S80 T6 L6-2.9L Turbo VIN 91 B6294T (2002)
The function of the engine coolant level sensor is to alert the driver if the engine coolant level in the expansion tank is too low.
The sensor is a magnetic reed switch, which is enclosed in a pipe on the bottom of the expansion tank. Around the pipe, on the inside of the expansion
tank is a float. This float contains a magnet. When the engine coolant level is above minimum, the float is too high in the tank to affect the switch.
However if the engine coolant level falls below the minimum level, the magnetic field acts on the switch.
The sensor is supplied with voltage (signal) from the Engine Control Module (ECM) and grounded in chassis. When the engine coolant level in the
expansion tank is over a certain level the circuit closes, which produces a low signal. When the engine coolant level is below a certain level the circuit is
opened by the engine coolant level sensor, which produces a high signal. When the engine control module (ECM) detects a high signal the information
about low engine coolant level is transmitted via the Controller area network (CAN) to the driver information module (DIM), which warns the driver.
Note! There are no functions controlled by the engine which are directly connected to the low coolant level warning lamp. The Engine Control
Module (ECM) only transfers the signal which is used by the Driver Information Module (DIM).
The engine control module (ECM) cannot diagnose the engine coolant level sensor.
Main relay (system relay)
The function of the main relay (system relay) is to supply certain components with voltage.
The relay is mechanical and has a closing function. In the rest position the circuit in the relay is open.
The main relay terminals (#30 and #86) are supplied with voltage by the battery. When the ignition key has been turned and the engine control module
(ECM) is powered, the terminal (#85) on the main relay is grounded by the engine control module (ECM).
