P0198 code definition
Engine Oil Temperature (EOT) Sensor High
What the P0198 code means
This code indicates there is higher voltage than expected in one or all of the circuits involving the EOT system (low oil engine temperature).
What causes the P0198 code?
- Short to power in the EOT circuit
- Faulty powertrain control module (PCM)
- Low engine oil temperature
What are the symptoms of the P0198 code?
The only symptom is the Check Engine Light. The EOT system is there to detect other problems with the vehicle. If the circuits of the EOT system have problems, it will be unable to monitor the oil temperature.
How does a mechanic diagnose the P0198 code?
This code most likely indicates a short to power in the EOT electrical system. A scan tool should be used to observe sensor data to confirm this condition. Direct testing of the EOT circuits with a multimeter should performed to pinpoint the source of the short to power.
Each section of wiring should be isolated and tested to determine where the short to power is. This is followed by carefully inspecting the wiring harness for damage. Often, it is necessary to wiggle the suspected harness while observing the scan tool or multimeter watching for a change in voltage.
Common mistakes when diagnosing the P0198 code
- A technician can choose to replace the sensor without checking the wiring going to and from the EOT sensor.
- Failing to check the reference voltage the PCM/ECM provides to the sensor.
- Failing to detect other problems that may contribute to low oil temperature.
How serious is the P0198 code?
This code is not likely to cause a vehicle to break down. However, there is some potential for this to occur. Anytime a PCM has full voltage (12.6 - 14.5 volts) applied to circuits that were designed for lower voltage, damage can occur. Fortunately, most modern vehicles have designed these systems to resist such damage in the event that a higher than expected voltage should occur.
What repairs can fix the P0198 code?
- Repairing damaged wiring supplying the short to power
- PCM repair
- Addressing the low engine oil temperature
Additional comments for consideration regarding the P0198 code
A P0198 code is a generic code that all manufacturers can use and must always retain the same definition.
Each manufacturer utilizes a different diagnostic method for the testing of this system. Even then, it is often used in performance vehicles that are designed to be driven very hard. Driving in racing conditions pushes the vehicle to the limits of its engineering beyond what an everyday driver will experience. For this reason, an EOT system is not common on most vehicles.
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