P0116 Code: Honda Accord (2018-2023) - Causes, Symptoms & Fixes

Comprehensive diagnostic guide for OBD-II code P0116 on 2018–2023 Honda Accord

Reality check from the provided NHTSA data

• Complaints: No NHTSA complaints found for this make/model/year/issue combination.
• Recalls: No recalls found in NHTSA database.
• What this means: There is no specific NHTSA complaint or recall data to guide fixes for P0116 on the 2018–2023 Accord in the supplied dataset. The diagnostic guidance below blends typical Honda practices with general automotive knowledge. Always verify with the latest service information for your exact VIN and engine type.

CODE MEANING AND SEVERITY

• Code meaning: P0116 – Engine Coolant Temperature Sensor Range/Performance. The PCM (engine computer) detected that the engine coolant temperature (ECT) sensor reading is out of the expected range or the sensor circuit is not performing within spec.
• What it implies on a Honda Accord: The ECT sensor (often a two-wire NTC device located near the thermostat housing or embedded in or near the thermostat assembly) is reporting a coolant temperature that the PCM considers out of range given actual operating conditions. This can be due to a faulty sensor, bad wiring/connector, thermostat or cooling system issues, or, less commonly, PCM fault.
• Severity: Moderate. If the reading is truly out of range, it can cause rich/lean fuel trim errors, poor drivability, longer warm-up, reduced fuel economy, and potential catalyst or emissions concerns. If the actual coolant temperature is genuinely out of spec (e.g., excessively high), the engine could risk overheating if the condition is not corrected. Treat as a potentially consequential issue and diagnose to confirm sensor health and cooling-system integrity.

COMMON CAUSES ON HONDA ACCORD (2018–2023)

• Faulty ECT sensor: Most common cause; sensor has failed or drifted out of spec.
• Damaged or corroded wiring/connector: Faulty connection or frayed wiring between the ECT sensor and PCM.
• Coolant issues: Low coolant, contaminated coolant, or air in the cooling system causing readings to appear out of range.
• Thermostat issues: Stuck-open or stuck-closed thermostat altering actual coolant temperature, which can stress sensor readings or present conflicting data to the PCM.
• Cooling-system problems: Leaks, failed radiator cap, water pump issues, or blocked passages can cause abnormal temperature behavior.
• PCM/ECU data error: Rare, but possible; usually ruled out after basic electrical checks.
• Model-specific note: Some Accord engines use an ECT sensor integrated with or closely tied to the thermostat housing; replacement may involve the housing assembly on certain configurations. Location can vary by engine (e.g., 1.5L turbo vs. 2.0L turbo); always check the service manual for exact location and torque specs.

SYMPTOMS (POSSIBLE)

• Check Engine Light (CEL) or Malfunction Indicator Light on.
• Irregular or no heat at heater controls (heater performance tied to coolant temp behavior).
• Poor or fluctuating idle, hesitation, or rough running.
• Worsened or inconsistent fuel economy; erratic or delayed PCM fueling adjustments.
• Longer warm-up time or engine running cooler than expected in cool ambient conditions (or, conversely, readings suggesting overheating when the actual temp is not that high).
• In some cases, no obvious symptoms other than the MIL.

DIAGNOSTIC STEPS (structured approach)

Note: Always start with the simplest/cheapest checks and move to more involved tests. Document live data from a reliable OBD-II scan tool.

A. Prepare and confirm

• Retrieve DTCs with a scanner. Confirm P0116 is present and note any related codes (P0115, P0117, P0118, P0125, P0128, etc.).
• Review Freeze Frame data: look at coolant temperature, engine load, RPM, and vehicle speed at the time the code was set.

B. Check obvious physical conditions

• Inspect coolant level and condition. Look for signs of leaks, contamination, or signs of coolant mixing (milky/oily signs).
• Check for air in the cooling system and verify it has been properly bled after any service.
• Inspect cooling-system components: radiator hoses, clamps, thermostat housing, radiator cap, water pump, and any recent cooling-system service.
• Visual inspection of the ECT sensor and its connector for corrosion, damage, bent pins, or loose fit.

