Water in fuel

MID 128, PID 97 Water in fuel

splice water in fuel

MID 128: Engine control unit

FMI 0: The sensor value is valid but above the normal working range. FMI 3: The voltage exceeds the normal value or is short circuited to higher voltage. FMI 4: The voltage is less than the normal value or is short circuited to lower voltage.

FMI Fault code explanation

0 Water in fuel 3, 4 Faulty sensor / Faulty monitor circuit

Fault indication

DCU: Engine warning in DCU display CIU: Flash code

Flash code

Electrical fault: 2.9 Value fault: 2.1

Symptom

None

Circuit description

A monitor is located in the water trap under the fuel filter. Its task is to detect whether there is water in the fuel. The monitor senses the resistance between two pins, wich are in contact with the fuel. When there is no water in the fuel, the resistance is very high. If there is any water in the fuel, the resistance falls. At a threshold resistance (water has been detected), the monitor’s output signal (yellow cable) to the engine control unit pin B8 will be pulled down to zero.

Fault tracing

FMI 0 Water in fuel

Conditions for fault code:

Water in the fuel trap has been detected.

Suitable action:

1. Empty the water trap. 2. Check function of water in fuel monitor.

FMI 3

Conditions for fault code:

The voltage signal on B8 is too high.

Possible reason:

• The cable connected to B8 is short circuited to battery voltage.

Suitable action:

1. Check cable harness and connectors between water in fuel monitor and EMS 2.

FMI 4

Conditions for fault code:

The voltage signal on B8 is too low.

Possible reason:

• Short circuit between both cables to the water in fuel monitor. • The cable connected to B8 is short circuited to battery negative.

Suitable action:

1. Check cable harness and connectors between water in fuel monitor and EMS 2.