P0117

Engine Coolant Temperature Sensor 1 Circuit Low

Engine coolant temp sensor Generic OBD-II High

What it means

P0117 means the coolant temperature sensor signal is reading low voltage, which the ECM interprets as an implausibly high coolant temperature. It is almost always an electrical fault — a shorted signal wire or a failed sensor — rather than an actual overheat, and it can throw off fuelling and fan control.

High

Can I keep driving? The engine still runs, but a false hot reading can richen or lean the mixture, run the cooling fans constantly, and cause hard cold starts — get it checked soon.

Real-world scan data

Seen in

1,136

scans in the past year

Found in

0.2%

of scans

0.3%

of scans that found faults

Appears alongside · share of P0117 scans

P0115in 23.0% of scans

P1646in 19.6% of scans

P0118in 19.0% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on
Cooling fans running constantly or coming on early
Hard starting or rough running when cold
Worse fuel economy

Common causes

Most likely first

Coolant temperature sensor signal wire shorted to ground (most common)Likely
Failed coolant temperature sensor reading out of rangeCommon
Corroded or damaged connector at the sensorCommon
Chafed or pinched wiring in the sensor circuitLess often
Faulty ECM (rare)Less often

How to diagnose & fix

Work through it in order

Read the live coolant temperature value — a P0117 typically shows an implausibly high reading or a pegged value.
Inspect the sensor connector and wiring for corrosion, chafing, or a short to ground.
Unplug the sensor and check whether the reading swings the other way; back-probe the signal and ground circuits against spec.
Replace the coolant temperature sensor if the wiring is good, then clear and re-test.
Only suspect the ECM after the sensor and wiring are confirmed good.

FAQ

Quick answers

Is it safe to drive with P0117?+

Short trips are usually fine, but the wrong temperature signal can hurt cold starting and fuel economy and keep the fans running, so fix it soon.

Can I just clear P0117?+

It will come straight back if the sensor or its wiring is shorted. Repair the circuit or replace the sensor first, then clear it.

Read & clear P0117 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX