General Information

Engine Control
U0001 High Speed CAN Communication Bus off - General Information

Component Location





General Description

This vehicle has a Control Area Network CAN bus sytem. CAN is a methed of comunication between the PCM and other control units. Some of the other control units that could be on the CAN lines are PCM, TCM,ESP PCM, ABS and BCM. The CAN consist of a 2 wire network, a high and a low wire. A vehicle can have two CAN sytems. A High Speed CAN for engine, trans and ABS and a Low Speed CAN for BCM and windows.

DTC Description

Checking CAN communication, under detecting condition, if an error within the detecting condition is detected for more than 1.5 sec., PCM sets U0001.

DTC Detecting Condition





Diagnostic Circuit Diagram










Signal Waveform & Data




Fig.1) Can communication waveform at idle

Monitoring CAN HIGH and LOW simultaneously is important in monitoring CAN communication waveform. When CAN HIGH signal rise to 3.5V and LOW signal drops to 1.5V - voltage difference between HIGH and LOW signal is 2V - at BUS IDLE state(DIGITAL "1") whose reference voltage is 2.5V, "0" is recognized. Besides, comparing HIGH and LOW signal if opposite waveform is detected with the reference voltage of 2.5V, Check if current cam signal transfers correctly. Continuous "0"signal above 6BIT means the occurence of error in CAN communication. 1BIT is easily distinguished as calculating the time when "SOF"(START OF FRAME) which notifies the start of frame occurs. Check if "0"signal above 6BIT is detected continuously when monitoring CAN communication waveform.