resistor is the device that controls a car's cabin heating and air conditioning unit's fan speeds. This usually won't cause the engine to overheat, your A/C fan may not function or only function at one speed. Here is a Blower Motor Resistor from Autozone: http://www.autozone.com/autozone/parts/2003-Ford-Focus/A-C-Heater-Blower-Motor-Resistor/_/N-jk8uvZ91tag

I’m happy to help further over the phone at https://www.6ya.com/expert/jeremy_69f3cc28d95bf514

At idling speed an engine does build up a lot of heat and the cooling fan will kick in. In slow moving traffic or traffic jams the temperature gauge can touch the red - particularly on hot days. The reason it cools down when you start moving is because of the air flow through the radiator.

Presumably there are no leaks from the cooling system otherwise you would have mentioned it. In normal circumstances the fan will not be running as you are driving at speed, as the air-flow through the radiator is sufficient to cool things. The fan only kicks in to get rid of excess heat - and this usually occurs at idling speed or after you have parked the car.

If the fan is running all the time as you drive, this points to either a fault in the fan switch, or the car is running too hot. presumably in normal driving the fan isn't running and the temperature gauge reads normal?

It is common - in stationary traffic many cars overheat (particularly big engined models) try to stall and 'cut out'. Restarting can be difficult until the engine cools down.

Is your car overheating in normal driving conditions or just at idle speed? Overheating in normal driving conditions can be caused by things like a failing water pump, blocked radiator, collapsed hose, faulty thermostat or, in the worst case scenario, cylinder head problems.

Overheating at idling speed is 'common'. Check your coolant level. If your car isn't using/losing coolant then there probably is no major problem. You can flush out the cooling system and refill with new coolant - and also check your radiator. Are the cooling fins crumbling with age? Or maybe they're partly clogged with insects and debris from the road? A blast with a hosepipe wil sort that out ..

The question is how much does your car overheat in normal driving? If it doesn't .. it appears as though you have nothing to worry about as such. Most cars have 2 speed fans... the 2nd faster stage kicks in at some point dependant on engine temperature. Perfectly normal.