If No Diagnosis Is Possible
NO DIAGNOSIS POSSIBLEIf the System Tester 9288 cannot enter the diagnosis, check the following Items:
NOTE: If the DME relay Is faulty, no diagnosis Is possible (engine cannot run). Power Is supplied to some control units of the diagnosable systems via the DME relay.
Connector at tester
^ Check adapter cable 9288/1 for continuity
Check K and L wires to adapter lead 9288/1 for continuity. Socket 3 (8-pin connector) to pin 7 (19-pin socket). Socket 7 (8-pin connector) to pin 8 (19-pin socket).
Socket 3 = L lead
Socket 8 = K lead
Connector at tester
^ Check power supply
Check ground and terminal 15 of adapter cable 9288/1 for power supply.
Socket 4 = Ground
Socket 5 = Terminal 15
^ Check K and L leads with oscilloscope and Special Tool 9540
Checking the L lead:
Disconnect connector 2 (yellow) from alarm control unit. Connect Special Tool 9540 between alarm control unit and connector 2. Connect oscilloscope to Special Tool 9540, socket 14 (L lead). Check L lead, turning ignition on and switching System Tester 9288 on. Start diagnosis (trigger).
Checking the K lead:
Same procedure as for L lead, but connect to socket 15 for K lead instead of socket 14 for L lead.
In case of the L lead, this signal must be displayed:
In case of the K lead, this signal must be displayed:
NOTE: If the displayed signals differ from the above, this may be due to interference caused by a control unit connected to the K and L leads (for diagnosable systems, refer to wiring diagram). Pull off control unit connectors one after another and repeat test of K and L leads. Start with alarm control unit, as described above. After the last control has been disconnected, one of the control units disconnected earlier must be reconnected since otherwise no signal will be present anymore.
If the airbag control unit is disconnected, control of the DME relay and, hence, of terminal 15 of the DME control unit is interrupted.
NOTE: The on-board computer (tachometer) Is connected to the K and L leads, but is not a diagnosable component. It may cause the above interference, though!
Disconnect alarm control unit and fit jumper
Disconnect connector 1 (black) from alarm control unit. Connect jumper to connector 1 of the alarm control unit, pin 4 and pin 6
Recheck signals of K and L leads, as described above
^ Disconnect other control units
Disconnect next control unit, turn ignition on, switch tester on and off and start diagnosis (trigger again).
Check signals of K and L leads.
Repeat process until all control units have been checked.
^ Check K and L leads for shorts to ground
^ Check each control unit for continuity to diagnosis socket