Where is the ect sensor on a 1995 toyota previa

The Engine Coolant Temperature Sensor is located in the coolant pipe, below the air intake pipe and behind the right cylinder head and is integral with the ECT sensor. The Engine Coolant Temperature Sensor is located on the back of the right cylinder head and is integral with the ECT sensor.
https://www.autozone.com/repairguides/Audi-Cars-1999-05/Component-Locations/Engine-Coolant-Temperature-ECT-Sensor/_/P-0900c152801c0f85

on the transmission

EOBD II Error Code: P0117
Fault Location:
Engine Coolant Temperature (ECT) Sensor (G62) - Low Input
Possible Cause:
Malfunction Indicator Lamp (MIL) Triggered on first occurrence.
Coolant thermostat.
Wiring short to earth.
Engine coolant temperature (ECT) sensor.

EOBD II Error Code: P0340
Fault Location:
Camshaft Position (CMP) Sensor A (G40), Bank 1 - Circuit Malfunction
Possible Cause:
Malfunction Indicator Lamp (MIL) active.
Wiring from/to Camshaft Position Sensor (CMP) faulty.
Camshaft position (CMP) sensor faulty.
Timing misaligned.
Possible Solutions:
Check Wiring from/to Camshaft Position Sensor.
Check Camshaft Position Sensor.
Check Timing.

EOBD II Error Code: P0500
Fault Location:
Vehicle Speed Sensor (VSS) - Circuit Malfunction
Possible Cause:
Malfunction Indicator Lamp (MIL) Non Emission Fault - No warning light.
Wiring.
Vehicle speed sensor (VSS).
Engine control module (ECM).

EOBD II Error Code: P0117
Fault Location:
Engine Coolant Temperature (ECT) Sensor - Low Input
Possible Cause:
Malfunction Indicator Lamp (MIL) Triggered on first occurrence.
Coolant thermostat.
Wiring short to earth.
Engine coolant temperature (ECT) sensor.

See here p68, p222, p282, p329

http://www.turboninjas.com/camry/eg2.pdf

P0125 TOYOTA - Insufficient Coolant Temperature for Closed Loop Fuel Control

Possible causes- Low engine coolant level
- Leaking or stuck open thermostat
- Faulty Engine Coolant Temperature (ECT) sensor
- Engine Coolant Temperature (ECT) sensor harness is open or shorted
- Engine Coolant Temperature (ECT) sensor electrical circuit poor connection

Automobiles: 2000 Ford Escort ZX2 4-cylinder 2.0L MFI DOHC

NOTE
The "left" side of the engine is the driver's side.

The Engine Coolant Temperature (ECT) sensor is a thermistor (a device which changes resistance or voltage as temperature changes). The sensor detects the temperature of engine coolant and provides a corresponding signal to the PCM (Powertrain Control Module - aka "the car's computer").

The ECT sensor is mounted in the following locations (small Ford engines):

1.8L engines: in the cylinder head
1.9L engines: threaded into the heater hose inlet pipe
2.0L engines: at the left rear of the engine

2.0L Zetec Engine

(1) Partially drain the engine cooling system using a clean container. If coolant is in good condition, retain for reuse.
(2) Disconnect the battery ground cable.
(3) Disconnect the electrical wiring connector from the engine coolant temperature (ECT) sensor.
(4) Remove the retaining clip and the ECT sensor.




Fig. 1 Escort ZX2 ECT sensor - The retaining clip is removed (at the solid arrow). Withdraw ECT sensor by gently wiggling/pulling in the direction of the dashed arrow.

To install:

NOTE
Coat the ECT sensor O-ring with clean coolant prior to installation.

(1) Replace the retaining clip and the ECT sensor.
(2) Connect the electrical wiring connector from the Engine Coolant Temperature (ECT) sensor.
(3) Connect the battery ground cable.
(4) Refill the engine cooling system. An inexpensive plastic "Radiator Funnel" will help with this task.

sounds like it needs a good tune up and new airfilter will sort it out

The ECT (Engine Coolant Temp sensor) should be located by the coolant thermostat housing or where the upper radiator hose connects to the engine. It screws in with a plug or small/short wire harness attached to it. -------------------------------- To replace ect sensor:---

1. Drain and recycle the engine coolant.
2. Remove the intake manifold cover, if necessary.
3. Remove the exhaust crossover.
4. Disconnect the Engine Coolant Temperature (ECT) sensor electrical connector.
5. Remove the ECT sensor.

see fig below:---

.Thanks.

4.2L Engine To Remove:

1. Disconnect the negative battery cable from the battery.
2. Drain the coolant from the engine.
3. Disconnect the engine coolant temperature (ECT) sensor connector. Engine coolant temperature sensor removal and installation
   
   
4. Remove the engine coolant temperature (ECT) sensor from the engine.

To Install:

1. Apply thread sealer P/N 12346004 or equivalent to the engine coolant temperature (ECT) sensor threads.
2. Install the engine coolant temperature (ECT) sensor into the engine. Torque the sensor to 12 ft-lb (16 Nm).
3. Connect the engine coolant temperature (ECT) sensor connector.
4. Refill the engine with coolant.
5. Connect the negative battery cable to the battery.

5.3L & 6.0L Engines To Remove:

1. Drain the coolant from the engine.
2. Disconnect the engine coolant temperature (ECT) sensor connector. Engine coolant temperature sensor removal and installation
   
   
3. Remove the engine coolant temperature (ECT) sensor from the left cylinder head.

To Install:

1. Apply thread sealer P/N 12346004 or equivalent to the engine coolant temperature (ECT) sensor threads.
2. Install the engine coolant temperature (ECT) sensor into the left cylinder head. Torque the sensor to 15 ft-lb (20 Nm).
3. Connect the engine coolant temperature (ECT) sensor connector.
4. Refill the engine with coolant.