MPI <4G1> -
Troubleshooting
13A-74
IDLE SPEED CONTROL (ISC) SERVO (STEPPER
MOTOR)
Measurement Method
1. Disconnect the ISC servo connector, and connect the
special tool (test harness: MB991709) in between. (All
terminals should be connected.)
2. Connect the analyzer special patterns pickup to the ISC
servo-side connector terminal 1, terminal 3, terminal 4
and terminal 6 respectively.
Alternate Method (Test harness not available)
1. Connect the analyzer special patterns pickup to
engine-ECU terminal 4, connection terminal 5, connection
terminal 17, and connection terminal 18 respectively.
Standard Wave Pattern
Observation conditions
Function
Special patterns
Pattern height
High
Pattern selector
Display
Engine condition
When the engine coolant temperature is 20
_
C or below, turn the ignition switch
from OFF to ON (without starting the engine).
While the engine is idling, turn the A/C switch to ON.
Immediately after starting the warm engine
Standard wave pattern
The wave pattern
appears for an
instant, but soon
disappears.
Point B
Coil reverse
electromotive force
(Approx. 3
´
10 V)
Point A
Induced electro-
motive force from
the motor turning
(V)
30
20
10
ISC
servo
control
signal
pattern
Time
Special patterns pickup
Analyzer