2013 BMW X3 N20 LIN BUS Fault code
New user, first post, TIA.
Having LIN BUS code and inspected the wiring harness but did not find any issues. Did not do an exhaustive inspection yet due to the complication of removing the plastic wire junction that mounts to the engine. We verified the integrity of the wires from the coolant pump to this junction.
There are two anomalies that I have observed in the LIN BUS waveform.
A) The single waveform - the strange behavior on some of the pull downs
B) The green and orange waveform - The green waveform is backprobed into the pump connector at the pump. The orange waveform is backprobed into the same wire but on the DME connector.
We also have a backprobe in the alternator LIN BUS and it is identical to the green waveform.
What I take away from this is we have EMF induced between the pump and the DME or the DME LIN BUS circuit is bad on the coolant pump channel. I'm not sure the latter checks out but without being an EE that specializes on automotive ecu's or a schematic of the DME, it's really hard for ‘ME’, to speculate.
I am thinking about trying to de-pin the LIN BUS pump wire on the DME and see if we have any EMF on it.
This vehicle came from a customer that had it to the local BMW dealer and they replaced the Coolant Pump. So I doubt the pump itself is causing the issue.
Ch 1 seems to be going below 0v. Where is your ground on that channel? are you set for AC or DC coupling? This looks to be a scope connection error.
I re probed and led everything and all signals are overlapped. So the issue seems to be the strange ‘packets'? That aren't pulled down properly. Thoughts? Is it better to edit everything here and remove the faulty waveform due to ground issue? Does that provide focus on the problem going forward or just make things more confusing? Thanks Chris
2V, though not perfect, is still acceptable for LIN bus LOW signal. Does the pump module have good powers and grounds (checked by loading)? diag.net/file/f131epxh5…
The single waveform’s strange sections are not pulling down as far the left side. Looks like 1.5v above ground. The green trace is swinging 12 volts. The orange trace is swinging about 12mv( a loss factor of 1000). That’s not possible on a good wire.
This is a known good LIN capture from a 2014 328i N20 back probed at the coolant pump (if I remember correctly). Maybe try wiggling - pulling on the harness while watching the scope in real time, and seeing if the pattern changes.
My next step would be to put the lab scope on the pump ground , looks like brown wire on the pump 4 wire connector. And watch the signal when the pump is running, make sure you use battery negative for scope ground.
Rod, same waveforms whether we ground probe at chassis negative jump terminal or battery negative. It appears the lin bus signal is cross talking somehow to the pump ground. That waveform is the same whether the pump connector is plugged in to the pump or not. Seems its not the pump itself interfering. We front and back probed the ground on the pump wire and chassis ground and its 6 ohms…
Well, we found a corroded eyelit ground for the pump ground on the block. We removed the oxidation and put a star washer in to help with electrical conduction. We still have the strange waveform where it's not pulling down completely on some ‘packets?'. While probed at the alternator lin bus at the alternator and pump lin bus at the dme, this abnormal waveform goes away when we unplug the…
the scopes I use have a filter option in the menu, I do not have a pico
If the rest of the users on this network bus are operating normally, the physical wire at the DME should be fine shouldn’t it? Or otherwise the other bus users would have a problem. Check to see if the oil level sensor data is working, the intelligent battery sensor is working, the alternator control is working. If all this is, then I would think the LIN bus is ok everywhere except, potentially…
After finding the bad ground to the pump. I am wondering if this pump didn't go from that. If we unplug the pump from the lin bus the signal shapes up to normal.
Curious…..as my wife has a 2013 X3 with the N20. I would spend some time verifying that it is in fact a new BMW pump and the correct pump. It's is a pretty expensive pump and there are plenty of Chinese knock offs out there. Even used pumps can sell for a couple of hundred dollars. Wouldn't be the first time the customer has offered incorrect details. There is also a simple procedure to put…
Thanks Logan!!! The dealership had it before us and replaced the pump with a genuine pump. I appreciate the heads up on the bleeding! Fortunately we are a Euro shop and have the same equipment the dealerships have, so all good there. 😅 There is a 200w and a 400w pump though and I havent got down that track yet. I would “assume” dealer would have used vin in etka online and got the correct…