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CANBus – How to reset a crash

2 min read

Hopefully, if you’ve been following previous articles, you’re feeling a little more confident about interacting with the CANBus. However, there is a good chance that it isn’t going to go smoothly at some point connecting to the car! It’s almost inevitable that you will crash the CANBus and need to perform a reset.

Risk/Reward – Staying safe

You’ll need to assess the risk of turning your car into a paperweight Vs the reward and satisfaction of being able to listen to it. A CANBus crash on the Medium Speed CAN is very unlikely to stop the car from starting and driving, so I recommend starting here. It’s also easy enough to pull over and reset the CANBus, which has crashed.

User induced bus crash

The most likely error will be in your wiring between the CANBus adapter and the car, so be careful to pin out all of the connections on the lead you’ve made. Double-check the instructions that came with your adapter for the correct pinning. If you’ve got something wrong, and short out the CANBus, it will crash (the communication, not the car).

Next will be the configuration of the channels and their speeds in BusMaster. If you get this wrong and connect a high-speed adapter to a medium speed can, in theory, BusMaster will crash as it is only listening. There is a risk that the car’s CANBus will crash!

Don’t panic, it’s not as bad as you think!

Unhappy instrument cluster on a crashed CANBus
The unhappy instrument cluster on a crashed CANBus.

So what if the CANBus crashes? The dash will light up with a Christmas tree, the colour will drain from your face, your butt will clench, and a cold sweat will start to form. This happens to us all the first time. Don’t panic. It’s not as bad as you think!

Soft Reset – Disconnect and let it sleep

Stop BusMaster, disconnect the USB adapter from the PC, disconnect the OBD-II lead from the car. Turn off the ignition, get out of the car, lock the doors and go and get a brew. You’ll need to give it at least 5 minutes, but making a brew properly should take this long!

More than likely normal communication will resume, some trouble codes will be left behind in the car’s memory, but all the modules will carry on as if nothing happened.

Hard Reset for a CANBus Crash

A ‘soft’ CANBus crash reset won’t be enough in some circumstances, and you’ll need a hard reset. To do this, disconnect the battery negative terminal and give it 30 minutes. In this case, you’ll lose the clock setting and trip memory (including fuel consumption). But, it’s not the end of the world!

M

prev: CANBus Whispering
next: Interpreting Frames

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