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Removing a CAN Bus Module

CANBus Communications Decoded

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Discussion and questions related to the course CAN Bus Communications Decoded

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I need to remove an ABS and EPS (electronic power steering) module, but I get a manfucature code which is strangley prevents the ECU from running some of the emission readiness tests. Is there a way or a product out there that could trick the ECU into thinking that these two modules are still plugged in and functioning?

G'day Jon. Most can-analyzer tools will let you create and send messages on the bus. Many of them support replaying logs of can messages they have previously recorded.

Ideally, you'd need to spend a bunch of time reverse engineering the data the ABS and EPS modules output, and get some device to generate the correct data, but... A slightly dirty hack that often works is to record the CAN data frames those devices output on a standard car, and then have an analyzer tool in your car simply play that recording back.

However, strong safety caution here, as you're dealing with ABS and EPS systems, it could be possible to get some really really strange results. Have the ABS pump / valve block, and powersteering system been physically removed from the car?

Hi Zac,

This is very helpful. A little background on what I'm doing is a 2011 Civic Si engine swap into a 2011 Lotus Elise for a customer. We do these K swaps often, but the challenge with this one is that he wants to make it smog legal. This means all of the emissions related parts need to be functioning and no check engine light. The Lotus does not have ABS or EPS, so we should be ok. Do you have any recommendations on what I can use to record the CAN data frames and play that back to the ECU? From a quick search, it sounds like I can use something like the Arduino?

Yes, it could be done with an Arduino based setup, and a shield on top to give the CAN interface hardware. You'd need someone skilled up with Arduinos and embedded development.

For recording the data, the KVaser Leaf Light and CANKing is probably where you want to be :-). If you have a read through this post: https://www.hpacademy.com/forum/canbus-communications-decoded/show/interface-and-debugging-tools there are a few good options in there.

Thanks, it looks like I need to do some more homework. I've been able to read the CAN messages with my Arduino set up. Now it's just a matter of sorting them out and figuring out how to get the Arduino to broadcast the right messages into the bus.

I've been able to capture and record the data while tapped into the EPS module. I'm hoping I can just play this back into the car. Does anyone know of a good way to do that? I'm open to using devices other than the Arduino if it makes it easier.

Also, I read the CAN messages coming from the EPS module on the bench and saw a single ID with 3 bytes. The first two bytes were 00 and the 3rd was switching between 5 different values. Is this typical? Would this single message be enough to trick the ECU into thinking that the module is still plugged in?

The only way to know if that will work is to give it a go, certainly worth trying! If you've got some Arduino experience, programming one to play back some CAN messages shouldn't be too tricky, or the devices mentioned above will do the job aswell.

I've been able to transmit a few messages into the bus, but without success. Any tips on how to find right messages to transmit? Is it possible that the engine ECU is constantly asking for a status request and expecting a reply from the EPS module? Meaning it would need to be timed or triggered by a particular message?

I've also verified that the EPS does not contain the terminating resistor

my educated guess is the messages either are 1)expected within a specific time period or in a specific sequence

2) contain a crc, checksum, and/or incremental value within the message as well.


Thanks, I'm starting to think the same. Any suggestions on how I can replicate that? I guess worst case scenario, I transfer all of the modules over and keep them powered up.

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