Not getting hot sensor temperature - 1993 Geo Tracker

There could be a few different issues that could cause the temperature gauge on your 2008 Ford Focus to read hot when the engine is not actually overheating. Here are a few things to consider:

Failed thermostat: The thermostat is responsible for regulating the flow of coolant through the engine. If the thermostat is stuck in the closed position, it could cause the temperature gauge to read hot even though the engine is not overheating.

Failed temperature sensor: The temperature sensor sends a signal to the temperature gauge to indicate the engine's temperature. If the temperature sensor is faulty, it could cause the temperature gauge to read hot even though the engine is not overheating.

Wiring issue: If there is a problem with the wiring that connects the temperature sensor to the temperature gauge, it could cause the gauge to read hot even though the engine is not overheating.

To determine the cause of the issue, it may be necessary to perform some diagnostic tests and possibly replace some components. A mechanic or a professional auto repair shop will be able to diagnose the problem and recommend the appropriate repairs. It's also a good idea to keep an eye on the engine temperature and take note of any other symptoms or issues you may be experiencing. This information can help the mechanic diagnose the problem more accurately

code p 0442 refers to EVAP system so that is unlikely
check the fan operation and if you have a viscous fan hub ( fan clutch ) replace it
if you have electric fans , check coolant temperature sensor for operation , fuses , relay and fans
overheating is from low coolant levels , head gaskets/cracked heads, blocked radiator cores , fins flaking off core tubes, incorrect timing, blocked exhaust( cat converter)problem thermostat, over loading /over speeding, overdrive not engaging
if you over heating is predominately at lights , slow moving traffic or high engine rpms with low speed --check the fan operation and if it is viscous fan hub driven --replace the hub or if electric fans have that circuit checked out

Its possible that your problem also stay in the Engine Coolant Temperature (ECT) sensor resistance changes in response to engine coolant temperature.

Keep in mindthat the sensor resistance decreases as coolant temperature increases. This provides a reference signal, which indicates engine coolant temperature, to the ECM.





Fig.: Compare the sensor readings with these values




Fig.: Location of the thermal sending unit (A) next to the coolant temperature sensor (B)

Keep us updated.

Check the connectors at the PCM or ECU; lose ones could cause this problem. Something else to consider is to get the sensor from the dealership; many of these sensors are very sensitive and aftermarket ones tend to not be calibrated correctly.

IF COOLANT FAN FUSE AND RELAY OKAY.HOT WIRE COOLANT FAN TO SEE IF FAN MOTOR OKAY.IF FAN MOTOR OKAY.THE ENGINE COOLANT TEMPERATURE SENSOR MORE LIKELY BAD.THE ENGINE COOLANT SENSOR WHEN ENGINE COOLANT GETS HOT IT CAUSES ENGINE COOLANT TEMPERATURE RESISTANCE TO DECREASE CAUSE COMPLETE CIRCUIT IN WHICH POWER FROM PCM TO ECT SENSOR WILL SENT POWER TO COOLANT FAN RELAY THEN CAUSE COOLANT FAN TO TURN ON. HAVE ECT SENSOR OR ENGINE COOLANT TEMPERATURE SENSOR CHECK USING CODE SCANNER TO MAKE SURE ITS WORKING BEFORE SPENDING EXCESS MONEY.

change your temperature sensor,if car is not hot than thermostat should be fine,the sensor is not hard to change-hope that helps

Does the top rubber engine to radiator hoes get hot? If yes then the new thermostat is working. Does the bottom return hose from the radiator back to the engine also get hot? If yes then the pump is OK. If not then there is a blockage in the system and this will need to be flushed out from both the radiator and the engine block using a high pressure hose. Does the radiator fan come on promptly. It should start before the bottom return hose becomes hot. If not then the temperature sensor (different from the temperature sender to the dash display) maybe at fault. Your relay maybe fine but it is the sensor that actually triggers the fan to come on. It may be just bad connection so try wiggling the wires to it when the engine has got warm. The temperature sensor is also important to let the engine computer management system (ECU)know that the engine has reached operating temperature. A failed sensor not only allows overheating but means that the ECU thinks the engine is still cold and runs the engine on a rich mix. Have you noticed lumpy idling when hot and excessive fuel consumption recently? these are symptomatic of a failing sensor.

A educated guess I would have to say there is a problem with HVAC control module ! electronics you know ! But that's not the way to do things ! There could be codes stored in the module. The Chevy dealer my have a reflash bulletin for this problem . Then can reflash , reprogram the control module ! The first place to start is checking for codes in the HVAC module.
The HVAC control module is a class 2 device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). If the battery positive voltage circuit loses power, all HVAC DTCs and settings will be erased from KAM. The body control module (BCM), which is the vehicle mode master, provides a device on signal.
Air Temperature Sensors The air temperature sensors are a 2-wire negative temperature co-efficient thermistor. The vehicle uses the following air temperature sensors:
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Ambient Air Temperature Sensor

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Inside Air Temperature Sensor Assembly

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Inside Air Temperature Sensor Assembly-Auxiliary

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Upper Left Air Temperature Sensor

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Upper Right Air Temperature Sensor

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Lower Left Air Temperature Sensor

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Lower Right Air Temperature Sensor

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Upper Air Temperature Sensor-Auxiliary

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Lower Air Temperature Sensor-Auxiliary
A signal and low reference circuit enables the sensor to operate. As the air temperature surrounding the sensor increases, the sensor resistance decreases. The sensor signal voltage decreases as the resistance decreases. The sensor operates within a temperature range between -40?° to +101?°C (-40?° to +215?°F). The sensor signal varies between 0-5 volts.
The input of the duct air temperature sensors are different from the ambient and inside air temperature sensors. The HVAC control module converts the signal to a range between 0-255 counts. As the air temperature increases the count value will decrease.
If the HVAC control module or auxiliary HVAC control module detects a malfunctioning sensor, then the control module software will use a defaulted air temperature value. The default value for the ambient and inside air temperature sensors will be displayed on the scan tool. The default value for the duct air temperature sensors will not be displayed on the scan tool. The scan tool parameter for the duct air temperature sensors are the actual state of the signal circuit. The default action ensures that the HVAC system can adjust the inside air temperature near the desired temperature until the condition is corrected.
The ambient air temperature sensor mounts underhood and can be affected by city traffic, by idling, and by restarting a hot engine. Therefore, the HVAC control module filters the value of the ambient air temperature sensor for temperature display. The ambient air temperature value is updated under the following conditions: Or you can just buy a new control module an hope that it fixes it. $89.00 at www.partsgeek.com

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sound like coolant temperature sensor is open or not working.scan it to see when engine get operating temperature when coolant temperature get 190 degrees the coolant temp sensor should show 190 degrees if it shows 80 degrees or lower it not working replace it.the coolant sensor control coolant fan.when it gets hot it resistance changes or lower.the pcm grounds it .then cooling fans will run.

is it ever low in coolant? i agree with emissionwiz sounds like your getting airpockets do you have heat when this starts?