Engine code
P0117: Coolant temperature signal too low
How this range is built
| Part of the job | Low | High |
|---|---|---|
| Parts | $15 | $60 |
| Labor: 0.6 to 1 hours × $125 to $175 an hour | $75 | $175 |
| Fees: shop supplies, disposal, diagnostics | $10 | $25 |
| Total, rounded | $100 | $260 |
The hourly rate is the BLS Occupational Employment and Wage Statistics, May 2025 average pay for this trade in Boston, $31.54 an hour, times 4 to 5.5 to cover what a shop bills (overhead, tools, insurance, profit). Parts are a band from budget aftermarket to the manufacturer part. Full method.
Not a repair shop, estimates only. Typical range, estimate. Not a quote. Your car, parts and shop change the number.
This is the range for the most common fix, coolant temperature sensor replacement. Which repair your car needs depends on a proper diagnosis.
The coolant temperature sensor is sending a reading so cold that it looks like an open circuit. The computer may think the engine is always cold, so it adds extra fuel and keeps the cooling fan running. That wastes fuel and can make restarts rough when the engine is warm.
- Safe to drive?
- Usually yes, for now
- Most common cause
- Failed coolant temperature sensor
You can drive a short distance, but if the real engine temperature rises the gauge may not show it, so watch for overheating.
What you may notice
- Hard starting when warm
- Poor mileage
- Cooling fan running all the time
- Black smoke
Common causes, most likely first
- Failed coolant temperature sensor
- Corroded connector
- Broken wiring
- Low coolant
- Computer fault (rare)
Check this first
Check the coolant level when the engine is fully cool, then look at the sensor plug for corrosion or a loose latch. A low coolant level can leave the sensor sitting in air, which is worth ruling out first.
Other repairs that sometimes fix P0117
| Repair | Typical range, Boston |
|---|---|
| Thermostat replacement | $120 to $470 |
| Diagnostic scan (check engine light) | $60 to $290 |
| CAN bus wiring repair | $190 to $1,275 |
Before you pay
- Ask the shop what test showed this part is the cause, not just that the code appeared.
- Ask for parts and labor listed separately, and for the hours.
- Ask for a written OK before any extra work. Massachusetts rules require written authorization before repairs.
Got a quote already? Check it against the range. Want to see if your car has a recall tied to this problem? Check recalls by VIN.
Need to read a code yourself? OBD-II scanners on eBay (affiliate link, disclosure).
P0117 questions
Can this cause overheating?
The bad reading itself does not heat the engine. The risk is that the computer, thinking the engine is cold, may not warn you well if the engine truly overheats, so watch the dash temperature gauge.
Why does the fan run constantly?
When the computer thinks the engine is hot, or cannot read the sensor, it turns the fan on as a safety measure. A fan that never stops is a common symptom of this code.
Is the sensor easy to replace?
It is usually a small part near the thermostat housing, but some coolant has to be drained to remove it. Labor is small, though the shop should top off and bleed air from the system afterward.
How much does it cost to fix P0117?
The most common fix, coolant temperature sensor replacement, has a typical range of $100 to $260 in Boston. It is an estimate built from parts prices and local labor wages, not a quote. Your car and shop change it.
Related codes
- P0118: Coolant temperature signal too high
- P0128: Engine not warming up fast enough
- P0125: Engine slow to warm up for normal fuel control
More engine codes
Code meaning written in our own words. Some codes mean different things on different makes, so check your scan tool or manual. Not a repair shop, estimates only.