Strange DAF LF can bus problem

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Strange DAF LF can bus problem

Post by ross_c »

Lorry was bought as a non runner, owner had then done quite a bit of welding and trying to boost start it quite a few times before taking it to anyone.
Took it to mechanic who could get no communication with anything, who replaced all ecu's with supposedly good ecu's assuming they were all blown but to no joy.

So now it has come to me, I jumped in and immediately seen milage not displaying on the dash, I seen this problem before...
Lifted up the drivers floor mat and sure enough a corroded can splice between diagnostic socket, tachograph and the rest of the network. And one burnt can wire from welding.
Repaired these wires and it fired up straight away. But no throttle.
With diagnostics I have communication
with everything inside the network, but not the two nodes on either end (tachograph and engine ecu). Both of which has 120ohm and there is 60ohms on the network.
All waveforms look good, stable and no interference.
I even created a mini network on each terminating node to see if I could connect directly to rule out anything on the rest of the network but couldn't connect to either of them.
Strange considering the milage is displaying, so the tacho is communicating with the dash. And no tacho / engine communication faults on any of the other ecu's.
I have all the original ecu's so swapped everything back on but nothing changed.

At a bit of a loss with this one if anyone can come up with any ideas?

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Re: Strange DAF LF can bus problem

Post by vasek »

Possible that only the exchange of information between the POWERTRAIN ECU takes place on this truck via the V-CAN.
And EDC diagnostics is carried out via the K-LINE bus ,or D-CAN.
Is there a VIC-3 module (or a previous generation module) in the configuration of this truck?
If this module is present, then - it performs the GATE-WAY function.
Then - you should check all communications on this ECU:

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Re: Strange DAF LF can bus problem

Post by Iver »

Would it not be easier to now establish that all Modules are on the network and communicating, Solve the non communicating issues if any then I would be inclined to work through Fault Codes and Live data.

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Re: Strange DAF LF can bus problem

Post by ben.martins »


And apologies for the late reply on this.

As mentioned being able to ensure which ECU's are online is going to be key here. I would be making use of the J1939 decoder and use the source address list to determine which ECU's are on which network. This is assuming you have an automotive PicoScope of course!

If you do, then I would be looking at going to the VIC-3 (if fitted) as by the looks of things you have all the networks present at this gateway. If all the ECU's are correctly connected then they should all be present, especially the ones that are needed to start the vehicle.

In any case, considering it doesn't start I would expect you have a long list of fault codes. If possible add them here along with the PSDATA files from the networks - in particular from V-CAN as we will be able to see if the powertrain ECU is present.

Please keep us updated and we will assist where we can.

Kind regards


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Re: Strange DAF LF can bus problem

Post by Sharpy »

It maybe a little to late reply to be of any help, I had a similar issue a few years back with an LF that had suffered a voltage spike from a nearby lightening strike which begun as a no start/no comms which was traced to a burnt wire but then like you started but no throttle, I cannot remember the diag process/symptoms that went with the fault in between but I remember the fix was a reflash of the engine ecu with a Davie.

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