C. Compare sensor data to real temperature

• With the engine running (and cooled down if safe), read live data values for:
  • Engine Coolant Temperature (ECT) sensor reading from the PCM.
  • Actual coolant temperature if an infrared thermometer reading is feasible (skin-level check on accessible coolant outlet or radiator inlet, not a perfect substitute but useful for a sanity check when safe).
  • Ambient temperature reading (if available) to see if the sensor is reacting plausibly to ambient conditions.
• If the ECT reading is wildly different from the actual coolant temperature, suspect sensor or circuit issues.

D. Electrical tests (sensor circuit)

• Inspect the ECT sensor circuit wire harness for continuity and resistance vs. temperature (NTC behavior). Check:
  • Signal wire continuity (PCM-to-sensor) for opens.
  • Ground continuity for the sensor ground.
  • No short to battery voltage on the signal wire (would indicate a short to power).
• Check the connector pins for corrosion or damage; reseat the connector.

E. Sensor resistance test (typical, general method)

• With the key off, disconnect the ECT sensor.
• Measure resistance across the sensor terminals with a digital multimeter.
• Compare measured resistance to the expected resistance vs temperature (you will need the service data/specs for your exact Accord engine). A sensor that reads out of spec or shows no resistance change with temperature is suspect.
• Notes:
  • Honda service data will provide the exact resistance vs temperature table for the specific ECT sensor used on your engine; use that as your reference.
  • If you don’t have the exact spec, an out-of-range or non-responsive sensor generally warrants replacement.

F. If sensor and wiring tests pass, assess cooling system operation

• Thermostat function: A thermostat stuck open or closed can cause temperature readings to misalign with actual coolant temperature. If the thermostat is suspected, test or replace as needed.
• Pressure test: Perform a cooling-system pressure test to check for leaks that might cause inconsistent readings.
• Coolant flush if coolant is degraded or contaminated (after completion, recheck readings).

G. Decide on repair path

• If the ECT sensor shows out-of-range resistance or the live data shows implausible sensor temperatures, replace the ECT sensor.
• If wiring/connectors show damage or poor connection, repair/replace the wiring or connector.
• If coolant system issues (low coolant, air in system, thermostat fault) are evident, address those first; resolve any cooling-system problems and recheck.
• If all else checks out but readings are still out of spec, consider PCM-related checks or reflash only after confirming all hardware issues are addressed.

H. Clear codes and verify

• After repairs, clear the codes and run the vehicle through a steady drive cycle to confirm the code does not return and that the sensor readings behave as expected.

RELATED CODES

• P0115 – Engine Coolant Temperature Sensor Circuit Malfunction
• P0117 – Engine Coolant Temperature Sensor Circuit Low Input
• P0118 – Engine Coolant Temperature Sensor Circuit High Input
• P0125 – Insufficient Coolant Temperature for Closed Loop
• P0128 – Coolant Temperature Below Thermostat Regulating Temperature
  Note: These related codes point to sensor circuitry, temperature ranges, or thermostat behavior and may appear together if the cooling system or sensor is faulty.

REPAIR OPTIONS AND COSTS (2025 prices, ballpark ranges)

Prices vary by market, shop, engine variant (1.5L vs 2.0L), and whether the ECT is mounted with the thermostat housing. All estimates are rough ranges intended for planning; actual quotes will differ.

• ECT sensor replacement

  • Parts: $15–$60
  • Labor: 0.5–1.0 hours
  • Typical total: $60–$150

• Thermostat replacement (if the thermostat needs replacement or is integrated with the housing)

  • Parts: $15–$100
  • Labor: 1.0–2.0 hours
  • Typical total: $150–$350

• Thermostat housing assembly (if required to replace with ECT in the same unit)

  • Parts: $40–$180
  • Labor: 1.0–2.0 hours
  • Typical total: $180–$420

• Cooling-system service (flush/refill with Honda-approved coolant)

  • Parts: $10–$25 (coolant)
  • Labor: 0.5–1.0 hour
  • Typical total: $60–$140

• Wiring/connector repair (if harness damage is found)

  • Parts: $10–$100 (depending on harness repair)
  • Labor: 1.0–2.0 hours
  • Typical total: $120–$350

• PCM/ECU reflash or recalibration (rare; only after hardware issues are resolved)

  • Parts: nominal (no parts if reflashing)
  • Labor: 0.5–1.0 hour
  • Typical total: $50–$150

• Total project examples

  • ECT sensor replacement alone: roughly $60–$150
  • ECT sensor + thermostat/housing: roughly $250–$600
  • Sensor issue with wiring repair: roughly $150–$350

Note: If the issue is intermittent or subtle, some shops may perform a coolant-system bleed, perform a leak test, or replace the sensor as a preventive measure, which could affect final pricing. Always obtain a detailed, itemized quote.

