DTC P0198: Engine Oil Temperature Sensor ‘A’ Circuit High

In the intricate landscape of automotive diagnostics, diagnostic trouble codes (DTCs) serve as illuminating signals, pointing to potential issues within a vehicle’s complex systems. Among these, DTC P0198 takes center stage as a significant indicator of problems related to the Engine Oil Temperature Sensor ‘A’ circuit high. This comprehensive article delves into the causes, symptoms, inspection procedures, and effective solutions for addressing and resolving DTC P0198.

1. Causes of DTC P0198:

DTC P0198 arises when the Engine Control Module (ECM) detects a high input signal in the Engine Oil Temperature Sensor ‘A’ circuit. The underlying causes can include:

– Faulty Engine Oil Temperature Sensor ‘A’: A malfunctioning or out-of-spec sensor can produce abnormally high temperature readings.

– Wiring and connector problems: Damaged or corroded wiring and connectors within the sensor circuit can lead to signal issues.

– Short to voltage: A short circuit introducing voltage into the sensor circuit can result in high input signal.

– Overheating issues: Overheating in the engine or oil system can lead to high readings.

2. Symptoms of DTC P0198:

Recognizing the symptoms associated with DTC P0198 aids mechanics in making an accurate diagnosis:

– Inaccurate engine oil temperature readings: Faulty sensor ‘A’ can lead to incorrect temperature calculations.

– Engine management issues: High temperature sensor ‘A’ readings can lead to improper engine management and performance.

– Illuminated Check Engine Light (CEL): DTC P0198 triggers the CEL to alert the driver of a potential problem.

3. Inspection of DTC P0198:

Meticulous inspection techniques are crucial for accurate diagnosis:

– OBD-II scan: Utilize an OBD-II scanner to retrieve the DTC and accompanying freeze frame data, providing insight into the conditions that activated the code.

– Visual examination: Inspect the Engine Oil Temperature Sensor ‘A’ wiring and connectors for visible signs of damage or corrosion.

– Engine and oil system check: Inspect for any signs of engine overheating or issues within the oil system.

4. Resolving Causes of DTC P0198:

Addressing DTC P0198 requires specific steps tailored to the underlying issue:

– Engine Oil Temperature Sensor ‘A’ replacement: Replace a malfunctioning sensor with a new, high-quality unit that meets manufacturer specifications.

– Wiring and connector repair: Repair or replace damaged wiring and connectors to ensure accurate signal transmission.

– Overheating issue resolution: Address any engine or oil system overheating problems to prevent future inaccuracies.

5. Clearing DTC P0198:

After effectively resolving the underlying cause, clear the DTC from the ECM’s memory using an OBD-II scanner. This step confirms the issue’s resolution and prevents the CEL from reappearing.


DTC P0198, indicative of a high input signal in the Engine Oil Temperature Sensor ‘A’ circuit, underscores the importance of accurate sensor readings for optimal engine performance. By comprehending its causes, recognizing its symptoms, employing meticulous inspection techniques, and implementing effective solutions, mechanics can accurately diagnose and rectify this issue. Ensuring reliable sensor performance is pivotal for achieving optimal engine functionality, fuel efficiency, and overall vehicle operation.