How to Check & Replace an Engine Coolant Sensor

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Can Unhealthy Coolant Temperature Sensor Trigger Automotive To Stall?

Signs of a nasty sensor differ, however a verify engine gentle would be the frequent denominator. It’s such an necessary sensor. The engine gentle will alert the motive force as quickly because the onboard pc senses an issue.

As you understand, the sensor is central to how the engine management modules make choices about fueling, a flawed studying will trigger poor operating, and stalling is excessive on an inventory of signs.

Different frequent signs embody:

  • Onerous on fuel
  • Robust scent of fuel
  • Tough operating
  • Hesitation on acceleration
  • Excessive or low idle
  • Misfiring
  • Black smoke
  • Unhealthy scent from the muffler
  • Overheating engine
  • Fan operating fixed
  • HVAC blows cool air

What Does the Coolant Temperature Sensor Do?

Mainly, your engine coolant temperature sensor (CTS or ECTS) displays the temperature of the coolant circulating by your automobile’s engine. In flip, this offers an thought of how scorching your engine is. In case your engine is overheating, it’s as much as the coolant temperature sensor to select up on that data and set off the dashboard gentle, in addition to every other responses your automobile is ready to hold out.

Many fashionable vehicles will robotically shut off the engine as soon as it reaches a sure temperature to guard it from extreme injury. In case your coolant temperature sensor isn’t doing its job correctly, the engine might not obtain the sign to close off  and also you would possibly end up going through severe engine injury.

First 3 Issues to Examine if Your AC Stops Working

Having hassle staying cool this summer season? When your automobile’s AC stops working, it may possibly make any drive really feel like a chore. Discovering the issue behind your automobile’s AC hassle can really feel difficult, however there are a number of key areas the place you can begin trying. We’ll check out three…

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Can You Drive With a Defective Coolant Temp Sensor?

Whereas a car with a defective coolant temperature sensor can usually be pushed from one location to the subsequent, doing so isn’t suggested. With time, lots of the particular person signs of a failing coolant temperature sensor can develop into problematic themselves. 

An inoperable fan attributable to a defective coolant temperature sensor will rapidly lead to engine overheating. In consequence, further issues, similar to head gasket leaks, can come up.

Likewise, abnormally excessive gas charges attributable to skewed knowledge from a defective sensor, can result in the superheating and failure of a car’s catalytic converter.

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On 1996 and newer autos with OBD II onboard diagnostic methods, a defective coolant sensor might forestall a number of the system displays from operating. This can forestall the car from passing an OBD II emissions take a look at as a result of the take a look at can't be achieved except all of the required system displays have run and handed.

The OBD II system ought to catch the fault, activate the Examine Engine Mild or Malfunction Indicator Lamp (MIL), and set one of many following diagnostic trouble codes: P0115….Engine Coolant Temperature Circuit P0116….Engine Coolant Temperature Circuit Vary/Efficiency P0117….Engine Coolant Temperature Circuit Low Enter P0118….Engine Coolant Temperature Circuit Excessive Enter P0119….Engine Coolant Temperature Circuit Intermittent

On older pre-OBD II autos, the Examine Engine gentle might come on if the coolant sensor is shorted, open or is studying out of vary. GM coolant sensor codes embody codes 14 & 15, Ford codes are 21, 51 & 81, and Chrysler codes are 17 & 22.

Coolant Temperature Sensor Alternative Price

The typical coolant temperature sensor substitute value is between $50 and $250, relying on the automobile mannequin and labor prices. A coolant temperature sensor prices $30 to $100, and the labor prices $20 to $150.

The coolant temperature sensor itself is usually fairly low cost and you’ll usually discover them round $40 for a high quality one. There are cheaper ones available on the market, however I closely suggest shopping for a high quality one like Bosch to skip the complications.

The substitute is usually additionally fairly simple, besides that you simply may need to pour out all coolant from the engine and refill it – which signifies that you need to take away all air from the coolant system, which may be troublesome.

Nevertheless, in case you are quick changing the sensor, there’s usually no have to faucet out the coolant, however this requires some expertise.

Bear in mind to at all times be certain the coolant temperature is low when doing this sort of work!!

Find out how to Spot a Defective Coolant Temperature Sensor

Like every part below the bonnet, coolant temperature sensors can develop faults over time. A defective sensor can result in a spread of issues creating, together with overheating and poor engine efficiency. That’s why it’s necessary to know learn how to spot the indicators of a defective or failing temperature sensor, earlier than it may possibly trigger additional issues which might show costlier to repair.

Begin by taking a look on the unit itself to verify its situation, as sensors/gaskets/connectors can develop cracks with prolonged use and continuous temperature biking. The CTS is normally discovered on the entrance of the automobile, close to the thermostat housing, or on the radiator. Whereas a visible verify may help to diagnose some faults, not all issues with a CTS present seen signs.

