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P0117 on Toyota Highlander

Engine Coolant Temperature Sensor 1 Circuit Low

Factory diagnostic protocol and troubleshooting wire for fault code P0117 specifically for the Toyota Highlander (2020–2026, 2.4L Turbo 4-Cyl (T24A-FTS 265HP) / 3.5L V6 / 2.5L Hybrid).

Verified OEM Telemetry & Field Repair Tree
Toyota Highlander2020–2026
Toyota Highlander
SUV2.4L Turbo 4-Cyl (T24A-FTS 265HP) / 3.5L V6 / 2.5L Hybrid
Reliability
Sensor Voltage Ref
0.1V – 5.0V Ref
Highlander SAE Mode $01
ECU Network Bus
500 kbps CAN-FD
ISO 15765-4 Compliant
Drivability Status
Not Recommended
High urgency level
Est. Repair Cost
$80 - $250 (DIY: $20 - $60)
Parts & Labor DIY
Check P0117 On Another Toyota Model:
Diagnose P0117 on Specific Highlander Model Year:

1. Symptoms of P0117 on Toyota Highlander

When the Engine Control Module (ECM/PCM) on your Toyota Highlander (2.4L Turbo 4-Cyl (T24A-FTS 265HP) / 3.5L V6 / 2.5L Hybrid) logs fault code P0117, drivers commonly observe:

Check Engine Light on on Toyota Highlander (2.4L Turbo 4-Cyl (T24A-FTS 265HP) / 3.5L V6 / 2.5L Hybrid)
Radiator radiator fans running constantly at high speed on Toyota Highlander (2.4L Turbo 4-Cyl (T24A-FTS 265HP) / 3.5L V6 / 2.5L Hybrid)
Temperature gauge pegged at maximum H or not reading on Toyota Highlander (2.4L Turbo 4-Cyl (T24A-FTS 265HP) / 3.5L V6 / 2.5L Hybrid)
Engine hard starting when cold (flooding from excess fuel) on Toyota Highlander (2.4L Turbo 4-Cyl (T24A-FTS 265HP) / 3.5L V6 / 2.5L Hybrid)
Poor gas mileage and rough idling on Toyota Highlander (2.4L Turbo 4-Cyl (T24A-FTS 265HP) / 3.5L V6 / 2.5L Hybrid)
Toyota Highlander OBD-II Port Location
The 16-pin diagnostic connector is located Under driver steering column near kick panel. Plug in your scan tool to verify freeze-frame sensor values.

2. Most Likely Causes on Toyota Highlander

Historical warranty claims and technical repair bulletins for Toyota Highlander point to the following failure distribution:

55%
ECT sensor internal short to ground (Toyota OEM Part)
25%
Short circuit to ground in ECT signal wiring harness (Toyota OEM Part)
12%
Damaged, corroded, or water-contaminated ECT connector (Toyota OEM Part)
8%
Faulty PCM / ECM analog input circuit (Toyota OEM Part)
* Source: Synthesized from NHTSA ODI field repair telemetry and verified OEM Technical Service Bulletin (TSB) repair tree frequency percentiles for Toyota Highlander.

3. Step-by-Step DIY Repair Guide for Toyota Highlander

01
Scan ECT Temperature Data

Read ECT live PID on scanner. If it reads 284°F (140°C) or higher with engine cold, a short to ground exists. on the Toyota Highlander equipped with 2.4L Turbo 4-Cyl (T24A-FTS 265HP) / 3.5L V6 / 2.5L Hybrid.

Required Tool: OBD-II Scanner
02
Unplug ECT Sensor Connector

Unplug sensor connector while watching live data. If temperature drops to -40°F (-40°C), the sensor itself is shorted. on the Toyota Highlander equipped with 2.4L Turbo 4-Cyl (T24A-FTS 265HP) / 3.5L V6 / 2.5L Hybrid.

Required Tool: OBD-II Scanner
03
Inspect Wiring Harness

If reading stays pegged at max with sensor unplugged, inspect harness for pinch points grounding against engine block. on the Toyota Highlander equipped with 2.4L Turbo 4-Cyl (T24A-FTS 265HP) / 3.5L V6 / 2.5L Hybrid.

Required Tool: Digital Multimeter
04
Replace Engine Coolant Temperature Sensor

Allow engine to cool, unscrew old ECT sensor from coolant crossover pipe or thermostat housing, install new OEM sensor with fresh thread sealant. on the Toyota Highlander equipped with 2.4L Turbo 4-Cyl (T24A-FTS 265HP) / 3.5L V6 / 2.5L Hybrid.

Required Tool: 19mm Deep Socket, Ratchet, Coolant Catch Pan
05
Top off Coolant & Clear Codes

Bleed air from cooling system, clear DTCs, and verify normal temperature rise on live data. on the Toyota Highlander equipped with 2.4L Turbo 4-Cyl (T24A-FTS 265HP) / 3.5L V6 / 2.5L Hybrid.

Required Tool: Coolant Funnel Kit, OBD-II Scanner
Recommended Parts & Testing Tools

Equipment for Diagnosing Toyota Highlander (P0117)

Prime Fast Delivery & Verified Fitment
Variable Valve Timing (VVT)

VVT Oil Control Solenoid Valve

4.6 / 5.0 (Direct Fit)

Restores accurate camshaft timing and oil pressure regulation on Toyota Highlander.

$34 – $65 Prime
Check Fitment on Amazon
Sensor Signal Voltage Meter

AstroAI Auto-Ranging Digital Multimeter

4.6 / 5.0 (Best Seller)

Essential for testing 0.1V–5.0V sensor reference signals, ground continuity (<0.20Ω), and harness resistance.

$29.99 Prime
View on Amazon
Top Mobile OBD-II Scanner

BlueDriver Bluetooth Pro OBDII Scan Tool

4.7 / 5.0 (50,000+ Reviews)

Reads and clears enhanced codes (ABS, Airbag, Transmission, Engine) & live freeze-frame telemetry on phone.

Compare OEM & Aftermarket Replacement Sensors for Toyota HighlanderVerified direct-fit pricing from Denso, Bosch, Motorcraft, and ACDelco on Amazon.
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Other Common Fault Codes on Toyota Highlander

Frequently diagnosed powertrain, emissions, and sensor trouble codes logged on the Toyota Highlander:

4. Toyota Highlander P0117 FAQs

What causes code P0117 to trigger on a Toyota Highlander?

On the Toyota Highlander (2.4L Turbo 4-Cyl (T24A-FTS 265HP) / 3.5L V6 / 2.5L Hybrid), P0117 is most frequently caused by ECT sensor internal short to ground or Short circuit to ground in ECT signal wiring harness.

Where is the OBD-II port located on my Toyota Highlander?

On the Toyota Highlander, the 16-pin DLC diagnostic connector is located Under driver steering column near kick panel. Plug in any standard OBD-II scanner with the ignition in the ON position to read freeze-frame parameters.

Can I safely drive my Toyota Highlander with code P0117?

No. The ECU thinks the engine is at 280°F+ (overheating) and runs rich or disables cooling fan logic. Given that P0117 carries a High severity rating, we advise avoiding heavy towing or aggressive throttle inputs until sensor readings are verified.