System for diagnosing an internal combustion engine

• US 4,534,214 A
• Filed: 09/26/1983
• Issued: 08/13/1985
• Est. Priority Date: 10/01/1982
• Status: Expired due to Fees

• Current Assignee: Fuji Heavy Industries Limited (Subaru Corp.)
• Original Assignee: Fuji Heavy Industries Limited (Subaru Corp.)
• Inventors: Takahashi, Toshio
• Primary Examiner(s): MYRACLE, JERRY
• Application Number:
  US06/535,507
• Time in Patent Office: 687 Days
• Field of Search: 73/116, 73/118, 73/119 R, 340/52 R, 340/52 F, 123/480, 123/494, 374/145
• US Class Current: 73/114.68
• CPC Class Codes: F02D 2041/227 Limping Home, i.e. taking specific engine control measures at abnormal conditions
• CPC Class Codes: F02D 41/222 relating to the failure of sensors or parameter detection devices
• CPC Class Codes: F02D 41/266 the computer being backed-up or assisted by another circuit, e.g. analogue
• CPC Class Codes: G05B 9/02 electric
• CPC Class Codes: G07C 5/0808 Diagnosing performance data testing of vehicles G01M17/00; testing of electrical installation on vehicles G01R31/005

Abstract

A system for diagnosing an internal combustion engine having a coolant temperature sensor. A coolant temperature diagnosing circuit is provided which is responsive to the output voltage of the sensor for producing a signal when the voltage exceeds a predetermined range. A fail-safe signal generating circuit is provided which is responsive to engine speed and to produce fail-safe signals dependent on the engine speed so as to prevent stalling of the engine.

Claims

1. In a system for diagnosing an internal combustion engine having a coolant temperature sensor, the improvement comprising

a coolant temperature diagnosing circuit responsive to output voltage of said coolant temperature sensor for producing an output when said output voltage exceeds a predetermined range;

means for generating an output voltage dependent on engine speed;

a fail-safe signal generating circuit responsive to said output voltage of said means for producing one of fail-safe signals in dependency on said output voltage of said means; and

switch means responsive to said output of said coolant temperature diagnosing circuit for allowing said fail-safe signal to pass.

2. The system for diagnosing an internal combustion engine according to claim 2 wherein said coolant temperature diagnosing circuit comprises a comparator, means for changing the output of said comparator to pulses, and a counter for counting said pulses, said counter being adapted to produce an output when the count reaches a predetermined count.