P0197 - Engine Oil Temperature Sensor Low
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System
Powertrain (Engine & Gearbox)
Related Fault Codes
Technical Description
P0197 is set when the Engine Control Unit (ECU) detects that the voltage signal from the Engine Oil Temperature (EOT) sensor is below the minimum calibrated limit (typically below 0.2V to 0.5V). The EOT is usually an NTC thermistor where resistance decreases as temperature increases. A very low voltage signal is interpreted by the ECU as a short to ground or an out-of-range high temperature reading, potentially triggering limp mode or cooling fan activation to protect the engine.
Possible Causes
Faulty Engine Oil Temperature (EOT) sensor (internal short)
Short to ground in the signal wire harness
Corroded or damaged connector at the sensor
Internal Engine Control Unit (ECU) failure
Symptoms
Recommended Solution
Workflow
Mechanic's Tip
Before replacing expensive components, always double-check wiring and connections. 80% of all sensor faults are actually due to corroded contacts or broken wires.
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