Description of On-Board Diagnostic System
Notes on the BMW DIAGNOSTIC SYSTEM:
The LKM has diagnostic capabilities and differs as regard function depending on the country variant can be read out via the BMW diagnostic system.
The LKM has no direct diagnostic links (RxD/TxD) to the diagnostic socket of the vehicle. This link is made via the bus and the EKM.
Status monitoring:
The status of LKM switch inputs, relay control outputs and lamp power circuits can be monitored with the aid of *D* status monitoring. In order to combine status monitoring, as required, the individually selected inquiries can be indicated in a *D* status list.
The indicated status corresponds to the condition as seen by the LKM. A defect can be localized faster by comparing the display in the BMW diagnostic system with the status in the vehicle.
Component activation:
By way of component activation with *D* activate components, individual components can be driven separated from their logic operations.
It is possible to localize a defect faster by reading out the status at the input *D* status monitoring and activating the coresponding output.
When a function or a component is activated, the functions fog light, high beam and headlight flasher can no longer be operated from the vehicle. For this purpose, the screen page *D* activate components must be exited with *^*
The function "low beam switch ON" can only be performed with *D* activate components when the low beam light is switched off.
The reason for this is in the internal logic operation, in which the relay can be activated by the switch and by the LKM electronics.
Troubleshooting:
Notes:
General:
- Observe all safety codes and accident prevention regulations when performing all tests and work on the system.
- Battery charged, U-min = 12 V
- Wherever possible, the battery must not be disconnected otherwise the defects stored in all control units will be cleared.
- Perform wire checks only with control unit or component connectors disconnected
Caution!
Before monitored components are disconnected from the wire harness,
- deactivate LKM control unit
When the LKM is disconnected from the wire harness,
- deactivate LKM control unit
- check that pop-up headlights can move freely (danger of accident or damage to mechanics) or
- disconnect pop-up headlights and clear any stored defect codes after reconnection
Deactivating control unit:
The LKM switches off under the following conditions:
- Ignition switch in position "0", ignition key removed in USA version
- and the driver's door closed for 2 minutes or the closed driver's door opened and closed once.
Test equipment:
The adapters recommended for troubleshooting are listed in the chapter - Pin assignments.
Only use suitable test leads, terminals and test probes.
Defect Code Memory:
The LKM stores defect codes (see scope of monitoring) which occur in the lighting system during vehicle operation. The defects are signaled to the driver by way of the MID.
The defect code counter is incremented in the case of defects which the LKM has already stored and are signaled once again.
When storing the defect codes, the LKM differentiates between defects relating to lamps, fuses, relays and pop-up headlights. A corresponding message is displayed in the MID when the LKM detects a defect.
If the detected defect is a lamp defect which no longer applies before the LKM switches off (loose contact), then this lamp defect is not stored in the defect code memory. However, if the lamp defect is present before the LKM switches off, then this lamp defect is stored.
If a defect concerning the fuses, relays or pop-up headlights is detected, the defect code is stored in the defect code memory when the LKM switches off. Whether this is a current defect or not is irrelevant in this case.
The stored defect codes are not cleared by interrupting the voltage supply. These defects can be cleared and displayed via the BMW diagnostic system. The LKM defect code memory is updated when the LKM switches off.
*D* Status monitoring and *D* activate components can also be used for troubleshooting.