Ring Break Test
WARNING: This page does not describe the selected car, but rather 59 other vehicles, including the 2009 BMW M5, 2009 BMW 650i, 2009 BMW 550i, 2008 BMW M5, and 2008 BMW 760Li. However, it is still accessible from the selected car via links, so may be relevant.
If there is a break in the ring (a defect between two control modules) the following fault patterns may occur:
- Transmit diode of the transmitting control module defective
- Power supply of the transmitting control module defective
- Internal control module fault of the transmitting control module
- Receiver diode of the receiving control module defective
- Power supply of the receiving control module defective
- Internal control module fault of the receiving control module
- Optical wave guide between transmitting and receiving control module defective
These faults may occur alone or in combination. To diagnose a ring break, the first step is to locate the two control modules between which the transmission failure has occurred.
This is accomplished with the ring break diagnostic function. Once the two control modules have been identified and the diagnostics have been performed, remember to check the power supply and ground circuit of both modules before condemning a module.
Testing of the transmit/receive diodes will be possible using the OPPS tester.