Cannot connect to gateway node of CAN bus through OBD2 port

Cannot connect to gateway node of CAN bus through OBD2 port
  • 4763
  • Christopher Thornton
  1. CAN bus and OBD2?
  2. CAN bus communication problems?
  3. What is a CAN bus error?
  4. CAN Bus connections?
  5. What is the difference between OBD and OBD2?
  6. How do CAN bus system work?
  7. How do you diagnose a CAN bus?
  8. Can you repair CAN bus wiring?
  9. Can error frame example?
  10. What is bus off error passive?
  11. CAN controller is in error passive state?

CAN bus and OBD2?

Link between OBD2 and CAN bus

On board diagnostics, OBD2, is a 'higher layer protocol' (think of it as a language) while CAN bus is a method for communication (like a telephone). In particular, the OBD2 standard specifies the OBD2 connector, incl. a set of five protocols that it can run on.

CAN bus communication problems?

CANBUS is a high speed network which requires high quality wiring in order to operate properly. As such, it is sensitive to improper wiring. The majority of CANBUS communication problems are caused by poor wiring, incorrect termination, or the use of multiple frequencies on the same bus.

What is a CAN bus error?

Types of CAN Bus Errors

A CAN bit error occurs when the monitored value is different than the value being sent. For instance, if a node is transmitting dominant (0) to the bus and recessive (1) is detected, this will cause a bit error. A bit error can also be detected by stuffing.

CAN Bus connections?

CAN bus uses two dedicated wires for communication. The wires are called CAN high and CAN low. When the CAN bus is in idle mode, both lines carry 2.5V. When data bits are being transmitted, the CAN high line goes to 3.75V and the CAN low drops to 1.25V, thereby generating a 2.5V differential between the lines.

What is the difference between OBD and OBD2?

In like manner, OBD2 is an advanced technology improved from OBD1. Thus, OBD2 provide better and more standardized vehicle protocols and system checks data. OBD1 needs corded connection while OBD2 can be connected hands freely via Bluetooth or wifi.

How do CAN bus system work?

How Does It Work? The CAN bus system consists of a primary controller that keeps watch over all vehicle systems from a central location. This makes it easier to monitor for faults, and then diagnose specific problems, rather than having to manually query numerous sub-controllers distributed throughout a car or truck.

How do you diagnose a CAN bus?

One step is to check the CAN bus with an oscilloscope. An overall bus check can be done via the OBD connector that is, in most cars, somewhere around the base of the steering wheel. Some imported cars will have the OBD connector in a similar area on the passenger side.

Can you repair CAN bus wiring?

Repairs to CAN bus wiring can be carried out either with sections of repair wiring with the correct cross section or with entwined wires “green/yellow” or “white/yellow” from the electronic parts catalogue (ETKA) → Electronic parts catalogue (ETKA). When repairs are performed, both bus wires must have the same length.

Can error frame example?

Figure 3 shows an example of an active error frame. An error frame is divided into two parts. ... Bit error • Form error • Stuff error • CRC error • Acknowledge error The bit error can only be detected by a sending node. Each node reads back the actual transmitted bit.

What is bus off error passive?

When any Error Counter raises over a certain value, the node will first become “error passive”, that is, it will not actively destroy the bus traffic when it detects an error, and then “bus off”, which means that the node doesn't participate in the bus traffic at all.

CAN controller is in error passive state?

CAN controllers in the Error Passive state can only indicate a detected error by sending six homogeneous recessive bits. This prevents the error-detecting receivers from globalizing detected errors.

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