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97 eclipse gs trouble code p0118 is it suggested to change temp sensor

Car doesn't overheat and gauge reads mid range (normal). Any ideas as to what to do?

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  • ZJ Limited
    ZJ Limited Feb 17, 2012

    Is so good to know good news!


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  • Cars & Trucks Master
  • 17,970 Answers

Hi Ray:
P0118 - Engine Coolant Temperature Circuit High Input
The engine coolant temperature (ECT) sensor is a thermistor screwed into a coolant passage in the cylinder head. Sensor resistance is high when coolant temperature is low and resistance drops when coolant temperature increases. The powertrain control module (PCM) provides a 5 volt reference and a ground to the sensor. The PCM monitors voltage drop to determine coolant temperature. If the ECT reads less than freezing temp. when engine has been running for more than a few minutes, the PCM determines a circuit fault and sets this code. Or if the PCM determines the sensor resistance is out of specs, this code is set.

Symptoms of a P0118 could include:
Very poor fuel economy
A no start condition
Vehicle may start, but run very poorly, blowing black smoke, running very rough and misfiring
Illumination of MIL

A code P0118 may mean that one or more of the following has happened:
A bad connection at the sensor
An open in the ground circuit between the ECT sensor and the PCM
A short in the voltage feed between the sensor and the PCM
A bad PCM (less likely)
A bad temperature sensor (shorted internally)

Possible Solutions: First, if you have access to a scan tool, check the reading of the coolant sensor. Does it read a logical number? If so, the problem is likely intermittent. Perform a "wiggle" test by wiggling the connector and harness to the sensor while watching the reading on the scan tool. Watch for any drop-outs. Drop-outs would indicate a bad connection. If the scan tool reads an illogical temperature, check the resistance of the temperature sensor. If it is out of specs, replace it. If it is in specifications, unplug the sensor and, using a fused jumper wire, jumper the two terminals of the connector together. The temperature reading should now be maxed out to above 250 degrees F. If not, there is likely a problem with the ground circuit or voltage supply.

Check for 5 volts reference voltage at the connector. Also check for ground presence at the connector. If you do not have 5V ref. and/or ground continuity, check for these back at the PCM connector. If you have these at the PCM connector, then repair open or short between the PCM and the sensor. If you do not, remove the offending wire from the PCM and then check for proper voltage at the PCM pin. If it's present now, repair short on the circuit. If it isn't present after removing the wire and checking the pin, replace PCM

NOTE: Usually, P0118 is indicative of a bad temperature sensor, but doesn't rule out these other possibilities. If you're unsure of how to diagnose a PCM, do not attempt.

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

Thank you for using FixYa, have a nice day.

Posted on Feb 16, 2012

Testimonial: "Very detailed solution. Awesome help."

  • ray M
    ray M Feb 17, 2012

    Thanks! Checked the coolant temp sensor and found a broken wire. When I pulled the connector off the sensor the pins inside the sensor came out with it. Soldered a new connection on the broken wire and replaced sensor. Cleared code and drove it for 50 miles, no codes. Problem solved. thanks for your help.

  • ray M
    ray M Feb 17, 2012

    Thanks! Checked the coolant temp sensor and found a broken wire. When I pulled the connector off the sensor the pins inside the sensor came out with it. Soldered a new connection on the broken wire and replaced sensor. Cleared code and drove it for 50 miles, no codes. Problem solved. thanks for your help.


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SOURCE: 94 Acura Legend temp gauge goes up while driving.

sound like u may have a blown headgasket or 2, have a cylinder leak down test performed , also have a block check performed... if u determine u have a blown head gasket or 2!!!, be sure to check the block for warpage and send the heads out to a machine shop to check for cracks and machined if still good.... may as well have them perform a valve job as well if u can afford it..

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SOURCE: 1993 acura legend always smoke white from exhaust

If it is excessive, your coolant may be going in the engine. Have the head gasket checked. Worst case could be a cracked head.

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SOURCE: Code P0118 on Audi A4 - Related to Ignition Coil Problem?

Hi, the sensor on the engine (right at the rear end of the cylinder head) has two separate outputs. One drives the temperature gauge and the other provides data for the engine control unit. The output for the engine control unit is almost certainly faulty and the sensor will need to be replaced. It isn't an expensive item and's not time consuming to replace (1/2 hr) - so you could ask Audi to do it for you when they replace the ignition coils.
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SOURCE: 97 2.2 cl high idle, self rev, overheat, started same time

i cannot specifically point out what the problem might be, but an overheating car---never a good thing. check everything related to cooling. fans, radiator, hoses, waterpump, coolant overflow tank(see if its got a brownish color or looks like there is oil), and check your oil while your at it...

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SOURCE: 2001 Suburban going thru coolant

the only reason you loose coolant with no apparant leaks is because you have a leaking head gasket.
Dexcool is very corrosive and eats gaskets. Most people that are aware of this replace it with the green coolant ASAP.
Do a search on dexcool problems and you will be amazed at the complaints and recomendations for class action lawsuits.
With 165,000 miles it also possible its just time. Things do break for no reason other than wear and tear.

Posted on Jul 16, 2010

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