Symptom: Honda Accord 2.2, the car lit when the ignition switch to the "ON" position, the coolant thermometer indicates the normal position that is the lowest scale line. After starting the engine, the coolant thermometer pointer slowly rises until the upper limit of the coolant thermometer scale, and the actual temperature of the coolant is only 40 ° C to 50 ° C. At this time after the flame, the ignition switch to the "ON" position, the coolant thermometer pointer is still up to the upper limit position.
    Troubleshooting and troubleshooting: Analyze the fault according to the wiring diagram as follows:
    Coolant temperature sensor failure, line fault, coolant thermometer fault.
    Use the usual method to check: Unplug the coolant temperature sensor end of the wire, its direct grounding, open the ignition switch, found coolant thermometer pointer to "H" direction to move, can be determined is the coolant temperature sensor failure.
    The coolant temperature sensor failure is the most common of these failures. Remove the coolant temperature sensor, measure its resistance at 20 ℃, 50 ℃, 100 ℃ were 400Ω, 120Ω and 30Ω, meet the standard value, it should be said that the coolant temperature sensor no problem. For the sake of safety, with a variable potentiometer connected to the coolant temperature sensor wiring side, one end of the ground, open the ignition switch, change the potentiometer resistance, coolant temperature gauge pointer in the middle position, the resistance value of about 600Ω, but The coolant temperature meter pointer rises again. And then change the resistance value so that the coolant thermometer pointer in the middle position, then the resistance value of about 400Ω, but while the coolant thermometer pointer rises again, you can determine the fault in the coolant temperature table itself. Replace the cooling thermometer after troubleshooting.
    The special feature of this fault is that you can not use the commonly used inspection method, that is, the coolant temperature sensor wire directly to the ground, to determine whether the coolant temperature meter is faulty, or coolant temperature sensor is faulty. If the usual method of inspection, you can only determine the fault in the coolant temperature sensor, replace the fault can not be ruled out. This common method can only be used when the coolant temperature table is not indicated or always indicated at the upper limit position. The best way to encounter such failures is to check whether the coolant temperature sensor resistance matches the standard.