P0116 Code: Toyota Tacoma (2016-2023) - Causes, Symptoms & Fixes

Recap before we start

• Code: P0116 = Engine Coolant Temperature (ECT) Sensor Range/Performance issue. The PCM/ECU detected an ECT input that is out of expected range or not plausible for the engine’s temperature, or a sensor/wiring fault causing an implausible reading.
• Vehicle focus: Toyota Tacoma, model years 2016–2023.
• Data note: The provided NHTSA data shows no owner complaints and no recalls for this combination. No recalls found in NHTSA database.

CODE MEANING AND SEVERITY

• What P0116 means on a Tacoma: The ECT sensor’s signal is not within the ECU’s expected range/behavior for the current engine temperature. This can occur if the sensor is faulty, the wiring/connector is damaged or corroded, or the thermostat/systems are causing readings that don’t match actual engine temperature. In many scenarios, P0116 can lead to poor idle, hesitation, longer cranking, incorrect fuel trims, and potential drivability issues. It can also contribute to reduced fuel economy or mild performance concerns, though it typically won’t cause immediate engine damage by itself.
• Severity in practical terms: Moderate. Most drivers will notice a CEL and some drivability quirks. If left unresolved, it can cause abnormal fuel mixture and thermal management behavior, potentially affecting emissions readiness and long-term efficiency. It is also a symptom that often points to a fault in the cooling system or sensor circuitry rather than a mechanical failure of the engine.

COMMON CAUSES ON TOYOTA TACOMA

• Faulty ECT sensor: The sensor itself has degraded output, drifted resistance, or non-linear response.
• Wiring harness/connector problems: Damaged, frayed, corroded, or loose harness wiring, or a degraded/oxidized sensor connector causing intermittent or abnormal signal.
• Thermostat issues: A thermostat stuck open or failing may cause a cooler-than-expected engine temperature reading for the actual engine temperature, leading to an apparent out-of-range signal.
• Ground or reference issues: Poor ground or 5V reference supply to the ECT circuit can produce abnormal readings.
• ECU/software calibration or fault: In some cases, software/firmware anomalies or updates can influence sensor interpretation; a dealer/tech may perform reflash or calibration if indicated.
• Coolant condition/level anomalies: Very low or contaminated coolant can indirectly affect sensor readings or thermal behavior, though this is less common as the primary cause.
• Other related sensor interactions: While not common for P0116, issues with related sensors (like the intake air or coolant circuits) can complicate or mask the root cause if not carefully diagnosed.

SYMPTOMS YOU MIGHT NOTICE

• Check Engine Light (CEL) illuminated with P0116 code.
• Engine may run rough, idle instability, or stumble, especially when cold.
• Hard or extended cold-start cranking or longer warm-up times.
• Fluctuating or non-typical temperature gauge behavior (if equipped with a gauge that reflects coolant temp).
• Perceived poor acceleration or hesitation in some driving conditions due to abnormal fuel trims.
• Possible slight decrease in fuel economy until the issue is resolved.
• In some cases, no obvious symptoms beyond the CEL and a marginal temperature reading can occur.

DIAGNOSTIC STEPS

Important: Work methodically from simplest, least invasive checks to more involved tests. Document readings and compare to Toyota service specs.

• Step 1: Verify the code and data

  • Use a capable OBD-II scanner to confirm P0116 and pull freeze-frame data.
  • Check live data: ECT sensor reading (in Celsius/Fahrenheit) as the engine warms from cold to hot; compare to actual engine temperature (you may use an infrared thermometer on the radiator hose or intake manifold surface near the thermostat housing) to gauge plausibility.
  • Note any related codes (P0115, P0117, P0118, etc.) that may guide the fault.

• Step 2: Inspect wiring, connectors, and grounds

  • Visually inspect the ECT sensor connector and wiring for damage, corrosion, or loose pins.
  • Check for signs of wear near hot areas (near the thermostat housing, engine bay harness routing).
  • Inspect the ground points for the ECU/ECT circuit and ensure clean, solid grounds.

• Step 3: Test the ECT sensor and circuit (the exact test method should follow Toyota service data)

  • Confirm 5V reference supply and ground continuity to the ECT sensor from the PCM. Check for voltage drop or intermittent connection.
  • Measure ECT sensor resistance at known temperatures if the service manual provides a resistance vs. temperature chart. Compare readings to spec at specific temperatures (e.g., room temp, warmed engine temp). Note that specs vary by sensor type; use Toyota’s spec.
  • If the sensor resistance is not within spec for any temperature, replace the ECT sensor.
  • If the sensor reads within spec but the PCM data shows inconsistent or implausible readings, consider wiring or PCM issues or a need for ECU software updates.

• Step 4: Assess cooling system operation

  • Check coolant level and condition; ensure proper coolant type and mixture.
  • Monitor engine coolant temperature vs. ambient temperature and road/operating conditions. If the engine warms normally but sensor readings stay out of expected range, focus on sensor/wiring; if the engine temperature rises abnormally fast or the reading doesn’t track actual temperature, consider thermostat operation (see Step 6).
  • Perform a thermostat check (see Step 6) if indicated by readings.

