Abstract: A diagnostic system includes a fan control circuit coupled to an electric fan and a microcontroller, and a sense line coupled to the fan control circuit and the microcontroller. The fan control circuit outputs a fan command sense signal at a duty cycle through the sense line to the microcontroller. A tachometer generates a tachometer signal at a frequency indicative of the rotational speed of the electric fan. A fan tachometer circuit receives the tachometer signal and outputs the tachometer sense signal at a frequency to the microcontroller in response to the tachometer signal. The microcontroller sets a second diagnostic flag to an error value indicating that the sense line has impaired operation if the frequency of the tachometer sense signal is within a desired frequency range, and a first diagnostic flag is equal to a first error value.

Abstract: A diagnostic system for a hybrid electric vehicle is provided. The system includes a vehicle controller, a battery management controller, a monitoring circuit, a transistor, a voltage sensor, and an analog-to-digital converter. The vehicle controller sends a first message to the battery management controller indicating an engine crank occurred. The battery management controller sends a second message to the monitoring circuit, and the monitoring circuit induces a transistor to de-energize an electrical relay. The voltage sensor outputs a voltage signal indicative of a voltage being output by the transistor. The analog-to-digital converter outputs a voltage value indicative of the voltage. The battery management controller sets a diagnostic flag to a first non-fault value if the voltage value is less than a threshold voltage value.

Abstract: A diagnostic system for a hybrid electric vehicle is provided. The system includes a vehicle controller, a battery management controller, a monitoring circuit, a transistor, a voltage sensor, and an analog-to-digital converter. The vehicle controller sends a first message to the battery management controller indicating an engine crank occurred. The battery management controller sends a second message to the monitoring circuit, and the monitoring circuit induces a transistor to de-energize an electrical relay. The voltage sensor outputs a voltage signal indicative of a voltage being output by the transistor. The analog-to-digital converter outputs a voltage value indicative of the voltage. The battery management controller sets a diagnostic flag to a first non-fault value if the voltage value is less than a threshold voltage value.

Abstract: A diagnostic system includes a fan control circuit coupled to an electric fan and a microcontroller, and a sense line coupled to the fan control circuit and the microcontroller. The fan control circuit outputs a fan command sense signal at a duty cycle through the sense line to the microcontroller. A tachometer generates a tachometer signal at a frequency indicative of the rotational speed of the electric fan. A fan tachometer circuit receives the tachometer signal and outputs the tachometer sense signal at a frequency to the microcontroller in response to the tachometer signal. The microcontroller sets a second diagnostic flag to an error value indicating that the sense line has impaired operation if the frequency of the tachometer sense signal is within a desired frequency range, and a first diagnostic flag is equal to a first error value.