Mitsubishi Montero (2004+). Manual — part 372
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI)
13A-975
INSPECTION PROCEDURE USING AN
OSCILLOSCOPE
M1131154500640
VOLUME AIRFLOW SENSOR
Required Special Tool:
• MB991709: Test Harness
.
Measurement Method
1. Disconnect the volume airflow sensor connector, and
connect the test harness special tool (MB991709) in
between. (All terminals should be connected.)
2. Connect the oscilloscope probe to volume airflow sensor
connector terminal No. 3.
.
Alternate method (Test harness not available)
1. Connect the oscilloscope probe to PCM terminal No. 63.
Standard Wave Pattern
Observation condition
Function
Special pattern
Pattern height
Low
Pattern selector
Display
Engine r/min
Idle speed
Observation condition
Rev engine, observe T1 and T2 remain equal.
AK102975AC
1 2 3 4 5 6 7
VOLUME AIRFLOW
SENSOR CONNECTOR
OSCILLOSCOPE
MB991709
AKX01595
THE TIME (CYCLE TIME) T IS REDUCED WHEN THE
AMOUNT OF INTAKE AIR INCREASES.
TIMES T
1
AND T
2
ARE EQUAL
T
T
1
T
2
10
0
(V)
TIME
AB
Standard wave pattern
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI)
13A-976
Wave Pattern Observation Points
1. Check that cycle time T becomes shorter and the frequency
increases when the engine speed is increased.
.
Examples of Abnormal Wave Patterns
Example 1
Cause of problem
• Sensor interface malfunction.
Wave pattern characteristics
• Rectangular wave pattern is output even when the
engine is not started.
Example 2
Cause of problem
• Damaged rectifier or vortex generation column.
Wave pattern characteristics
• Unstable wave pattern with non-uniform frequency. An
ignition leak will distort the wave pattern temporarily,
even if the volume airflow sensor is normal.
AKX01596
10
0
(V)
T
TIME
AB
Standard wave pattern
AKX01597
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI)
13A-977
CAMSHAFT POSITION SENSOR AND
CRANKSHAFT POSITION SENSOR
Required Special Tools:
• MB991658: Test Harness
• MD998478: Test Harness
.
Measurement Method
1. Disconnect the camshaft position sensor intermediate
connector, and connect the test harness special tool
(MB991658) in between. (All terminals should be
connected.)
2. Connect the oscilloscope probe to camshaft position sensor
intermediate connector terminal No. 2.
3. Disconnect the crankshaft position sensor connector, and
connect the test harness special tool (MD998478) in
between.
4. Connect the oscilloscope probe to crankshaft position
sensor connector terminal No. 2 (black clip of special tool).
.
Alternate method (Test harness not available)
1. Connect the oscilloscope probe to PCM terminal No. 71.
(Check the camshaft position sensor signal wave pattern.)
2. Connect the oscilloscope probe to PCM terminal No. 70.
(Check the crankshaft position sensor signal wave pattern.)
Standard Wave Pattern
Observation condition
Function
Special pattern
Pattern height
Low
Pattern selector
Display
Engine r/min
Idle speed
AK102978AC
CAMSHAFT POSITION
SENSOR INTERMEDIATE
CONNECTOR
MB991658
OSCILLOSCOPE
3
2
1
AK102979AB
MD998478
1 2
3
CRANKSHAFT POSITION
SENSOR CONNECTOR
OSCILLOSCOPE
MULTIPORT FUEL INJECTION (MFI) DIAGNOSIS
TSB Revision
MULTIPORT FUEL INJECTION (MFI)
13A-978
Wave Pattern Observation Points
1. Check that cycle time T becomes shorter when the engine
speed increased.
.
Examples of Abnormal Wave Patterns
Example 1
Cause of problem
• Sensor interface malfunction.
Wave pattern characteristics
• Rectangular wave pattern is output even when the
engine is not started.
Example 2
Cause of problem
• Loose timing belt.
• Abnormality in sensor disc.
Wave pattern characteristics
• Wave pattern is displaced to the left or right.
AKX01600
2 ENGINE REVOLUTIONS (1 CAMSHAFT REVOLUTION)
75
BTDC
5
BTDC
T
CYCLE TIME CHANGES
WITH ENGINE SPEED
CHANGES
CRANKSHAFT
POSITION
SENSOR OUTPUT
WAVE PATTERN
CAMSHAFT
POSITION
SENSOR OUTPUT
WAVE PATTERN
TDC: TOP DEAD CENTER
NO.1 TDC
NO.2 TDC
NO.3 TDC
NO.4 TDC
NO.5 TDC
NO.6 TDC
TIME
Standard wave pattern
AB
AKX01597
AKX01602
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