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10.4 Diagnosis
Overall check on EGR operation
To check operation start the engine and let it warm up to 65 deg C or above. Then
race the engine by pressing the accelerator pedal. At this point the diaphragm of the
EGR valve should lift. (Perhaps the EGR valve has to be unbolted first?).
Fail a: EGR and glow control unit
A simple set of test of voltage outputs across various terminals will determine
whether the control unit is working. However they are not practical to describe here
and require the Mitsubishi manual. The EGR control unit senses engine speed,
accelerator position, and engine temperature. Therefore a faulty sensor in any of
these locations could also affect EGR operation. Some tests follow.
Fail a: Accelerator sensor
Check that the sensor for accelerator lever position is working correctly. With the
ignition on (not started) it should read 0.3-1.5 V when idling, and 3.7 - 4.8 when fully
open. Special equipment plus a multi-meter is needed for this test, and the
accelerator cable must be loosened and the engine at operating temperature. Adjust
the sensor position to get within the above range. Turning the sensor clockwise will
decrease the voltage.
Fail a: Engine speed sensor
Disconnect the connectors. The resistance between pins 3 and 6 should be 1.3-1.9 k
ohm. It is recommended that you obtain the Mitsubishi manual.
Fail a: Engine temperature sensor
Remove sensor. The resistance should be 3.3 kohms at 20 deg C and 0.3 kohms at
80 deg C.
Fail b: Harness continuity
A simple set of resistance tests across various terminals will check for electrical
continuity between the control unit and the solenoids.
Fail c: Solenoids holding pressure
A vacuum pump is used to test that each of the two EGR solenoids holds a vacuum
whether energised or not.
Fail c: Solenoids electrical behaviour
The solenoid resistance should be 35-44 ohms for each of the two solenoids (at 20
deg C).
Fail e: EGR valve stuck
No official Mitsubishi repair methods known. However, this comment, which applies
to EGR problems in general, may be helpful:
‘If the EGR valve stem is accessible, push it against spring pressure. It should
move freely and return fully. If not, remove the valve for cleaning or
replacement. With the engine at normal operating temperature, open the
throttle enough to reach at least 2,500 rpm while watching the EGR valve