P0198 Engine oil temperature sensor signal high

P0198 – OBD-II Trouble Code Technical Description

Engine oil temperature sensor, high signal level

What does trouble code P0198 mean?

This trouble code (DTC) is related to transmissions and applies to OBD-II equipped vehicles such as Ford Powerstroke, Chevrolet GMC Duramax, VW, Nissan, Dodge, Jeep, Audi and others. The exact repair steps may vary depending on the make and model.

The engine oil temperature (EOT) sensor sends a signal to the control module (PCM) for fuel system, injection timing and glow plug calculations. EOT is also compared to other temperature sensors such as the Intake Air Temperature (IAT) sensor and the Engine Coolant Temperature (ECT) sensor. These sensors are often used in diesel engines. EOT sensors receive voltage from the PCM and change resistance based on oil temperature. Code P0198 occurs when the PCM detects a high EOT signal, which usually indicates an open circuit.

Other related codes include P0195 (sensor failure), P0196 (range/performance problems), P0197 (signal low), and P0199 (sensor intermittent).

What are the symptoms of the P0198 code?

The only sign is that the Check Engine light is on. The EOT system is designed to detect other problems with the vehicle, and if its circuitry becomes faulty, it may be unable to control oil temperature. This manifests itself through the check engine light (or engine maintenance light).

How serious is trouble code P0198?

The severity of these codes can range from moderate to severe. In some situations, especially if they are accompanied by codes related to coolant temperature, this may indicate an overheating engine. Therefore, it is recommended to resolve these codes as soon as possible.

Possible reasons

1. EOT circuit short circuit to power
2. The powertrain control module (PCM) is faulty
3. Low engine oil temperature
4. Engine cooling system problems
5. Wiring problems
6. Defective engine oil temperature sensor
7. The engine oil temperature sensor harness is open or shorted.
8. Engine Oil Temperature Sensor Circuit Poor Wiring

How is code P0198 diagnosed?

To diagnose this code, first perform a visual inspection of the engine oil temperature sensor and its wiring to look for damage, loose connections, or other problems. If damage is found, it should be repaired, then reset the code and see if it returns.

After that, check for technical service bulletins (TSBs) related to this issue. If no TSBs are found, proceed to step-by-step system diagnostics following the manufacturer's instructions. Check the operation of the cooling system, ensuring that the engine maintains the correct operating temperature.

Next, test the engine oil temperature sensor circuit using a multimeter. Connect and disconnect the EOT sensor and check how the multimeter reading changes. If the readings change suddenly, the sensor is most likely faulty. If not, the sensor should be replaced.

Check voltage reference circuit: Make sure the EOT is receiving reference voltage from the PCM. If not, check the reference voltage circuit for an open. Next, test the ground signal circuit, making sure the ground connections to the EOT and PCM are working properly.

This code likely indicates a short in the EOT circuit, and you will need to do a thorough wiring diagnostic to find and repair this short.

Diagnostic errors

• A technician may replace the sensor without checking the wiring to and from the EOT sensor.
• Unable to control the reference voltage, the PCM/ECM supplies it to the sensor.
• It is not possible to detect other problems that may be contributing to the low oil temperature.

How serious is trouble code P0198?

This code is unlikely to cause serious damage to the vehicle, but there is a small chance that it could cause some problems. Anytime the PCM applies maximum voltage (12,6-14,5V) to circuits designed for lower voltages, it can cause damage. However, most modern vehicles have systems designed to protect against such damage if the voltage exceeds what is expected.

What repairs will fix the P0198 code?

1. Repair damaged wiring, eliminate short circuit in the power supply.
2. Repair the PCM (powertrain control module).
3. Solve the problem of low engine oil temperature.

What is P0198 Engine Code [Quick Guide]

P0198 KIA

The engine oil temperature sensor is used to measure the temperature of the engine oil. This sensor changes the voltage and sends the modified signal to the engine control module (ECM), which is then used as an input signal to measure the engine oil temperature. The sensor uses a thermistor, which is sensitive to temperature changes. The electrical resistance of a thermistor decreases as the temperature increases.

The P0198 code is a universal code that is used by all manufacturers and has the same definition.

Each manufacturer uses its own diagnostic method to test this system. This code is often used in high-performance vehicles designed for extreme driving conditions. Such conditions are outside the scope of normal driving, which explains why EOT is not used in most everyday vehicles.