Micro Trainer CAN Basic
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A browser-based simulator that mirrors this board. Live CAN_H and CAN_L traces, the meter readings a multimeter would show, the bus topology, and all five faults. Flip a fault and watch the readings and the module status change together.

It runs on any device with a browser. There is also a download button on that page that saves the whole thing as a single file, so it keeps working on a classroom machine with no internet connection.

The complete tour of this board, start to finish. What a healthy CAN bus reads on a multimeter, where to place your leads, and then every fault mode one at a time.

Covered in order: what a CAN bus is, recessive and dominant states, what happens when two modules transmit at once, why a meter shows you an average, signal ground versus chassis ground, bus topology and the 60 ohm termination, and then each of the five faults with the measurements that identify it.

The full walkthrough runs long, so each fault also has its own short video that stands on its own. Work through them one at a time, or send students to the single one they need.

• CAN High shorted to CAN Low. Both lines read the same, around 2.45 V, with no difference between them. Watch
• CAN High shorted to ground. CAN High at 0 V, CAN Low pulled part way down to about 0.8 V. Watch
• CAN Low shorted to ground. The mirror image of the one above. Watch
• Open in the bus. Normal voltages at the DLC while modules past the break are offline. Watch
• Wrong termination. Voltages look fine, and 120 ohms instead of 60 with the key off. Watch

Bookmark this page rather than the individual videos. As more goes up, it lands here.

Everything you measure is printed on the back. The J1962 pin assignments, the voltages and resistances a healthy bus should read, and the diagnostic steps to follow. Students should not need a handout to use this board.

Battery. One CR2032. Switch MASTER off when you are done and a cell lasts a long time. When the LOW BAT light comes on, replace the cell before trusting a reading, because the measurements drift as the cell falls.

Voltage with the key on, resistance with the key off. Termination has to be measured with MASTER off. Measuring resistance on a live circuit gives a false reading, on this board and on a vehicle.

The status lights are for the trainer, not the vehicle. NO COMM and DEGRADED COMM tell you what a scan tool would find if you plugged one in. No vehicle has these lights.

Every board is tested and programmed before it ships. If one arrived damaged or fails in normal classroom use, email me and I will make it right.

Include your order number and a photo of the board if you can, which usually gets it sorted in one reply.

Email: scott@sbctrainingllc.com

Thank you for supporting a small shop. This board exists because students were being handed a scan tool before they understood what a multimeter could already tell them.

I build trainers and curriculum for other systems too, including lead acid batteries, relays, and series and parallel circuits. If your program needs something that does not exist yet, tell me what you are trying to teach and I will tell you honestly whether I can build it.