Basic Can Bus testing .......

[aesmith]

Hi,
Is anyone aware of a basic test I can carry out at the Canbus level? I want to see whether the fault lies with one of the vehicle controllers (ECU on rear "Haldex") or whether the vehicle is either not talking to it or not receiving it's response.

Essentially the vehicle tests all appear exactly as if the module wasn't there, in fact the results are exactly the same if it's disconnected. However I have tried a different ECU so the fault must either be something on the vehicle side stopping it communicating, or something in the assembly that causing the ECU to shut down.

Thanks, Tony S

 

[Kevy]

Hi Tony

Maybe post the question on an automotive forum or if it’s a car from VAG (who use the Haldex system) then get hold of VAGCOM which is a pretty good diagnostic tool

 

[aesmith]

Hi, thanks. It's a Freelander 2, I've been posting on a vehicle specific forum, just wondered if there was more specialist knowledge here. I have a "Foxwell" code reader that can read Land Rover specific codes, but I'm kind of stuck because it's seeing no response at all from the Haldex ECU. Exactly as if it weren't connected or even fitted. That's why I wanted to see if there's a way to test the Canbus connection itself, see if it's receiving messages from the rest of the vehicle.

 

[Kevy]

Is it a basic Foxwell which only reads the generic OBD2 codes or can it read specific manufacturer codes?

Get hold of (Mongoose) JLR SDD and a cable which will allow you access to full dealer level diagnostics and module programming etc. which may help substantially more...

 

[aesmith]

The code reader is Land Rover specific so can read their proprietary codes. I can access the various modules, all except the RDCM report error codes indicating lack of communication with the Haldex (U0136-00 or U0136-87). If I try and connect to the RDCM specifically it just fails to communicate, no error codes or firmware version etc. Just as if it wasn't there.#

With the Land Rover specific stuff you mention, would that plug directly into the Haldex ECU? It seems from my small experience that nothing can talk to it via the main diagnostic connector, so really I want to connect or test either in place of the suspect ECU so I can confirm wiring and bus is all OK, or connect to the suspect ECU to test it directly.