METHOD OF DIAGNOSING A LOW RANGE LIMITING MALFUNCTION OF AN ENGINE COOLANT TEMPERATURE SENSOR

• US 20070073509A1
• Filed: 09/23/2005
• Published: 03/29/2007
• Est. Priority Date: 09/23/2005
• Status: Active Grant

• Current Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Rahman, Mahfuzur, Simpson, Kenneth
• Granted Patent: US 7,203,617 B1
• Time in Patent Office: Days
• US Class Current: 702/130
• CPC Class Codes: G01K 15/00 Testing or calibrating of thermometers
• CPC Class Codes: G01K 2205/00 Application of thermometers in motors, e.g. of a vehicle

Abstract

Low range limiting malfunctions of an engine coolant temperature (ECT) sensor are diagnosed by comparing a change in the sensed temperature during engine operation with a calibrated temperature change. If the change in sensed temperature fails to exceed the calibrated temperature change, and a diagnostic for detecting a stuck ECT signal is either inconclusive or passed, a low range limiting malfunction of the sensor is indicated. If the diagnostic for detecting a stuck ECT signal is failed, the low range limiting diagnostic concludes with no report even if the change in sensed temperature fails to exceed the calibrated temperature change.

Claims

1. A method of diagnosing low range limiting malfunctions of an engine coolant temperature sensor, comprising the steps of:

sampling a first value of a signal produced by said sensor at an initiation of engine operation;

sampling a second value of the signal produced by said sensor following an interval of engine operation;

computing a temperature difference between said first and second values;

periodically sampling said signal during an initial diagnostic interval to detect a stuck condition of said sensor;

reporting an absence of low range limiting malfunctions if the computed temperature difference exceeds a calibrated temperature difference; and

reporting a low range limiting malfunction if the computed temperature difference is less than said calibrated temperature difference and a stuck condition of said sensor is not detected during said initial diagnostic interval.

2. The method of claim 1, including the step of:

reporting that the diagnosing of low range limiting malfunctions is inconclusive if the computed temperature difference is less than said calibrated temperature difference and a stuck condition of said sensor is detected during said initial diagnostic interval.

3. The method of claim 1, including the steps of:

determining an ambient air temperature at the initiation of engine operation; and

reporting that the diagnosing of low range limiting malfunctions is inconclusive if the determined ambient air temperature exceeds a calibrated temperature.

4. The method of claim 3, including the steps of:

measuring a flow of intake air of said engine and a temperature of said intake air; and

determining the ambient air temperature according to the measured temperature of intake air when the measured flow of intake air continuously exceeds a calibrated flow for at least a calibrated interval.

5. The method of claim 1, including the step of:

reporting that the diagnosing of low range limiting malfunctions is inconclusive if the signal produced by said sensor is out of range.

6. The method of claim 1, including the step of:

reporting that the diagnosing of low range limiting malfunctions is inconclusive if a soak time of said engine prior to said initiation of engine operation is less than a calibrated time.