Thermostat malfunction detecting system for engine cooling system

  • US 6,679,110 B2
  • Filed: 03/19/2002
  • Issued: 01/20/2004
  • Est. Priority Date: 12/17/1996
  • Status: Expired due to Term
First Claim
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1. A method for detecting a malfunction of an internal combustion engine thermostat provided in a coolant circulating path, said method comprising the steps of;

  • detecting a first, starting temperature of coolant on the coolant circulating path on the engine side of said thermostat at a location spaced from said thermostat upon engine starting;

    determining whether said starting temperature is less than an opening temperature of said thermostat;

    detecting a second engine side coolant temperature at said location spaced from said thermostat during a period in which said thermostat is normally to be closed; and

    diagnosing, when the first temperature, detected upon starting, is lower than said opening temperature, whether said thermostat has an open-malfunction based on the second engine side coolant temperature.

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