FMI 5 – Current below normal or open circuit
Fault code explanation: Faulty sensor / Fault in sensor circuit
Fault indication: DCU: Engine warning in DCU display.
CIU: Flash code
Flash code
Electrical fault: 7.8
Value fault: 7.7
Conditions for fault code: The voltage on pin B28 in the engine control unit is less than 0.30 Volt.
Possible reason: Open circuit in the sensor 5 Volt supply.
Open circuit in the sensor signal cable.
Short circuited sensor signal cable to battery negative.
Faulty sensor.
Suitable action: 1 Check the cable harness between the crankcase pressure sensor and
the EMS2.
2 Check the contact pressure in socket 17 and 28 in the engine connector
3 Check the sensor.
Circuit description
The sensor which measures the crankcase pressure
is an
active sensor, i.e. it must have operating voltage.
The engine control unit, connector B, pin 17, supplies
the sensor, pin 1 with +5 Volt. The sensor, pin 4, is
connected to battery negative via the engine control
unit, connector B, pin 18.
The output signal from the pressure sensor, pin 2, to
the engine control unit, connector B, pin 28, is a voltage
signal which is proportional to the crankcase pressure.
It is the velocity of a rising crankcase sure that trigger
the alarm. The output signal is linear within the sensors
working range.
GN / R
a Crankcase pressure
b Connector B
30-2 Fault Tracing
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