Engine Oil Temperature Sensor Intermittent
The P0199 code indicates that the Engine Control Module (ECM) has detected an intermittent signal from the Engine Oil Temperature (EOT) sensor. This sensor monitors oil temperature to optimize engine performance and protect against overheating. An intermittent fault may be caused by a loose connection, damaged wiring, or a failing sensor. If left unaddressed, it can lead to inaccurate temperature readings, potentially causing engine damage due to overheating or improper fuel mixture.
1. Most Common Causes
- Faulty engine oil temperature (EOT) sensor due to internal thermistor degradation
- Corroded, loose, or moisture-contaminated electrical connections at the EOT sensor connector
- Damaged EOT circuit wiring from chafing, heat exposure, or rodent activity causing intermittent shorts
- Intermittent engine control module (ECM/PCM) failure in processing the analog signal
- Excessive ground circuit resistance in the sensor due to corroded grounding points
- Electromagnetic interference from nearby electrical components affecting the wiring
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Engine performance issues (rough idle, hesitation)
- Inaccurate oil temperature gauge reading
- Possible overheating or poor fuel economy
3. Step-by-Step Diagnosis
Step 1: Scan for codes and record freeze frame data.
Step 2: Visually inspect the EOT sensor and wiring for damage, corrosion, or loose connections.
Step 3: Test the sensor resistance and compare with manufacturer specifications.
Step 4: Check for intermittent faults by wiggling the wiring harness while monitoring the sensor signal with a scan tool.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive for extended periods as the ECM may not accurately detect overheating, which can cause engine damage.
How much does it cost to fix?▼
Typically between $50 and $150 for parts and labor, depending on the vehicle and shop rates.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.