P0117 – Meaning, Causes, Symptoms, & Fixes

What Does Code P0117 Mean?

• P0117 definition: Engine Coolant Temperature (ECT) Sensor Circuit has lower than normal voltage.
• Issue Severity: SEVERE – Stop driving immediately
• Repair Urgency: Fix this code immediately (same day if possible) to avoid poor engine performance, damage to the engine and emission systems, and overheating.
• Diagnosis: This trouble code will put your vehicle into a failsafe mode, which may cause your car’s engine to hesitate and run rough. Other characteristics of the failsafe mode may include lowered fuel economy, increased emissions, and other driving inconveniences. We recommend getting maintenance immediately as these conditions, if unattended for extended periods of time, may cause further damage to your vehicle.

The engine coolant temperature (ECT) sensor monitors the fluctuations in the temperature of the engine coolant. This data is sent to the ECM, which uses this data to regulate the air to fuel ratio, cooling fans, and ignition spark timing needed by the engine. Code P0117 is the result of the ECT sensor indicating a low input from the coolant temperature circuit.

P0117 Causes

There are many potential causes of code P0117.

• Rusted/Dirty Engine Coolant
• Air Pocket in Coolant System
• Frayed ECT wiring
• Malfunctioning ECT Sensor
• Open ECT circuit
• Faulty ECM

P0117 Symptoms

• Check engine light
• Rough engine performance
• Poor idle quality
• Lower fuel economy
• No noticeable adverse conditions in some cases

How Do I Fix Code P0117?

With an ECT sensor fault, the first step is to get it diagnosed to figure out what is causing the problem. 

If your vehicle has this fault and you’re not comfortable diagnosing this issue at home, we recommend finding a RepairPal certified shop nearby to pinpoint the problem and give an accurate estimate for repairs. 

These shops can not only help you figure out what’s going wrong before you waste time and money on the wrong parts, but they also offer a minimum 12-month, 12,000-mile warranty and stand behind all their estimates with guaranteed fair pricing.

> Find a RepairPal Certified Shop Near You

How Much Does It Cost to Fix Code P0117?

P0117 can be caused by anything from dirty coolant to faulty wiring to a failed ECM. It’s impossible to give an accurate estimate without properly diagnosing the issue first. 

If you take your car to a shop for diagnosis, most shops will start with an hour of “diag time” (the time spent in labor diagnosing your specific issue). Depending on the shop’s labor rate, this typically costs somewhere between $75-$150. Many, if not most, shops will apply this diagnosis fee to any required repairs if you have them perform the repairs for you. From there, a shop will be able to give you an accurate estimate for repairs to fix your P0117 code.

Possible Repair Costs for P0117

For error code P0117, one or more of the below repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to make the repair.

• Engine Coolant Temperature Sensor $140-$200
• Coolant Flush $100-$150
• Wiring repair/replacement $100-$1000
• ECM $1000-$1200

DIY Steps to Diagnose Code P0117

Engine code P0117 could be caused by a number of things, including dirty coolant, faulty wiring, or a faulty ECT sensor. If you’d like to try to fix code P0117 at home without throwing money at parts, you’ll want to follow the steps below for proper diagnosis. Keep in mind that this is an intermediate-level diagnosis and repair and is not recommended for beginners. Diagnosis requires more specialized equipment beyond what the FIXD Sensor can provide and it can be a time and labor-intensive process for inexperienced DIYers.

DIY difficulty level: Intermediate

This repair requires mechanical knowledge and is not recommended for beginners.

Tools/parts needed (our top picks from Amazon):

• FIXD
• Digital multimeter
• A pot of boiling water

STEP 1: USE FIXD TO ENSURE NO OTHER ENGINE CODES ARE PRESENT.

Use FIXD to check if there are any other codes along with P0117.

STEP 2: CHECK COOLANT.

Look inside your radiator and coolant reservoir for air pockets and dirty or rusty coolant. If you find either, flush and bleed the coolant system.

STEP 3: CHECK WIRING.

Disconnect the ECT sensor and check the circuit wiring for fraying or a poor connection. Check the resistance of the wires from the ECT sensor to the ECM. You should have continuity and low resistance. If the test shows an open circuit or high resistance, repair the wiring.

STEP 4: TEST ECT SENSOR.

Remove the coolant temperature sensor and check the resistance of the sensor. At roughly 70°F the resistance should be approximately 2,500 ohms. Place the tip of the sensor (the part that normally sticks into your cooling system) into a pot of boiling water to simulate hot coolant. The resistance should drop dramatically in the higher temperature. Take the sensor out of the boiling water and watch the resistance values. The resistance should go back up as the sensor cools off. 

If your ECT did not meet the above criteria then the sensor is faulty and needs to be replaced. If the sensor passes the above tests, then you may have a wiring issue, or in very rare cases, a faulty ECM.

Common P0117 Diagnosis Mistakes

Prematurely replacing the ECT sensor before attempting to visually inspect the connector and cooling system.

Still Need Help Fixing Code P0117?

If you’ve followed the steps above and are still experiencing check engine code P0117, please contact the FIXD Mechanic Hotline if you’re a FIXD Premium subscriber or find a RepairPal certified shop near you to get the right repairs at a fair price.

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