Under, we listing the opposite indicators and signs which might point out a CTS concern:

  • Irregular studying of the dashboard gauge (needs to be 88-90°C when the engine is warmed up)
  • Overheating engine (highlighted by dashboard gauge)
  • Examine Engine Mild alert on dashboard
  • Tough engine sound whereas idling
  • Restricted efficiency (attributable to ECU miscalculating gas wealthy combination)
  • Poor gas financial system

If in any doubt about which part is defective beneath the bonnet, take your automobile to knowledgeable mechanic for a whole prognosis.

Diagnosing a Malfunctioning Coolant Temperature Sensor

Diagnosing needs to be the job of an authorized technician. Nevertheless, this shouldn’t cease you from inspecting the engine part if you happen to suspect it’s malfunctioning.

You will have to get your arms on a restore guide for the mannequin of your car. This can allow you to seek out the measurement values {that a} functioning coolant temperature swap ought to exhibit.

Examine the service guide of your car to find your coolant temperature sensor. Whenever you set eyes on it, disconnect the connector plugs.

In case your sensor has two pins, decide the ohm measure between the pins. Then examine the worth with the right ohm-value – at a given temperature – in your restore guide. If the worth doesn’t tally, it means that you must change the coolant temperature sensor.

If the values add up or tally, contemplate checking the connectors and wirings between the sensor and the engine’s management module.

It’s also possible to make use of an OBD2 Scanner to search for associated hassle codes. Examine the dwell knowledge to see the temperature of the sensor. If the temperature is off the vary, verify the wirings of the sensor or change the engine part.

What Occurs If You Unplug The Coolant Temp Sensor?

Unplugging the engine coolant sensor whereas the automobile is operating will seemingly trigger the engine to stumble and run tough. The engine gentle might not come on imminently, however a DTC (Diagnostic Bother Code) will probably be logged within the PCM.

You might also discover the engine fan activate and off intermittently. The engine will run wealthy, so that you’ll scent uncooked fuel, and you may even see black smoke from the tailpipe.

Unplugging the engine coolant temperature sensor earlier than beginning the engine might lead to a no-start, particularly seemingly on a chilly morning. Though the PCM will see the sensor is unplugged and has a default fueling technique for such an occasion. It’s extra of a one-size-fits-all method, and so a chilly begin in colder temperatures might forestall the engine from beginning.


It’s also possible to use a voltmeter or digital storage oscilloscope (DSO) to verify the sensor's output. Specs differ, however usually a chilly coolant sensor will learn someplace round 3 volts. Because the engine warms up and reaches working temperature, the voltage drop ought to step by step lower right down to about 1.2 to 0.5 volts. Should you're utilizing a scope to show the voltage sign, you need to get a hint that step by step slopes from 3 volts right down to 1.2 to 0.5 volts in three to 5 minutes (or nevertheless lengthy it usually takes the engine to succeed in regular working temperature).

If the voltage drop throughout the coolant sensor reads at or close to 5 volts, it means the sensor is open or it has misplaced its floor connection. If the voltage is near zero, the sensor is shorted or it has misplaced its reference voltage.

When engaged on older Eighties classic Chrysler merchandise, be careful for a sudden voltage enhance because the engine warms up. That is regular and is produced by a 1000 ohm resistor that switches into the coolant sensor circuit when the sensor's voltage drops to about 1.25 volts. This causes the voltage to leap again as much as about 3.7 volts, the place it once more continues to drop till it reaches a completely warmed up worth of about 2.0 volts.

Typically a coolant sensor will all of a sudden go open or quick when it reaches a sure temperature. In case your voltmeter has a "minimal/most" perform, you may catch sudden voltage fluctuations whereas the sensor is warming up. If you’re viewing the voltage sample on a scope, a brief will seem as a sudden drop or dip within the hint to zero volts. An open would make the hint leap as much as the VRef voltage line (5 volts).

If the coolant sensor reads usually when chilly (excessive resistance and three or extra volts), however by no means appears to succeed in regular temperature it might be telling the reality! An open thermostat or the flawed thermostat could also be stopping the coolant from reaching its regular working temperature.

Changing the Automotive Temperature Sensor

The sensor will ultimately should be changed altogether after time. If the engine sustains any sort of trauma or injury, sensor substitute is at all times really helpful since you don’t need to threat operating the car with a defective one. Even common put on and tear could cause the sensor to erode over time.

You possibly can at all times have your CTS changed by an auto care skilled. This side of preventative upkeep can definitely save you some complications and trouble in the long term.

Trace – if you happen to can’t discover a temperature sensor in your automobile – this article should help.