Group 30: Electrical system
Diagnostic Trouble Codes
119
Component description
A magnetically controlled proportional valve (MPROP)
controls the fuel pressure (rail pressure) to ensure that
the correct fuel pressure is retained despite varying
engine speed and loading. Signal from engine control
unit is a PWM signal (pulse width modulated signal).
When the current through the valve is changed, this
affects the fuel flow, which results in changed rail
pressure. The rail pressure sensor senses the pres-
sure and converts the pressure signal to a voltage
which is registered by the engine control unit. If the
current to the valve solenoid rises, the less fuel pres-
sure (rail pressure) is obtained. So if a wire breaks full
fuel flow will be achieved.
Fault tracing
FMI 3 Abnormally high voltage or short
circuit to higher voltage
Possible reason:
•
Short circuit to battery voltage in MPROP nega-
tive cable, pin 2 on MPROP.
Suitable action:
1.
Check cable harness and connectors between
EMS 2 and MPROP.
FMI 4 Abnormally low voltage or short
circuit to lower voltage
Possible reason:
•
Short circuit to battery negative in MPROP posi-
tive wire, pin 1 on MPROP.
Suitable action:
1.
Check cable harness and connectors between
EMS 2 and MPROP.
Note! Only TAD 650, 660, 750, 760 has an engine interface. On
TAD 734 the wiring to the EMS 2 is the same but without any en-
gine interface.
Magnetic proprotional
valve (MPROP)
engine
interface