(1) Normal waveform
(2) Open in both of the lines (CANH and CANL) of a CAN branch
Waveforms (waveforms shown using dotted lines) are not present
from an ECU or sensor connected to a CAN branch with an open
circuit in both lines. (Waveforms from other ECUs or sensors are
Because this waveform is similar to a normal waveform, instead
of using the waveform, the malfunctioning part can be narrowed
down by performing a CAN bus check.
(3) Short between the CAN bus lines (CANH and CANL)
If the malfunction is in an ECU, disconnecting the ECU will change
the waveform. If the waveform does not change, a malfunction in
the wire harness is suspected.
(b) CAN bus waveforms (reference) (Group 2)
The following CAN bus waveforms can be used only as reference. The actual measured waveform may differ
significantly depending on the location of the open or short circuit.
(1) Open in a CAN branch line (CANH)
An abnormal waveform is output from an ECU with an open in one
of its CAN branch lines. Because this abnormal output interferes
with the signals from other ECUs, the output of other ECUs will
also appear abnormal.
Narrow down the malfunctioning part by checking DTCs or
performing a CAN bus check, or by checking waveform changes
when ECUs or sensors are disconnected. The waveform will
change to one for an open in both sides of a CAN branch when
the ECU or sensor with an open CAN branch line is disconnected.