Volvo TAD650VE Workshop Manual page 75

Group 30: Electrical system
Circuit description
The coolant level in the engine is monitored by a level
switch. Pin B23 on the engine control unit (EMS 2)
provides pin 1 on the level switch with a voltage. Pin 2
on the level switch is connected to battery negative via
pin B10 on the engine control unit.
coolant level
The level switch has two states: On/Off.
The level switch consists of two sections, the actual
switch and a magnetic float which is built into the ex-
pansion tank. The switch senses the position of the
magnetic float. When the coolant level falls, the float
operates the switch and a closed circuit is formed.
Fault tracing
FMI 1 Coolant level is too low
Suitable action:
1. Check coolant level.
2. Bleed coolant water system.
3. If low coolant level check coolant water system for
leakage by a pressure test.
4. Check pressure valve in the coolant cup or try with
another coolant cup.
5. Check wiring to the coolant level switch.
6. Check function of coolant level switch.
FMI 3 Abnormally high voltage or short
circuit to higher voltage has been
detected.
Fault condition:
The voltage on pin B23 in the engine control unit is too
high.
Possible reason:
• Short circuit to battery voltage on pin B23.
Suitable action:
1. Check cable harness and connectors between
coolant level monitor and EMS2.
Diagnostic Trouble Codes
73