P1199 – Engine Coolant Temperature Sensor Range/Performance
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Symptoms
- Slow warmup
- Poor fuel economy
- Heater not warm
- Check engine light
- Rough idle
Causes
- Faulty temp sensor
- Low coolant
- Wiring issue
- Connector problem
- ECU issue
Diagnosis
- Inspect wiring
- Test sensor resistance
- Check coolant level
- Inspect connectors
- Scan live data
Repair
- Replace temp sensor
- Refill coolant
- Repair wiring
- Fix connectors
- Bleed cooling system