Engine Oil Temperature Sensor Low Voltage
The P0197 code indicates that the Engine Oil Temperature (EOT) sensor is reporting a voltage lower than the expected range, typically below 0.2 volts. This sensor is a thermistor that changes resistance with temperature; low voltage suggests either a short circuit to ground, a faulty sensor, or an open circuit in the signal wire. The PCM monitors this sensor for engine protection and performance adjustments.
01. Most Common Causes
- Faulty engine oil temperature sensor
- Short circuit to ground in the sensor signal circuit
- Open circuit in the sensor signal or ground circuit
- Corroded or damaged connector at the sensor
- Engine control module (ECM) issue (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Engine may run poorly or have reduced power
- Possible overheating or inaccurate temperature gauge
- Increased fuel consumption
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm P0197 and check for other related codes.
Step 2: Visually inspect the EOT sensor connector and wiring for damage, corrosion, or loose connections.
Step 3: Disconnect the sensor and measure resistance across its terminals; compare to manufacturer specifications (typically 100k ohms cold, 100 ohms hot).
Step 4: With the sensor disconnected, check for voltage at the harness connector (should be around 5V reference). If not, check for open or short in wiring.
Step 5: If sensor and wiring are good, suspect a faulty ECM; perform a wiggle test and verify with a known good sensor.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as the PCM may not properly protect the engine from overheating, potentially causing severe damage.
How much does it cost to fix?▼
Typically $50-$150 for parts and labor, depending on sensor location and labor rates.