CANbus Network Tester

This CANbus Network Tester (CNT) is specially designed to check the line resistance as well as the operating signal voltages of CAN High and CAN Low in a high-speed CANbus system in times of communication problems caused by poor wiring or incorrect terminations resistance.

This device assists Technicians in troubleshooting CANbus communication problems in High-Speed CAN circuits. It checks its operating circuit (line) resistance, CAN high and CAN Low signal voltages to determine whether it falls within the required operating parameters at normal conditions. During the test it will display the final results e.g., GOOD, Shorted, etc.

Its operation is simple and provides quick troubleshooting guide in diagnosing High Speed CAN Network problems. It also provides test points for oscilloscope connections to enable further investigation of the CAN signals waveform during engine problem diagnosis.

Exclusive Invention

1. CANbus Line Resistance (Ω OHM) check- to test circuit integrity.

In the CAN bus network, there are two terminating resistors of 120 Ohms connected parallelly at each end of the circuit (one at the ECU and the other at the BCM). The total resistance can be measured via the DLC (vehicle’s OBD2 connector).

The correct termination should read approximately 60 Ohms (two 120 Ohm resistors in parallel produce a resistance of 60 Ohms).

The tester covers all possible CAN pins combinations such as  [pin 1 & pin 9], [pin 3 & pin 11], [pin 6 & pin 14] and [pin 12 & pin 13].                                                                    

The results will display the terminal resistance of the circuit and also the final results for example GOOD, SHORTED, etc.

The Green LED in [RESULT] will light up to indicate [PASS] which means the measured terminal resistance is within the accepted Ohm W range.

2. Individual Pin Signal Voltages Check

This test is to check whether there is any signal voltage present in each of the 16 pins at the OBDII - Diagnostic Link Connector.

The green LED at VOLT CHECK in [TEST IN PROGRESS] will light up

CAN communication problems may result due to wrong voltage levels in the BUS is incorrect. Good CAN High range between more than 2.50 Vdc to less than 3.55 Vdc (Peak Volts).

3. Signal Voltages Check on CAN High (Pins 1, 3, 6 & 12).

CAN communication problems may result due to wrong voltage levels in the BUS is incorrect.

Normally the voltage should be between 2.0 V and 4.0 V. If it is lower than 2.0 V or higher than 4.0 V, it is possible that one or more nodes are faulty. For a voltage lower than 2.0 V please check continuity of CAN High & CAN Low lines. For a voltage higher than 4.0 V, please check for excessive voltage.

4. Signal Voltages Check on CAN Low pins (Pins 9, 11, 13 & 14)- good CAN Low voltages ranges between more than 1.50 Vdc to less than 2.55 Vdc (Peak Volts).

5. Voltage Check on Pins 4 & 5

Sample result of Pin 4 test

6. Voltages Check on Manufacturer Designated Pins (2, 7, 8, 10 & 15)

Unique Features / Application

1.       Oscilloscope test point connections - it comes with BNC to dual Banana plugs test lead -  use to connect to oscilloscope if further examinations of the CAN signal waveforms are required during engine troubleshooting diagnosis.

2. Ground cable with crocodile clip to be connected to a good vehicle ground.

3. Connects to Breakout Box that provide male OBDII output connector to add further diagnostic functions.

FUNCTION

Whenever there is CAN communication problem, the tester can perform the following tests:                                            

1. CAN circuit termination resistance check on pin combination such as Pin 6 &14, Pin 1 & 9, etc. with tests result remarks and recommendations after test.   

2. Individual Pin voltages test on all the OBD2 -16 pins such as CAN Low - Pin 14, CAN High - Pin 6, K-Line - Pin 7, L-Line- Pin 15, Chassis - Pin 4 or Digital Ground - Pin 5, Power input - Pin 16, etc. without having to probe with test probes.

Specification

        ·   Screen – (128 x 64 pixels) monochrome LCD Display

         ·   Ohms measurement range - 1,000 (1.0K) Ohms (max) 

         ·   Ohm Resolutions - 0.1 Ohm

         ·  Volts measurement range - 40 Vdc (max)

         ·  Volt Resolution - 0.01 Vdc

         ·  DC Volts Accuracy - ± 3% Reading

         ·  Working Temperature - 0ºC (32°F) ~ 50ºC (122ºF).

         ·  Power supply (Internal Batteries) - 6.0 VDC (1.5V x 4pcs AAA Dry Cells)