P0128
P0128 — Coolant Thermostat Below Regulating Temperature
2
Driver reports
2
Solved cases
2
Verified fixes
0
Wrong repairs reported
📊 Diagnostic Overview
Severity, cost and difficulty for P0128, based on data already on this page.
Severity
🟢 Low
Diagnostic Difficulty
Not enough data yet
System
Engine
Common Causes (based on confirmed repairs)
- P0128 almost always means thermostat is stuck open and engine never reaches proper operating temperature. Fix: Replace thermostat — cheap part ($15-40), moderate labor. Do NOT just clear the code — running cold causes increased fuel consumption, engine we 1 vehicle
- Thermostat stuck open: engine never reaches normal operating temperature (usually 180-200°F). Problems caused: 1) Poor fuel economy — ECU adds extra fuel for cold engine. 2) Heater barely works. 3) Engine wear — oil does not thin properly, clearances not 1 vehicle
📐 Diagnostic Difficulty reflects how many different repairs drivers have tried for P0128 and how often those attempts turned out to be the wrong fix — it is calculated from MyCarFault's own reports, not an official manufacturer rating.
⭐ MOST VERIFIED FIX FOR P0128
P0128 almost always means thermostat is stuck open and engine never reaches proper operating temperature. Fix: Replace thermostat — cheap part ($15-40), moderate labor. Do NOT just clear the code — running cold causes increased fuel consumption, engine we
Worked in 0% of voted outcomes
·
Verified by 0 drivers
⚪ Unverified
Most Verified Fixes for P0128
Ranked by confidence score — same vehicle matches weighted higher.
Driver Reports — P0128 2 reports
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