Replace the engine coolant temperature sensor on the 2016-2021 Honda Civic 1.5L Turbo engine to restore accurate temperature readings and proper engine management.

Warnings

Tools required

Parts

• Engine coolant temperature sensor × 1 — 37870-RBB-003 or equivalent
• Coolant drain plug washer × 1 — Use OEM specification

Fluids

• Honda Type 2 Coolant (Blue) — 1.5 qt

Preparation

1. Ensure engine is completely cold to the touch
2. Park vehicle on level surface and engage parking brake
3. Verify you have the correct replacement sensor for 1.5L turbo engine (different from 2.0L naturally aspirated)
4. Place drain pan under radiator drain plug on driver's side of radiator
5. Remove engine cover by pulling up on four mounting points

Procedure

1. 1

   Drain coolant to below sensor level
   Locate the radiator drain plug on the lower driver's side of the radiator. Slowly turn the drain plug counterclockwise to open and drain approximately 1.5-2 quarts of coolant into the drain pan. The coolant level only needs to drop below the sensor location on the engine block. Close drain plug once coolant level is below the sensor.
   Torque spec

   Coolant Drain Plug15 Nm (11 lb-ft)
2. 2

   Disconnect electrical connector
   Locate the coolant temperature sensor on the driver's side of the engine block, just below the thermostat housing. Press the tab on the electrical connector and pull straight back to disconnect. Do not pull on the wires.
3. 3

   Remove old coolant temperature sensor
   Using a 19mm deep socket and ratchet, turn the sensor counterclockwise to remove it from the engine block. Some residual coolant will drain from the opening. Keep shop towels ready to catch drips. Inspect the sensor threads and sealing washer.
4. 4

   Prepare new sensor
   Verify the new coolant temperature sensor matches the old unit exactly (connector type, thread size, and overall length). Check that the O-ring or sealing washer is properly seated on the new sensor. Do not apply thread sealant; the sensor has a tapered thread design that seals without it.
5. 5

   Install new sensor
   Thread the new coolant temperature sensor into the engine block by hand, turning clockwise until finger-tight. Using the 19mm deep socket, tighten the sensor an additional 1/8 to 1/4 turn past finger-tight. Do not overtighten as this can damage the sensor or crack the aluminum block. Final torque should be snug but not excessive (approximately 15-20 Nm if using a torque wrench).
6. 6

   Reconnect electrical connector
   Push the electrical connector onto the new sensor until it clicks into place. Gently tug on the connector to verify it is fully seated and locked.
7. 7

   Refill cooling system
   Using a funnel, pour Honda Type 2 (blue) coolant into the radiator and/or coolant reservoir until the system is filled to the MAX line on the reservoir. Start with pre-mixed 50/50 coolant or mix concentrated coolant with distilled water. Install the radiator cap.
8. 8

   Bleed cooling system
   Start the engine and let it idle with the heater set to maximum temperature. Monitor the coolant level in the reservoir and add coolant as needed while the engine warms up. Run the engine until the cooling fan cycles on at least once, indicating the thermostat has opened. This ensures air is purged from the system.
   ⚠Monitor engine temperature gauge closely. If temperature rises above normal, shut off engine immediately and allow to cool.

Reassembly

1. Reinstall engine cover by aligning all four mounting points and pressing down firmly until seated
2. Wipe up any spilled coolant from engine bay and components
3. Properly dispose of or store used coolant according to local regulations

Verification

• Check for coolant leaks around the sensor with engine at operating temperature
• Verify engine temperature gauge reads normal operating temperature (halfway point)
• Use a scan tool to confirm coolant temperature sensor reading matches actual engine temperature (should be approximately 185-205°F at normal operating temperature)
• Check coolant level in reservoir after engine cools; top off to MAX line if needed
• Verify no diagnostic trouble codes (DTCs) related to coolant temperature sensor are present

More procedures for this vehicle