The engine coolant temperature (ECT) sensor is a variable resistor, that measures the temperature of the engine coolant. The ECT sensor has a signal circuit and a low reference circuit. The engine control module (ECM) supplies 5 volts to the ECT signal circuit and a ground for the ECT low reference circuit. When the ECT is cold, the sensor resistance is high. When the ECT increases, the sensor resistance decreases. With high sensor resistance, the ECM detects a high voltage on the ECT signal circuit. With lower sensor resistance, the ECM detects a lower voltage on the ECT signal circuit. If the ECM detects an excessively high ECT signal voltage, which is a low temperature indication, DTC P0118 sets. You have A bad coolant temp sensor or a wiring problem !
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.
Hope that helps Matt..
SOURCE: no voltage at the engine coolant temperature
ever since 1995 you have to turn off useing a obd2 scanner, if you do not have one, you can go to any auto parts store and they will erase the code for free. by having the light still on the computer thinks it still has an error. good luck Toolman,
SOURCE: Explain these trouble codes po123,p0118 and 1193
Is it high voltage or signal high. If it is truly high voltage it could be a wire crossed with a 12 volt wire, but more likely an engine controller that has gone bad. Use a digital volt ohm meter to determine the voltage on the reference circuit. Normal voltage should be near 5 volts.
If the issue is signal high, this indicates a broken wire between the engine controller and the sensors.
Good luck.
SOURCE: p0118 engine coolant temp circuit high input what
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.
SOURCE: trouble code p0118 for a 1999 ford escort se ,
This may caused by bad connection at the sensor, short in the voltage feed between the sensor and the PCM, bad PCM, open in the ground circuit between the ECT sensor and the PCM, bad temperature sensor.
You see more here:
http://www.fixya.com/cars/t5027589-1998_honda_accord_code_po118
The coolant temp sensor is #9 in the picture. How hot does it get in degrees F? Are the radiator fan/s running?
A DTC will be set if an abnormal reading occurs, P0116 for sensor performance, P0117 low input or
P0118 for a high input. The coolant temperature sensor temperature reading should closely match the
air charge/manifold temperature reading on a scan tool if the engine has not been run for over an hour.
The sensor circuit can be checked for proper voltage using a voltmeter.
Symptoms of a P0118 could include:
A code P0118 may mean that one or more of the following has happened:
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