The coolant temperature information is conveyed to the instrument panel, through the PCM, from the Engine Coolant Temperature (ECT) gauge sending unit. To test the gauge sending unit, first test the gauge operation to make sure the problem is not in the gauge or gauge wiring. To test the gauge operation, perform the following procedures.
Check the following fuses for battery voltage before testing.
CRV Models: Fuse No. 25 (7.5 amp)
- With the ignition switch OFF , disconnect the yellow/green wire from the ECT gauge sending unit. Then ground it to a place on the engine block (or other known good ground) with a jumper wire.
- Turn the ignition switch to the ON position.
See Figure 1
- Watch the Engine Coolant Temperature (ECT) gauge. It should start moving towards the hot ("H") mark.
- If the pointer does not move at all or moves erratically, check for an open or point of high resistance in the yellow/green wire. If the wire checks out OK, replace the gauge.
If the above steps did not reveal the problem, the test the gauge sending unit as follows:
- Disconnect the yellow/green wire from the ECT gauge sending unit.
- Connect an ohmmeter to the terminal where the yellow/green wire was attached to the sending unit and a good known ground on the engine block.
See Figure 2
- The ECT gauge sending unit resistance should be 137 ohms at a temperature of 133°F (56°C). If the engine is hot and has a temperature of 185-212°F (85-100°C) the ECT gauge sending unit resistance should be 30 ohms-46 ohms.
REMOVAL & INSTALLATION
- Allow the engine to cool below 100°F (37°C) before working on the cooling system.
- Note the anti-theft code and radio presets for the radio.
- Locate the Engine Coolant Temperature (ECT) gauge sending unit located near the thermostat housing on the engine.
- Disconnect the negative battery cable.
- Detach the ECT gauge sending unit electrical connection.
- Drain the engine coolant into a sealable container.
- Remove the ECT gauge sending unit using a pressure switch socket or box-end wrench.
- Use a sensor safe liquid thread sealant to coat the threads before installation.
Using a tape type of sealant may electrically insulate the sensor not allowing the gauge to register.
- Install the new sensor and tighten to 7 ft. lbs. (9 Nm) using a box-end wrench or sending unit pressure switch socket.
- Refill the engine with a 50/50 solution of water and Honda approved or an equivalent coolant.
- Reconnect the negative battery cable.
- Enter the anti-theft code and radio presets for the radio.
- Start the engine, allow it to reach operating temperature and check for leaks.
- Bleed the cooling system to remove air as necessary.