DIY vs PROFESSIONAL

• DIY-friendly tasks (generally suitable for a confident hobbyist):
  • Replacing the ECT sensor (often straightforward on many Honda engines). Steps typically include:
    • Let engine cool, disconnect battery negative cable.
    • Locate the ECT sensor near the thermostat housing.
    • Disconnect the electrical connector, remove the sensor with the appropriate tool, install the new sensor, and torque to spec.
    • Reconnect wiring, refill coolant if drained, and run engine to bleed air.
  • Basic wiring inspection (visual check, connector reseating, cleaning corrosion).
• DIY caveats:
  • Work around hot cooling system can cause burns; ensure engine is cool.
  • Use correct coolant and if you drain coolant, dispose of old coolant properly.
  • Always follow the Honda service manual for torque specs and sensor replacement procedures.
• Professional service:
  • Recommended if:
    • The ECT sensor is integrated with the thermostat housing and requires more extensive disassembly.
    • The cooling system shows signs of leaks or you suspect air in the system.
    • You’re seeing inconsistent live data or a PCM miscalibration after sensor replacement.
    • Wiring inspections require specialized tools or harness repair.
  • Pros can also perform a system leak test, pressure test, and a proper bleed to prevent air pockets.

PREVENTION

• Regular cooling-system maintenance
  • Use the correct Honda-approved coolant. Maintain coolant level between the min/max marks when the engine is cold.
  • Follow the manufacturer’s recommended service interval for coolant replacement or flushing (often in the 5–10 year or 60k–100k mile range depending on model and coolant type; check your owner’s manual and service data).
  • Keep the cooling system free of leaks; promptly address any signs of coolant loss or green/blue coolant staining.
• Sensor and electrical health
  • Periodically inspect the ECT sensor and its connector for corrosion or damage, especially after minor cooling-system or engine work.
  • Address any wiring harness chafing or compromised insulation early.
• Driving habits
  • Avoid prolonged high-speed driving with a poorly functioning cooling system; overheating can cause sensor readings to drift and PCM behavior to be erratic.
  • Ensure the thermostat and radiator are in good condition; a healthy cooling system helps prevent false readings and reduces wear on the sensor.
• Documentation
  • Keep a repair log for coolant system service, sensor replacements, and any related electrical work. This helps technicians diagnose recurring P0116 issues and prevents unnecessary part changes.
• Monitoring
  • If you have an advanced scan tool, monitor live ECT readings during operation (idle, light load, and high engine loads) and flag readings that seem out of spec for your engine’s operating conditions.

Important data caveats

• The provided data shows no NHTSA complaints or recalls for this issue on 2018–2023 Honda Accord in the supplied dataset. This means the diagnostic guidance above is not anchored to a reported NHTSA pattern for this exact model/year and should be treated as general diagnostic insight with typical Honda engineering expectations.
• Real-world fixes rely on VIN-specific details (engine variant, thermostat housing design, sensor part numbers, and service bulletins). If you have access to Honda service information (NWD, TSBs, or VIN-based bulletins), use those sources to refine the approach.
• If you’re using this guide for shop work or a customer handout, consider including a disclaimer that prices, parts, and procedures can vary by region and model year, and that a proper diagnostic should be performed to confirm the fault before replacing components.

Bottom line

• P0116 on a 2018–2023 Honda Accord indicates the ECT sensor reading or circuit is outside of expected range. Start with a thorough check of the sensor, its wiring/connectors, and the cooling system (coolant level, bleed, and thermostat condition). Use live data to compare actual coolant temperature with sensor readings and ambient conditions. Replace the ECT sensor if it tests out of spec or the wiring is damaged, and address the cooling-system issues if indicated. If in doubt, consult a qualified technician who can perform a VIN-specific diagnosis and confirm whether any service bulletins or updates apply to your vehicle.