Error p0118 stands for “coolant temperature sensor - high signal level.” It occurs if the electronic engine control unit (hereinafter referred to as the ECU) detects that a voltage above the threshold is supplied from the specified sensor, that is, above 4.91 Volts. Most often, the cause of error p0118 is an open circuit of the sensor or failure of the sensor itself. Eliminating the error code and the problem itself in general consists of one of the following options - replacing the wires of the sensor circuit, replacing the sensor connector, replacing the sensor itself with a new one.
What are the symptoms of a P0118 code?
- When this error appears, the Check Engine light will light up on the vehicle's dashboard. The ECM will put the engine into limp mode, replacing the incorrect coolant temperature sensor reading with a value of 80°C (176°F).
- The car engine may be difficult to start when cold. When warm, the engine starts normally.
- The car engine may run rough until it warms up.
- After warming up, the engine usually runs normally.
Note : Symptoms of this error may vary depending on the make and model of your vehicle.
Where is the sensor located
The location of the described unit is the engine compartment near the cylinder head (on the exhaust pipe), the thermostat. This is a standard location, for example, like the VAZ 2114. Appearance - plastic, rectangular box, plug with a metal part with a thread and a contact segment. There are 2, less often 3, wires going to the device.
How does a mechanic diagnose a P0118 code?
When diagnosing this error, the mechanic will do the following:
- Visually inspect the coolant temperature sensor and related electrical wires and connector
- Reads all stored data and error codes using an OBD-II scanner to find out when and under what circumstances the P0118 error occurred
- Clear the error codes from the computer's memory and test drive the vehicle to see if the P0118 code appears again
- Check the electrical wires and coolant temperature sensor connector for corrosion and damage.
- Observes the coolant temperature sensor readings in real time using a scanner
- If necessary, replace the coolant temperature sensor, associated electrical wires and connector, or engine control module (ECM)
When P0118 is output, clearing the controller memory from it
Sensor signal error P0118 (its code) appears in the ECU controller memory under the following conditions (generalized, there may be differences for some brands):
- The internal combustion engine runs from 120 seconds;
- 0.2 sec. voltage from the detector as at t° below -42 or -38 (may vary slightly for different vehicles);
- if the malfunction is persistent after 2 drive cycles, then CHECK ENGINE is displayed.
We summarize the conditions under which the code is deleted from the ECU controller (the memory is cleared):
- CHECK ENGINE disappears (turns off) if the control system does not detect a malfunction after 4 cycles of starting the engine;
- The diagnostic history becomes clear after 40 consecutive heating cycles of antifreeze in the absence of a problem.
How serious is P0118?
When P0118 occurs, the vehicle's ECM will put the engine into limp mode. Staying in limp mode may result in unstable engine operation, which will continue until the engine warms up to normal operating temperature. Possible increased fuel consumption and excessive carbon buildup on engine components. Driving a vehicle in limp mode for long periods of time can lead to a number of other problems, including problems with the ignition system. Also, the cooling system fans can run continuously.
What does code P0118 mean?
Modern cars have an electronic monitoring system (ECM) of the state of the internal combustion engine with a control unit (ECU). By connecting a diagnostic scanner-adapter to the unit, you can find out about the operation of the motor. Data is displayed in brief alphanumeric notifications. These codes include P0118, which indicates that excessive voltage has been detected on the coolant temperature sensor (CTS) circuit. Appears when 4.91 V is exceeded.
So, if the output voltage of the coolant sensor (detector, detector) that monitors the temperature level of antifreeze exceeds 4.91 V, then the ECM registers a problem in its circuit and signals this with code P0118, which can be seen on the display of the diagnostic adapter connected to the ECU.
Explanation of the described error: “high signal level”. The coolant sensor is a thermistor; a 5 V power supply is supplied to it from the ECU. The detector returns a voltage that decreases as t° increases. In this way, monitoring and feedback from the system occurs. Code P0118 shows that the internal combustion engine control unit detects an excessively high incoming voltage from the device, the normal level of which is 1.5 - 2 V. For most vehicles, the threshold is 4.91 V. The ECU forcibly deactivates the sensor, following its programmed algorithm, and makes a switch to emergency condition. Plus, the impellers of the cooling system can be activated; they are constantly running on the radiator.
Symptoms of malfunction
The main driver symptom of P0118 is the MIL (Malfunction Indicator Light). It is also called Check engine or simply “check light”.
They can also appear as:
- The “Check engine” warning light on the control panel will light up (the code will be stored in the ECM memory as a malfunction).
- The engine stalls or has difficulty starting (especially when starting from cold).
- Floating speed, as well as attempts to stall at idle.
- Car engine overheating.
- Black smoke from the exhaust pipe when running on a rich mixture.
- On a lean mixture, increased NOx emissions may occur.
- Incorrect operation of cooling fans.
Error P0118 is not serious, the car will be able to start and continue driving. But it is better to solve it as soon as possible, since improper heat transfer can lead to more serious consequences.
How to carry out repairs
If OBD P0118 is detected in the ECU memory, do the following:
- The ignition is activated, but the engine does not start.
- A diagnostic vehicle error scanner is connected to the ECU (to its connector), and it also receives data on the parameters of the entire system. Select “t° cooling” in the menu. liquid."
- If the temperature of the antifreeze on the instruments is below +135°, then if there are no other errors in the control unit’s memory, check the grounding of the sensor (integrity of wiring, contacts). The electrical circuit diagram is in the technical documentation of the vehicle and the device. At the same time, check all connections.
- Snap off the block (chip) with the conductors. If the device continues to show above +42°, then its signal wire is shorted to ground or the ECU is broken. If it is lower, then there is a problem in the sensor itself, in which case there is only one way out - replacement (but after preliminary additional testing).
The coolant sensor is in direct contact with the cooler, so if there are signs of overheating, it should not be removed.
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