Multiplex Signals

This wave form image shows the body CAN from a Mercedes C180, which was suffering many operational problems, caused by a faulty window regulator. The first part of the image shows the signals with the regulator disconnected, followed by connection which corrupts the CAN.

Mercedes CAN signal fault

The wave form below is that of CAN multiplex on a 607(ISO 11898-2), as measured at the ESP ECU. This signal is a good signal, despite the 'kick' in amplitude.


The wave form below is a sample of the PSA VAN Body network, accessed at the drivers side window control unit on a 307. You'll notice the Blue wave is corrupted. This manifested itself in the form of strange messages appearing on the multi function screen and intermittent faults with operation of windows etc.

The following wave forms are that of the same vehicle as above, after a replacement BSI was fitted. The original BSI had been subjected to water ingress.

This wave form is a good sample of a CAN 500kb/s (ISO 11898-2), high speed network taken from a 407.

The following wave form is of the same CAN high speed network, but sampled as a differential. This means I have measured across the CAN High and Low with one channel. This shows the differential voltage that the ECU looks at.

This wave form is of the new CAN low speed network, (125 kb/s, ISO 11898-3), sampled from the same 407 as above. Note the differnt voltage range, which is the same as the VAN network.

CAN Multiplex signal, High and Low. Good signal.


Last Reviewed: 27 March 2016Copyright © 2004...2016 Mark Stammers