The thermostat does not close so the engine never reaches its normal operating temperature.
This generic fault record is not vehicle-specific. Applicability and repair choice must be resolved from vehicle context and test results.
Thermostat stuck open
At a glance
Fault summary
The thermostat does not close so the engine never reaches its normal operating temperature.
SeveritySeverity not yet verified Drive?Depends on the exact symptoms EvidenceSource notes available
- Affected system
- Cooling
- Severity
- Severity not yet verified
- Urgency
- Urgency not yet verified
- Can I drive?
- Depends on the exact symptoms Drivability is governed by symptoms and the approved diagnostic safety layer, not by this generic failure-mode label alone.
- Repair/cost band
- Cost band not yet verified
- Vehicle applicability
- No structured vehicle applicability verified yet
- Evidence/confidence
- Source notes available See source & evidence notes below
Short answer
The thermostat does not close so the engine never reaches its normal operating temperature.
Drive?Depends on the exact symptoms
Can I still drive with this?
Depends on the exact symptoms
Drivability is governed by symptoms and the approved diagnostic safety layer, not by this generic failure-mode label alone.
Common symptoms
- The temperature gauge never comes up
- The heater blows cold
- It is using more fuel than it used to
Likely causes
- Normal service wear
Diagnosis checks
Check the thermostat with a thermometer
Check the heater
Used-car buyer warning
Ask for documented diagnosis and repair evidence; do not infer this fault from one symptom or code.
Repair actions / cost band
Repair action and cost band are not yet verified.
Source & evidence notes
- CarFaultIQ diagnostic failure mode fm_thermostat_stuck_open, manifestation relationships and test effects. Safety review status: pending_human_review. No vehicle-specific prevalence is claimed.