Checking with Diagnostic Switch KM-640
Diagnostic Switch, Connect
For this, the switch is turned to position "B" and connected to the diagnostic plug (ALDL plug) in the engine compartment.
Trouble Code Readout with Diagnostic Switch KM-640
The excitation line of the Multec control unit is short-circuited to ground with KM-640 in the diagnostic switch.
This triggers blink code output with the ignition switched on. Any trouble codes that may be present are now displayed via the engine telltale.
Important Note
If the customer reports that the engine telltale illuminated while travelling, and it remains out in the workshop, fault no. 3 is present. I.e. the actual fault is on certain circumstances still present, as the conditions for setting (see Table 2) have been fulfilled, but the fault can no longer be recognized, because the conditions have changed so much that they no longer correspond to the conditions described in Table 2.
See also remedy in 5.1.7.2.
Service Mode with Diagnostic Switch KM-640
The service mode is active when the engine is running and Diagnostic Switch KM-640 is connected to the ALDL plug and turned to position "B". This mode is not supported by TECH 1.
Operating Method: 1.If the oxygen loop is not yet closed, the engine telltale flashes at a frequency of 2 Hz.
!! Use only 2.If the oxygen loop is closed, the engine telltale is closed in case the control unit at
if no TECH 1 the input "oxygen sensor voltage" has registered a voltage change from lean to rich
is available or from rich to lean within the last seconds.
3.If no voltage change has taken place at the oxygen sensor within the last seconds, the present actual mixture condition is displayed.
I.e. rich mixture = engine telltale "ON"
lean mixture = engine telltale "OFF"
Observation: In the service mode, the idle engine speed is increased to 1000 rpm and the firing angle adjusted to 10° CA BTDC.
If the control unit registers a fault in the service mode, it is not filed in the fault memory.