Aerial diversity is a system that select the aerial with the best reception from the up to 4 aerials in the vehicle. This signal is amplified in the diversity and passed on to tuner. The following briefly describes the tests that can be run in the aerial diversity test module.
The DC measurement detects whether the diversity is correctly connected to the tuner. In the test module, the corresponding fault code memory entries are also evaluated.
The aerial self-diagnosis checks the diversity function and aerial connection. However, these results are not always meaningful. In this case, it is necessary to examine the field strength of the receiveable stations.
In the Service mode of the radio, there is the possibility to display the quality and field strength of the radio station currently being picked up (not M-ASK and CCC). The displayed values lie between 0 and 15.
Proceed as follows to call up the Service mode:
If the result of the diversity self-diagnosis is OK, the field strength of the currently received station can be displayed in the test module. If one aerial has a noticeably weaker reception than the other aerials, the vehicle must be turned by 90 degree and the measurement repeated. If there is still a violation of the tolerance range, at least one FM aerial is defective. The defective FM aerial must be checked.
In the diagnosis, the AM amplifier is inactive and therefore delivers level values with the AM amplifier switched off during an AM scan. To evaluate the AM aerial with the active amplifier, the test is concluded by switching the switching voltage from the diagnostic mode into FM1 / AM mode. With the amplifier switched on, the level values must be significantly higher than those with the amplifier switched off. If this is not the case, the Radio_on cable must be checked.