What does P0117 mean?
The coolant temperature sensor signal voltage is too low — usually a wiring short to ground, a damaged sensor, or a connector issue.
Quick Decision Guide
- Short to ground in ECT signal wire
- Failed coolant temperature sensor
- Damaged ECT connector
When to stop driving
If the temperature gauge reads high, you see steam, or the overheat warning is on, stop driving immediately. Otherwise, P0117 is a sensor circuit fault and not an emergency.
Reviewed by ratchit Automotive Solutions for clarity and inspection-first safety framing. Not a substitute for professional diagnosis.
Repair Decision & Cost Guide
Use this guide to decide what to inspect first, what it may cost, and when to move from DIY checks to professional diagnosis.
P0117 affects warm-up performance — confirm the actual coolant temperature with a scanner before replacing the thermostat or sensor.
DIY vs. Shop
Can you keep driving?
Best first DIY check
Don't replace this first
When to seek a shop
Recommended next action
Estimated Repair Cost
Inspection cost
$0–$25 DIY scanner
Shop diagnostic cost
$80–$150 (typical shop diagnostic fee)
Shop repair cost
$80–$250
Diagnostic uncertainty: This code points to a system or condition, not a guaranteed failed part. Inspect before replacing.
Cost variation: Costs vary by vehicle, location, part quality, labor rate, and the confirmed root cause.
Inspect Before Replacing
These checks are cheap, fast, and rule out the most common causes before spending money on parts.
- 1Confirm with an infrared thermometer that the engine is not actually overheating.
- 2Inspect the ECT connector and visible signal wire for damage or shorts to ground.
Track this cooling issue
Save this issue to My Garage, track what you inspect, and build service history for this vehicle.
V-IQ readiness preview: Medium impact — resolving and tracking this issue may improve your V-IQ readiness. Tracking active codes and resolutions builds a service history we use to estimate V-IQ readiness over time.
Understanding P0117 in detail
P0117 means the ECT sensor's signal voltage is below the ECM's minimum threshold. Because most coolant temperature sensors are negative-temperature-coefficient (NTC) thermistors — resistance drops as temperature rises — a stuck-low signal corresponds to the ECM seeing an absurdly hot reading (often the maximum temperature value the table can represent). This usually triggers cooling fans on continuously and may put the engine in a 'limp' or rich-running state to protect against perceived overheat. Causes are typically a short to ground in the signal wire, a failed sensor reading short internally, or a damaged connector.
Symptoms of P0117
- Check engine light on
- Cooling fans running constantly
- Engine runs rich
- Possible reduced power
- Temperature gauge may read maxed out
Common causes
- Short to ground in ECT signal wire
- Failed coolant temperature sensor
- Damaged ECT connector
How to diagnose P0117
Steps ordered by urgency — tackle Now items first.
- NowConfirm with an infrared thermometer that the engine is not actually overheating.
- NowInspect the ECT connector and visible signal wire for damage or shorts to ground.
- SoonDisconnect the ECT sensor — if the code changes to P0118 (high input), the wiring is good and the sensor is shorting internally.
- LaterReplace the ECT sensor if wiring tests good.
How to fix P0117
Fixes listed in order of likelihood and cost-efficiency.
- 1Repair ECT wiring (short to ground)
- 2Replace coolant temperature sensor
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Recommended tools & parts
These recommendations appear because this issue commonly requires inspection in this system area. ratchit does not recommend replacing parts until the likely cause is confirmed.
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Estimated Repair Cost — P0117
Ranges vary by vehicle, region, and shop. Use as a ballpark — always get a quote.
DIY estimate
$10 – $40
Shop estimate
$80 – $250
DIY estimate
$15 – $50
Shop estimate
$100 – $250
Cost data is estimated and may not reflect your specific vehicle or location.
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Frequently Asked Questions
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