Output transistor driver diagnostic system

• US 4,538,106 A
• Filed: 06/13/1983
• Issued: 08/27/1985
• Est. Priority Date: 06/13/1983
• Status: Expired due to Fees

• Current Assignee: Ford Motor Company
• Original Assignee: Ford Motor Company
• Inventors: Anderson, Robert L.
• Primary Examiner(s): Karlsen, Ernest F.
• Application Number:
  US06/503,924
• Time in Patent Office: 806 Days
• Field of Search: 324/158 T, 340/635, 340/644, 340/645, 340/514, 361/1, 361/91, 361/92
• US Class Current: 324/762.08
• CPC Class Codes: G01R 31/2608 for testing bipolar transistors

Abstract

An apparatus for diagnosing the operation of a plurality of output transistor drivers includes a plurality of detection transistors, a reference resistor and a voltage detector. Each detection resistor is coupled from a collector of one output transistor driver to a common node. The reference resistor is coupled between the common node and a ground potential. The voltage detector measures voltage across the reference resistor to determine the existence of an improperly functioning transistor. The test method includes turning off all the transistor drivers, detecting the voltage, and comparing the voltage to a reference voltage to determine if any transistors are shorted. If there are no shorts, the transistors are sequentially turned on to determine if any transistors are open.

Claims

1. An apparatus for diagnosing the operation of a plurality of output transistor drivers of an electronic engine control module including:

a plurality of detection resistors, each detection resistor having a magnitude of about 100,000 ohms and being coupled from a collector of one output transistor driver to a common node;

a reference resistor, having a magnitude of about 3000 ohms, coupled between said common node and a ground potential; and

a voltage detector coupled to said common node for measuring voltage to determine whether the voltage is within predetermined limits and thereby to determine the existence of an improperly functioning transistor driver.

2. A method of diagnosing the functioning of a plurality of output transistor drivers of an electronic engine control module including:

connecting a resistor from each collector of each output transistor driver to a common node;

connecting a reference resistor from the common node to a ground potential;

turning off of the output transistor drivers;

measuring a first diagnostic voltage at the common node;

comparing said first diagnostic voltage to an expected voltage value;

concluding at least one output transistor driver is shorted if the measured first diagnostic voltage is outside a first expected voltage value limit;

sequentially turning on each transistor driver;

measuring a second diagnostic voltage at the common node;

comparing said second diagnostic voltage to said first diagnostic voltage;

concluding a turned on transistor is open if said second diagnostic voltage is equal to said first diagnostic voltage;

concluding a turned on transistor is associated with an open load solenoid if said second diagnostic voltage is about 40 to 50 millivolts greater than said first diagnostic voltage; and

displaying the existence of a fault upon concluding there is an open transistor or a shorted transistor.