Understanding and Resolving a P0128 Code on a 2008 Ford Focus SE

QuestionsCategory: Ask An ExpertUnderstanding and Resolving a P0128 Code on a 2008 Ford Focus SE
Lillian Karen Hill asked 7 months ago
I recently purchased a 2008 Ford Focus SE with approximately 87,000 miles on it. The car passed emissions testing, but I've noticed some issues. The temperature gauge consistently reads on the cooler side, and there's a noticeable vibration at idle due to a lower RPM. Additionally, the engine coolant level is near the "hot full" line when the car is off, which seems unusually high. Just yesterday, the engine light turned on after about 10 minutes of driving. I used an OBD code reader and it displayed a P0128 code. There haven't been any changes in the car's sounds or handling. My boyfriend, who is knowledgeable about cars, suggested the overfilled coolant might be excessively cooling the engine. What could be causing these issues, and how should I address them?
1 Answers
Zack Norman Staff answered 7 months ago
Hi there, Lillian! Thanks for reaching out with your concern. The P0128 code in your 2008 Ford Focus SE is indicative of an issue with the engine's coolant temperature. It typically means that the measured coolant temperature is too low for optimal engine performance. This doesn't necessarily relate to having too much coolant; rather, it often points to a thermostat that is stuck open. The thermostat should open at around 195°F to regulate the engine's temperature, but if it's stuck, it can't perform this function effectively. Driving with this issue for a short period shouldn't cause immediate harm, but it's not advisable in the long term. The key solution here is to replace the thermostat. Ensure to avoid "Fail Safe" thermostats as they can falsely fail open; instead, opt for a STANT or original equipment (OE) thermostat. Also, the overfilled coolant level shouldn't cause the engine to run cold, but it's good practice to keep it within the recommended levels to avoid other potential issues. In terms of the low RPM and vibrations at idle, this might not be directly related to the P0128 code. It could be due to other factors like engine tuning or idle control valve issues. It's best to have a professional mechanic inspect this separately. If you have any more questions or need further assistance, feel free to reach out! Zack - Motor Verso Mechanics Team