Hi,

Is anyone aware of a way to test the CAN Bus itself? What I want to do is connect "something" in place of the Haldex ECU (RDCM) and see whether it's receiving the correct signals when my tester or the other modules try to contact it.

Thanks, Tony S ----------
Tony S

I use a Picoscope for Can testing.
If I have a problem the Pico can freeze a frame, I then get it to carry out a mathematical equation which is actually the signal ( difference between high and low. Then the Pico can carry out a binary conversion to confirm whether the signal is corrupt.
Should I have a corrupt signal the binary figures appear in Red and the ACK has a red cross to confirm the signals not accepted
If the signal wire has a short or live feed to it is very obvious on the network via the scope reading.

This is a very accurate way of fault finding on Can networks but very few actually understand it or have the patience to see it through. Most just start swapping parts ! what i call guessnostics

Enjoy Jaguar x-type sport gone
Jaguar x-type 2.2d sport one of my best cars ever sadly gone
Freelander 2 GS auto 2008 most unreliable ever ! gladly gone
Freelander 2 GS manual 2013 only time will tell !

There are 2 CAN networks. As you are talking about Haldex, I suppose that you want to test the high speed (500kbs) CAN network.

For starters, you can statically test the network impedance. There are two 120 ohms terminating resistors, one on the CJB and one on the engine ECU.
With battery disconnected, put an ohmmeter between CANL and CANH and see if you get about 60 ohms.
Better to do this on the connector of the Haldex, as in this way you verify the wires to the Haldex too.

Then, you can connect a CAN sniffer on the Haldex connector and see if you'll get valid CAN messages.
All ECUs are broadcasting parameters/values on specific IDs and the ECUs that need them are listen on those IDs. The Haldex is no stranger of this method.

oldgeezer wrote:

I use a Picoscope for Can testing.

The high speed CAN, complies with ISO 11898-2.
Start familiarizing yourself with the CAN bus by reading the wiki page below.
And yes, all devices broadcast, unsolicited, their status and info on the bus. Who needs the info is using it, who doesn't needs it can filter it.

https://en.wikipedia.org/wiki/CAN_bus




 

Thanks Alex for link to CAN info. Can you get it stuck to top of 'Tech Section' as we have had many questions on fault finding of complex (CAN?) faults. FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 77k+ miles) (MY2015)
Metro in its 11th Year of (Extended) LR Warranty / Full LR Service History
(Expensive, but Trouble/Worry free - hopefully?)

Impedance measured at the connector (disconnected from ECU) comes out near enough correct, 61.8 ohms. Next steps I think are going to depend on what gear I can get hold of. If I can get a scope I can have a look for CAN waveforms at that point, showing that CAN data is available at the connector. It should be fair to assume that if the bus is sending data to the connector, then the wiring is correct and would be able to pass data back the other way. If nothing's visible at the connector then something's wrong with the CAN Bus upstream. ----------
Tony S

Surely unless you can record and understand what is being said on the CAN bus you are wasting your time.
In my experience fault finding on the lower physical levels of a network only follows after understanding a fault is not caused by incorrect/failing signalling from an ECU or sensor.

Even then, (if it is the physical layer) the problem may be seen by closer inspection of wiring runs and checking connectors and their pins/contacts.

I have not been in the computing trade for some 20 years, but I would be very surprised if automobile electronics do not contain some self diagnostics, and respond to off-line tests by the correct diagnostic equipment.

Please can someone with knowledge of present day testing of cars tell us what is or isn't possible to the home mechanic.

PS I looked up FL2 diagnostics and found this
https://blackbox-solutions.com/help/SM132.html FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 77k+ miles) (MY2015)
Metro in its 11th Year of (Extended) LR Warranty / Full LR Service History
(Expensive, but Trouble/Worry free - hopefully?)

Quote:

Surely unless you can record and understand what is being said on the CAN bus you are wasting your time.

Tony
I have looked back through your postings since you joined the forum and, from what I read, I am still of the opinion that your fault is elsewhere and your suspect ECU is not faulty in itself but is being sent duff gen.

Below are two abstracts from the Repair Manual, are you sure that the self test is not reacting to that duff gen from somewhere else.

Control Module - Generation 3 and 4 Couplings
The control module, attached to the casing of the active on-demand coupling, forms a single unit with the control valve/axial solenoid. By analyzing information from other vehicle modules and sensors the control module regulates the axial solenoid to control the hydraulic fluid pressure supplied to the clutch plates. Some of the modules and sensors the control module communicates with are listed below:
Hardwired: - Control valve / axial solenoid - Electric hydraulic pump - Oil pressure and temperature sensor High speed CAN (controller area network): - Engine control module - Anti-lock brake system / traction control module - Traction response switch - Yaw rate sensor - Steering wheel rotation sensor

The control module has an integrated diagnostics system, which constantly monitors the active on-demand coupling system as well as its input and output signals. If the control module detects a fault a Diagnostic Trouble Code (DTC) is stored. The DTC is accessed using the Land Rover approved diagnostic system.

Ian FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 77k+ miles) (MY2015)
Metro in its 11th Year of (Extended) LR Warranty / Full LR Service History
(Expensive, but Trouble/Worry free - hopefully?)

Quote:

...The control module has an integrated diagnostics system, which constantly monitors the active on-demand coupling system as well as its input and output signals. If the control module detects a fault a Diagnostic Trouble Code (DTC) is stored. The DTC is accessed using the Land Rover approved diagnostic system.

Sorry Tony, I missed reading your initial topic fully.

http://www.freel2.com/forum/post351911.html#351911

https://www.obd-codes.com/u0136

You have proved that the most likely fault is in the wiring, connector, or earths at (or near the Rear Differential). And you have ruled out the ECU. Therefore careful inspection and cleaning should identify problem.
Did you check continuity, resistance, power, etc at the Haldex connector?

Good luck, you must be almost there.
Ian

PS Have you checked power, I think its FB6 in Aux Power Box 15amp white blue wire feed. FL2 XS SD4 Auto 2010 2012-2017 (21k - 91k miles) (MY2011)
FL2 Metropolis SD4 Auto 2014 2017- (16k - 77k+ miles) (MY2015)
Metro in its 11th Year of (Extended) LR Warranty / Full LR Service History
(Expensive, but Trouble/Worry free - hopefully?)

Thanks. I actually thought of one more test I can make, other than the CAN Bus functional check. I checked for power and ground using a digital multimeter, so those were high impedance checks passing virtually no current. So as well as yet another check for physical cable or connector damage I think I'll rig up a pair of leads with an indicator bulb or similar. Check that the supply and ground can pass a couple of amps, and I can check for voltage drop on supply or rise on ground.

I would still like to be able to check the CAN Bus. As vehicles get more and more of these wretched electronics we need to be able to look at this stuff ourselves. ----------
Tony S

Just a thought: connect the tester - its CANL and CANH, with the help of some wiring adaption - on the Haldex connector.
If you can read all other modules on the high speed CAN bus, then the wiring is OK and all problems are on the Haldex electronics.

For my sins I am required to play CAN-Open at work.
I use a device from a company called HMI, it is sold as an IXXAT USB-to-CAN V2.

It does read and display can frames




https://www.freel2.com/gallery/albums/user...s_data.jpg Tangiers Orange - gone, missing her
Replaced by Ewok what a mistake - now a happy Disco Sport owner