Where is the temperature sending switch - 1995 Honda Passport

Have the temperature sending sensor tested. When first starting a cold engine, that is not at operating temperature, when you first turn the switch on to get ready to crank the engine over, automatically the working temperature sensor will send a message telling the computer to place the engine into "cold start mode". If the temp sensor is malfunctioning/broken it won't send this message and the engine is hard to start. Yet, if you feather the throttle a bit for long enough to get the engine warm, it will keep running on it's own. No fun in the wait.

which 2 sensors did you r/r? was one a temperature SENDING switch? Poss gauge ? see if your getting any voltage to the sensors themselves & same w/ sending switch.Electric fans working?

you might have two temperature sensors one turn the fan on the other is called the temperature gauge sending unit if not check your gauge

Either a faulty electric coolant temperature sending switch (if the temperature never gets too hot) or a faulty mechanical thermostat (if the temperature does in fact briefly gets too hot). Good luck!

If the fans work when hooked up directly. this indicates that the fan motors are okay. The next step is to check if the coolant temperature sensor (usually located near the thermostat housing) to see if it sending a signal to the relay when the engine temperature goes above normal. This part is inexpensive and easily replaced; throw one in if you still have the original. A second sensor (or switch) may need to be checked; this is the radiator fan switch. These two usually work as a "team" in managing engine temperatures; one switch tells the computer and the instrument gauge what temperature your engine is operating in, while the other responds by sending a signal to the radiator fan relay to "kick on" the fan.

Lastly, the radiator fan relay itself may have burned out. I usually try to switch out identical relays to determine if this is the problem.


Hope this helps.


Have a Nice Day !!!

the cooling fan will only run when the vehicle reaches a certain temperature around 100 degrees Celsius. it does this using a temperature switch (usually the coolant temp sensor or a temperature switch located on the radiator). the switch sends power to a relay in the engine compartment (should be marked or you can trace the wires from the fan directly to it). the relay, when activated, sends power to the fan. you should be able to figure it out using a test light. check fuses first though. probably a bad temperature switch. if you do not know how to figure out this problem with the information provided you should probably have a technician check it out for you.

the fan comes on and off based on the "temperature sending unit" thats a thermal switch mounted on the radiator .. it is normal for the temperature to fluxuate as the fan turns on and off .. if it is allowed to get too hot before turning on then the temperature sending unit should be replaced ...while the car is moving the fan may never come on and isnt needed as long as air is flowing through the radiator .. as long as you are not loosing coolant then the temperatures are probably within proper range ... a sticking thermostat can also cause increased temperature range fluxuations .. that will show up as large swings of temp while driving .....

Ok, you have three sensors on this engine that work together to manage the temperature reading that are sent to the gauge. i recommend checking all three to be safe. i will list the sensors and, locations below.

1. Coolant temperature sensor- Under hood, driver side, upper engine area, above transmission bell housing, mounted in driver side end of intake manifold.

2. Engine Temperature sensor- Under hood, driver side, upper engine area, mounted on rear cylinder head

3. Temperature switch.- Under hood, center, lower engine area, above oil filter, rear of coolant temperature sensor, mounted in engine block

SECTION 303-14: Electronic Engine Controls 2000 Expedition/Navigator Workshop Manual DESCRIPTION AND OPERATION Electronic Engine Controls The electronic engine controls consist of the:

• powertrain control module (PCM)

• throttle position (TP) sensor

• idle air control (IAC) valve

• engine coolant temperature (ECT) sensor

• camshaft position (CMP) sensor

• crankshaft position (CKP) sensor

• mass air flow (MAF) sensor

• intake air temperature (IAT) sensor

• heated oxygen sensor (HO2S)

• knock sensor (KS)

• vehicle speed sensor (VSS)

• cylinder head temperature (CHT) sensor

The PCM needs the following inputs to calibrate the engine correctly:

• engine rpm

• engine coolant temperature

• amount of engine detonation

• crankshaft position

• air temperature

• throttle position

• cylinder head temperature

• mass air flow

The TP sensor:

• sends the PCM a signal indicating the throttle plate angle.

• is the main input to the PCM from the driver.

