Check Engine Code
P0125
Insufficient Coolant Temperature for Closed Loop Fuel Control
What P0125 means
The ECM uses ECT to decide when to switch from open-loop (fixed fuel map) to closed-loop (O2 sensor feedback). If the engine never warms up, it stays in open-loop and burns more fuel.
Symptoms
- Check engine light
- Poor fuel economy
- Cold heater output
- Low temp gauge reading
Likely causes (most common first)
- Thermostat stuck open (most common — same fix as P0128)
- Failed ECT sensor reading low
- Low coolant
Can I keep driving?
Low — mostly emissions/economy
Typical repair cost
DIY fixes can start near $20 (parts only). Shop repairs for P0125 typically run up to $300 depending on the underlying cause and vehicle. Start with the most common cause — Thermostat stuck open (most common — same fix as P0128) — before throwing parts at it.
Symptoms that match P0125
If you got here from a search query, one of these might describe what your car is actually doing:
Recommended parts & tools for P0125
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