|
Affected Terminals: 15, 16, 17,
33, 34, 35, 14
Possible Trouble Codes: 25, 26,
27, 28, 29, 32, 81, 82, 83, 84, 85, 86
Engine running at idle speed
Engine throttle valve CLOSED
(accelerator pedal in idle
position)
Vehicle stationary
Switch off all consumers
AC switch OFF
Vehicles with AT:
Selector lever in
"P" / "N" position
Press key F8 in the system
main menu, select the desired test using the arrow keys and confirm with YES.
Follow the instructions in the
TECH 1 display.
Note:
In this test mode, TECH 1
freezes the firing angle in the control unit at a fixed value and the idle
speed adjuster to a fixed position. There is no longer any regulation of the
firing angle and idle speed adjuster. it is then possible to switch off the
injectors for the various cylinders.
|
|
|
After the YES key is pressed in
the display on the right, TECH 1 uses the control unit to stabilize the
engine speed at approx. 1200 rpm. After stabilization in the above
range, the idle speed adjuster position is no longer altered and at this
point the actual test can begin. During the stabilization phase, the display on
the right can be seen.
|
INJECTOR
CUTOFF
:
SELECT INJ.
¯:
OFF (3 SECS)
(YES)
|
|
After the stabilization phase,
it is possible to select a cylinder / injector using the arrow key
"UP" and then, with the arrow key "DOWN", to switch
off / deactivate the injector of each selected cylinder for 3 s.
In addition, the YES and NO keys
can be used to display the various data list parameters. Key F9 is used
to store the data as in the snapshot mode.
After fixing the firing angle
and the idle speed adjuster position, i. e. after the actual start of the
test and before deactivating an injector, the engine runs at approx.
1200 rpm. The oxygen sensor control functions normally. The test should
only be started if the cooling fan is not running (otherwise the engine speed
may be approx. 100 rpm lower).
Once an injector is deactivated,
the engine speed sinks by approx. 200 rpm. If the cooling fan starts
running during the deactivation phase, this may lead to a further decrease of
the engine speed of approx. 100 rpm. In this test phase, uncombusted
oyxgen from the deactivated cylinder gains access to the exhaust pipe. This
means that the engine runs lean and therefore that the oxygen sensor for the
cylinder bank in question (oxygen sensor bank 1: cylinders 1, 3, 5; oxygen
sensor bank 2: cylinders 2, 4, 6) constantly displays a voltage lower than
100 mV. The relevant integrator, on the other hand, operates at a
correspondingly higher rate (greater than 128 steps), as the system
attempts to enrichen the mixture.
The above described check should
be performed consecutively for each cylinder. They should all indicate the
same response, i. e. the engine speed should sink by about the same amount
for each cylinder. The purpose of this check is not to test the function of
the injectors, but is intended as a check of the mechanism /
tightness / compression of each individual cylinder.
When this test is completed, the
engine may stall. This may especially be the case if the cooling fan is
running or other consumers are switched on. The snapshot data recorded by
TECH 1 is however retained.
|
WAITING
FOR RPM TO
STABILIZE...
|