• Step 5: Consider software and updates

  • Check for Toyota/Dealer service bulletins or ECU software updates that address ECT sensor interpretation or related calibration. If an update exists, perform reflashing as recommended.

• Step 6: Evaluate thermostat and cooling system as possible root causes

  • If the actual engine temperature does not align with the sensor reading (e.g., it stays cold/low reading while engine is actually hot), inspect or test the thermostat for sticking open or slow closing.
  • If the thermostat is found faulty, replace it and perform a coolant flush if needed. Re-test P0116 after replacement to confirm resolution.
  • After any thermostat work, ensure the cooling system is properly filled and bled to remove air pockets.

• Step 7: Recheck and confirmation

  • Clear the codes after any repair, drive the vehicle through a representative drive cycle (cold start, steady drive, stop-and-go) to confirm the issue is resolved and no new codes appear.
  • If P0116 recurs, consider a more in-depth wiring harness repair or sensor replacement as needed, and re-evaluate for any intermittent issues.

RELATED CODES

• P0115 Engine Coolant Temperature Sensor Circuit
• P0117 Engine Coolant Temperature Sensor Circuit Low Input
• P0118 Engine Coolant Temperature Sensor Circuit High Input
• Note: These related codes share a similar circuit/thermistor concept; diagnosing the exact fault requires correlating sensor data and possibly the ECU’s interpretation of readings. If you encounter any of these, revisit sensor, wiring, and thermostat conditions.

REPAIR OPTIONS AND COSTS (2025 prices)

Prices are estimates and vary by region, shop, and whether OEM or aftermarket parts are used.

• ECT sensor replacement

  • Parts: Range typically $20–$60
  • Labor: About 0.5–1.0 hour
  • Estimated total: $100–$180 (shop); $60–$120 (parts + DIY if you already own tools and can do the work)

• Thermostat replacement

  • Parts: About $15–$40
  • Labor: ~1.0–2.0 hours
  • Estimated total: $160–$350

• Wiring harness/connector repair or replacement

  • Parts: Generally inexpensive (connectors or pigtails in the $5–$50 range)
  • Labor: 1.0–3.0 hours depending on access and damage
  • Estimated total: $150–$600

• Coolant flush and refill

  • Parts: Coolant ($10–$25)
  • Labor: 0.5–1.0 hour
  • Estimated total: $90–$160

• ECU software update or reflash

  • Parts: Usually none; software service fee
  • Labor: 0.5–1.5 hour
  • Estimated total: $60–$150 (dealer or shop)

• Other potential costs

  • Diagnostic fee: Many shops charge $80–$150 to diagnose; some may waive with a paid repair
  • Miscellaneous: Replacement fasteners or clips if damaged during repair

DIY vs PROFESSIONAL

• DIY considerations

  • Pros: Lower cost; good learning experience; ease of sensor replacement or basic electrical checks if you’re comfortable with basic tools and safety.
  • Cons: Diagnosing P0116 often requires precise measurements (sensor resistance, reference voltages) and careful data interpretation; wiring issues can be subtle and time-consuming; improper work can lead to cooling system leaks or electrical faults.

• When to consider a professional

  • If you’re not confident performing electrical tests, wiring checks, or if the diagnostic flow requires Toyota-specific service data, a professional should handle it.
  • If the shop needs to test sensor circuits with manufacturer-grade tooling or perform ECU reflashes, professional service is advised.

• What to bring to a shop

  • A copy of your scan results showing P0116, freeze-frame data, and any live sensor readings.
  • Records of coolant condition/level, last coolant service, thermostat history, and any related codes.
  • Vehicle mileage and recent driving symptoms.

PREVENTION

• Regular cooling system maintenance: follow Toyota’s intervals for coolant replacement and radiator/thermostat checks; use the recommended coolant specification.
• Inspect electrical connections: periodically inspect the ECT sensor connector for corrosion, dirt, or loose pins; apply dielectric grease if appropriate and reseat firmly.
• Protect wiring: ensure harnesses are routed away from hot surfaces, moving parts, and potential chafing points; repair any damaged insulation promptly.
• Avoid aftermarket or substitute sensors without confirming compatibility; if replacement is needed, use OEM or manufacturer-approved parts.
• Keep software up to date: inquire about ECU/TCM/PCM updates that may address sensor interpretation or failure modes.
• Monitor seasonal and long-term coolant behavior: unusually rapid temperature changes or abnormal engine warm-up can be early signs of cooling system issues that should be addressed before they affect sensor performance.

Recalls/TSBs note

• No recalls found in NHTSA database for this make/model/year based on the provided data.
• No additional TSBs are cited in the provided data. If you want to explore potential aftermarket or manufacturer bulletins beyond the supplied data, a Toyota dealer or official service portal can be consulted.

Disclaimer about data limits

• The diagnostic guide above is designed around general P0116 knowledge and typical Tacoma behavior. The provided data indicates no NHTSA owner complaints or recalls for 2016–2023 Tacoma related to P0116, which limits model-year-specific recall guidance. Always corroborate with official Toyota service information and your vehicle’s specific VIN data.

If you’d like, I can tailor the diagnostic steps to your exact symptoms (e.g., you notice hard starting in the morning or a fluctuating temperature gauge) and help you build a max-2-hour DIY diagnostic checklist.