The IAC valve:

• controls bypass air around the throttle plate at low speeds.

• is controlled by the PCM.

The ECT sensor:

• sends the PCM a signal indicating engine temperature.

• resistance decreases as coolant temperature increases.

The CMP sensor:

• sends the PCM a signal indicating camshaft position used for fuel synchronization.

The CKP sensor:

• sends the PCM a signal indicating crankshaft position.

• is essential for calculating spark timing

The MAF sensor:

• sends the PCM a signal indicating mass airflow rate of air entering the engine.

The IAT sensor:

• sends the PCM a signal indicating the temperature of the air entering the engine.

• resistance decreases as temperature increases.

The HO2S:

• has the ability to create a voltage signal dependent on exhaust oxygen content.

• provides feedback information to the PCM used to calculate fuel delivery.

The 4.6L KS is located in the lifter valley. The 5.4L has a unique linear KS located in the lifter valley.

• The KS sends a signal to the PCM indicating engine detonation.

The CHT sensor:

• is mounted into the wall of the cylinder head and is not connected to any coolant passages.

• sends a signal to the PCM indicating cylinder head temperature.
  • If the temperature exceeds 126°C (258°F) 5.4L, 130°C (265°F) 4.6L, the PCM disables four fuel injectors at a time. The PCM will alternate which four fuel injectors are disabled every 32 engine cycles. The four cylinders the are not being fuel injected act as air pumps to aid in cooling the engine.
  • If the temperature exceeds 154°C (310°F) 5.4L, 166°C (330°F) 4.6L, the PCM disables all of the fuel injectors until the engine temperature drops below , 154°C (310°F) 5.4L, 153°C (308°F) 4.6L.

The VSS:

• is gear driven by the transmission.

• sends a signal to the PCM indicating vehicle speed. For additional information, refer to Section 307-01A R4100 and/or Section 307-01B 4R70W

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P1151 - Lack of HO2S-21 Switch, Sensor Indicates Lean A HEGO sensor indicating lean at the end of a test is trying to correct for an over-rich condition. The test fails when fuel control system no longer detects switching for a calibrated amount of time. See Possible Causes for DTC P1130

P1130 - Lack of HO2S-11 Switch, Fuel Trim at Limit The HEGO Sensor is monitored for switching. The test fails when the HO2S fails to switch due to circuit or fuel at or exceeding a calibrated limit.

• Electrical:
  • Short to VPWR in harness or HO2S
  • Water in harness connector
  • Open/Shorted HO2S circuit
  • Corrosion or poor mating terminals and wiring
  • Damaged HO2S
  • Damaged PCM
• Fuel System:
  • Excessive fuel pressure
  • Leaking/contaminated fuel injectors
  • Leaking fuel pressure regulator
  • Low fuel pressure or running out of fuel
  • Vapor recovery system
• Induction System:
  • Air leaks after the MAF
  • Vacuum Leaks
  • PCV system
  • Improperly seated engine oil dipstick
• EGR System:
  • Leaking gasket
  • Stuck EGR valve
  • Leaking diaphragm or EVR
• Base Engine:
  • Oil overfill
  • Cam timing
  • Cylinder compression
  • Exhaust leaks before or near the HO2S(s)

A fuel control HO2S PID switching across 0.45 volt from 0.2 to 0.9 volt indicates a normal switching HO2S.

P0153 - HO2S Sensor Circuit Slow Response (HO2S-21) See DTC P0133

P0133 - HO2S Sensor Circuit Slow Response (HO2S-11) The HEGO Monitor checks the HO2S Sensor frequency and amplitude. If during testing the frequency and amplitude were to fall below a calibrated limit, the test will fail.

• Contaminated HO2S sensor.
• Exhaust leaks.
• Shorted /open wiring.
• Improper fueling.
• MAF sensor.
• Deteriorating HO2S sensor.
• Inlet air leaks.

Access HO2S test results from the Generic OBD-II menu to verify DTC.

the temperature sending unit which only controls the gauge is bad it is located on the left of the cylinder head very close to the exhaust manifold, first check and makes sure that rhe wire is not grounding if the wire is ok replace the temperature sending unit