Circuit Description
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The hybrid control module (HCM) controls the coolant pump operation by applying voltage to the coolant pump relay control circuit with an internal solid state device called a driver. When the HCM is commanding the relay ON, the voltage of the control circuit should be high, near 12 volts. When the HCM is commanding the relay OFF, the voltage potential of the control circuit should be low, near 0 volts.
The HCM monitors the relay control circuits for the following conditions:
- Short to ground
- Short to voltage
- An open circuit
If the HCM detects an improper voltage level on the coolant pump control circuit driver circuit, then DTC B3844 will set and the driver will be disabled.