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No.
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TECH 1 Display
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Conditions for Checking
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Nominal Value
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Trouble Codes
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Terminal
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30
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ENGINE SPEED
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Engine running at idle speed, operating temperature
Switch off all consumers
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19, 31
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48,49,19
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C 20 XE engine:
C 25 XE engine:
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880 to 1020 rpm
600 to 800 rpm
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Note:
· In the Motronic
M 2.8, trouble code 31 is always set when the ignition is switched ON.
This code can either be displayed on TECH 1 or flashed out by
short-circuiting the diagnostic plug with KM-640 in switch position
"B". When the control unit receives engine speed signals from the
inductive pulse pick-up on starting, trouble code 31 is automatically deleted
and does not remain stored.
If trouble code 31 is not deleted on starting, a fault is
present and trouble-shooting should be commenced.
· Trouble code 19 is
only set if there is a very brief interruption of the engine speed signal at
engine speeds higher than 2000 rpm.
If the interruption is longer and at engine speeds lower than
2000 rpm, the data stream from the control unit to TECH 1 is
interrupted.
Test steps 29 and 30 can be divided into 3 parts
A) Engine does not start, trouble code 31 remains stored
B) Brief engine speed interruption, trouble code 19 may
be stored
C) Engine speed deviates from nominal values, no trouble
code stored
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Notes on Trouble-shooting:
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Nominal Value:
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Cause of Fault:
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A) Engine does not start, trouble code 31 remains stored:
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· Check plug
connection from inductive pulse
pick-up to control unit
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firm connection
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· Loose contact
· Corroded contacts
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Applies to C 20 XE engine only:
· Connect checking
spark plugs to ignition
lead for cylinders 1 and 4
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· Start engine
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Checking spark plug ignites
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If no spark
· Lead interruption
from
- ignition coil L 2 / Ter. 1 to trigger
box K 20 / Ter. 1
- trigger box K 20 Ter. 2 to
control unit K 61 Ter. 1
- ignition coil L2 / Ter. 2 to Ter. 15
- ignition coil to spark plug, cylinder 1
- ignition coil to spark plug, cylinder 4
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Applies to C 25 XE engine only
· Disconnect
injector connection plug Y 7-4
· Connect test lamp
to injector lead Y 7-4
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· Start engine
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Test lamp flashes
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If no injection signal
· Short circuit or
lead interruption from
- fuel pump relay K 68 to control
unit
K 61 / Ter. 37 or injector Y 7-4
- injector 7-4
to control unit K 61 / Ter.
34
|
|
|
· Using multimeter,
check resistance at pulse pick-up plug P 35 / Ter. 1 to Ter. 2
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0.5 to 0.8 k W
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· Pulse pick-up
P 35 defective
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· Check resistance
at pulse pick-up plug P 35 / Ter. 1 to Ter. 3 and Ter. 2 to Ter. 3
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infinite W
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· Short circuit from
- pulse Pick-up P 35 /
Ter. 1 to Ter. 3
- pulse pick-up P 35 /
Ter. 2 to Ter. 3
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Nominal values are attained
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· Segment disc/teeth
corroded
· Metal shavings on
pulse pick-up
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B) Brief engine speed interruption, trouble code 19 may
be stored:
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· as for A)
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as for A)
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· as for A)
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· Check shielding on
inductive
pulse pick-up plug P 35 / Ter. 3
on control unit side to ground.
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0 W
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· Interference
pulses in engine speed
signal lead
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· Check that segment
disc is firmly seated and undamaged
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(removal of oil pan required)
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· Segment disc
loose,
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teeth damaged
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Nominal values are attained
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· Replace pulse
pick-up
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C) Engine speed deviates from nominal values, no trouble code
stored:
· See F0: DATA LIST ,
test step 23 and F5: ACTUATOR TEST , test step 06
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