P0197: Engine Oil Temperature Sensor Circuit Low

Check Engine Light illuminated; possible incorrect oil temperature reporting which can affect fuel/engine management and potentially reduce performance or efficiency.

Overview

P0197 is a generic OBD-II powertrain code indicating the engine oil temperature sensor circuit is reporting a low voltage signal to the PCM, often due to sensor or wiring issues.

Common Symptoms

Check Engine Light illuminated
Oil temperature gauge reads unusually low or erratic
Poor fuel economy or rough idle
Difficulty starting in cold conditions

Most Common Causes

Faulty engine oil temperature (EOT) sensor high

Sensor fails to provide correct voltage signal to PCM.

Damaged or corroded wiring/connectors in EOT circuit high

Shorts or open circuits can pull voltage low causing false readings.

Poor reference voltage from PCM or PCM input circuit failure medium

Less common; PCM internal fault affecting sensor signal interpretation.

Engine cooling system abnormality low

Secondary issue that may affect oil temperature readings in rare cases.

Diagnostic Steps

Read stored codes and live data with an OBD-II scan tool.

Expected: P0197 present and oil temp sensor data low or erratic.

Interpretation: Confirms the sensor circuit is triggering the code; proceed to inspect wiring/sensor.
Visually inspect EOT sensor and wiring harness for damage/corrosion.

Expected: No physical damage or loose connectors.

Interpretation: Damage present indicates wiring repair needed; if none, continue electrical testing.
Measure sensor circuit voltage and resistance using a multimeter.

Expected: Reference voltage (around 5V) at connector and sensor resistance varying with temperature.

Interpretation: Low or constant values indicate sensor or circuit fault.
Check PCM reference voltage and ground continuity.

Expected: Stable reference voltage and good ground.

Interpretation: If absent or out of spec, potential PCM fault.

Repair Solutions

Replace engine oil temperature sensor medium

Estimated Cost: $80 - $250

Sensor replacement is most common and often resolves the low circuit signal.

Repair or replace wiring/connectors medium

Estimated Cost: $50 - $200

Correct damaged harness or corroded connector to restore proper signal.

Reprogram or replace PCM hard

Estimated Cost: $300 - $1200

Only if confirmed PCM input circuit fault remains after tests.

Common Misdiagnoses

Avoid these common diagnostic mistakes:

Fuel rail pressure sensor circuit fault (incorrect interpretation)
Coolant temperature sensor fault
General engine overheating without verifying oil temperature sensor circuit

Frequently Asked Questions

Technical definition of P0197 OBD-II Code

Technically, the P0197 code represents Engine Oil Temperature Sensor Circuit Low. It usually points to a fault within the Sensors.

How serious is the P0197 code?

This is a medium priority issue. Check Engine Light illuminated; possible incorrect oil temperature reporting which can affect fuel/engine management and potentially reduce performance or efficiency.

How do I know if I have code P0197?

Drivers often report: Check Engine Light illuminated, Oil temperature gauge reads unusually low or erratic, Poor fuel economy or rough idle when this code is present.

Why is my car throwing a P0197 code?

Potential culprits include: Faulty engine oil temperature (EOT) sensor, Damaged or corroded wiring/connectors in EOT circuit, Poor reference voltage from PCM or PCM input circuit failure. A proper diagnosis is recommended.

Is P0197 expensive to fix?

The cost varies significantly based on the root cause. For example, replacing a Repair or replace wiring/connectors typically costs between $50 and $200, while fixing a Reprogram or replace PCM can range from $300 to $1200.

Does code P0197 apply to Honda vehicles?

P0197 is not specific to any one brand. It can appear on Ford, Dodge, Toyota, Honda, Jeep, and other vehicles.

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