Circuit/System Description
The engine control module (ECM) commands the fans ON in either high speed or low speed, depending on cooling requirements. In low speed, the fans are configured in series. In high speed, the fans are configured in parallel.
In low speed operation, the ECM applies ground to the coil side of the fan low relay. Voltage is applied directly to the left cooling fan through the switch side of the fan low relay, which is fed by the fan 1 fuse. The right fan is connected in series to the left fan through the de-energized fan control relay so that both operate at low speed.
In high speed operation, the ECM applies a ground to the coil side of the fan low relay, the fan control relay, and the fan high relay. Voltage is applied directly to the right cooling fan through the switch side of the relay, which is fed by the fan 2 fuse. The left cooling fan obtains voltage through the fan low relay and ground through the fan control relay.
The ECM monitors the low and high speed cooling fan relay control circuits for the following conditions
- Short to ground
- Short to voltage
- An open circuit
If the ECM detects an improper voltage level on the low or high speed ECM driver circuits, then DTC P0480 or P0481 will set and the affected ECM driver will be disabled.
The low engine coolant level indicator is controlled by the engine control module (ECM). The normal state of the engine coolant level switch is closed when in contact with coolant.
The engine control module (ECM) commands the fans ON in either high speed or low speed, depending on cooling requirements. In low speed, both fans are turned ON at a reduced speed. High speed has both fans turned ON at full speed.
In low speed operation, the ECM applies ground to the coil side of the fan low relay. This energizes the coil and applies voltage directly to the left cooling fan through the switch side of the fan low relay, which is fed by the fan 1 fuse. The right fan is connected in series to the left fan through the de-energized fan control relay so that both operate at low speed.
In high speed operation, the ECM applies a ground to the coil side of the fan low relay, the fan control relay, and the fan high relay. On the fan high relay, the energized coil closes the switch side of the relay and applies voltage directly to the right cooling fan through the switch side of the relay, which is fed by the fan 2 fuse. At the same time, the ECM energizes fan control relay pulling the switch side over, providing a direct path to ground for the left cooling fan, which has voltage applied through the energized fan low relay. In high speed mode, the fans are operated as a parallel circuit with full voltage applied to each.
The engine control module (ECM) commands the fans ON in either high speed or low speed, depending on cooling requirements. In low speed, both fans are turned ON at a reduced speed. High speed has both fans turned ON at full speed.
In low speed operation, the ECM applies ground to the coil side of the fan low relay. This energizes the coil and applies voltage directly to the left cooling fan through the switch side of the fan low relay, which is fed by the fan 1 fuse. The right fan is connected in series to the left fan through the de-energized series/parallel relay, which is the fan control relay so that both operate at low speed.
In high speed operation, the ECM applies a ground to the coil side of the fan low relay, the fan control relay, and the fan high relay. On the fan high relay, the energized coil closes the switch side of the relay and applies voltage directly to the right cooling fan through the switch side of the relay, which is fed by the fan 2 fuse. At the same time, the ECM energizes fan control relay pulling the switch side over, providing a direct path to ground for the left cooling fan, which has voltage applied through the energized fan low relay. In high speed mode, the fans are operated as a parallel circuit with full voltage applied to each.
The optional coolant heater operates using 110 volt AC external power and is designed to warm the coolant in the engine block area for improved starting in very cold weather. There is an internal thermal switch in the power cord that prevents operation above -18°C (0°F). The coolant heater helps reduce fuel consumption when a cold engine is warming up. The unit is equipped with a detachable AC power cord. A weather shield on the cord is provided to protect the plug when not in use.
Reference Information
Electrical Information Reference
- «Circuit Testing»(ref-278019-S01379251932008012100000)
- «Connector Repairs»(ref-278019-S06982211772008012100000)
- «Testing for Intermittent Conditions and Poor Connections»(ref-278019-S21810776732008012100000)
- «Wiring Repairs»(ref-278019-S25320832652008012100000)
The optional coolant heater operates using 110 volt AC external power and is designed to warm the coolant in the engine block area for improved starting in very cold weather. There are two heater cords available. One has an internal thermal switch in the power cord that prevents operation above -18°C (0°F) and the other operates at all temperatures. A weather shield on the cord is provided to protect the plug when not in use.