Dear all,



Here I have a problem with my High and Low Speed CAN bus and this stop me from starting the car...

I really need help.

On the diagnostic socket (OBDII) on the yellow and black wire, PIN 14 (Low Speed CAN bus) the voltage is only 1.3V but on yellow and brown wire, PIN 6 (High Speed CAN bus) the voltage is ok at 2.5V.

I have read that if I have a problem on the BUS system (module not working properly) the voltage would be too high, around 7.0 V but I have not found anywhere the reason why the voltage could be too low....

At the same time when I remove the battery and check the Resistance, between the PIN 3 and 11 it's ok I have 60 Ohms but again between the PIN 6 and PIN 14 I have 120 Ohms, this result confirm that I have a problem...

Please, can someone guide me where to search the problem ?
If I'm wrond somewhere please tell me too !!!!

Thank you so much in advance


Down I attach what I have found about the CAN bus system, it's long but it can be helpful for someone else....

Discovery 3 OBD II connector, Pin 11 CAN Low, Pin 3 CAN High Or, Pin 14 CAN Low, Pin 6 CAN High
Yellow/Black CAN Low Yellow/Brown CAN High using a multi meter + to the pin - to earth the reading will be 2.5 Volts

If the voltages are excessive, for example CAN High is reading 7.0 Volts, then remove the suspect module by disconnecting it and see if the voltage returns to 2.5 Volts if it does then, the problem is solved
Obviously the voltage will fluctuate when reading


Two CAN busses are employed on the vehicle:

* Medium speed
* High speed

The medium speed bus connects the following control modules:

* Integrated Head Unit (IHU) or low line head unit
* Heating and ventilation control module
* Fuel burning heater
* Park distance control
* Tyre pressure monitoring control module
* Central junction box

The high speed bus connects the following control modules:

* Steering angle sensor
* Air suspension
* Electric park brake
* Electronic rear differential control module
* Terrain Response™
* Restraint control module
* Engine control module
* Transmission control module
* Adaptive front lighting system control module
* Antilock Braking System (ABS) control module


IDS Vehicle Integrity Test
Both the medium and high speed CAN bus are connected to the Instrument cluster and the diagnostic socket at one end. The Medium speed bus terminates at the Central Junction Box (CJB), while the high speed bus terminates at the ABS control module.

Control modules are connected in either a loop, CAN in/CAN out, or a spur configuration. Should a control module that is looped fail, that bus system will fail at that point. Should a spurred control module fail the rest of the bus system will be unaffected by the faulty control module.

If a control module is suspected of non-communication, the Network Integrity test application available on the manufacturer approved diagnostic system, can be used to confirm if communication is possible between the control modules on the vehicle and the manufacturer approved diagnostic system (via the J1962 diagnostic connector ). The results from the test can be used to determine if either a single module or multiple modules are failing to communicate.

CAN Terminating Modules

If the Network Integrity test indicates that one or more module on one of the CAN networks (HS or MS) are failing to communicate, there are several checks that can be made. The first step is to identify if both of the CAN terminating modules on each individual CAN Bus are communicating. If both CAN terminating modules for each individual CAN Bus are communicating (identified via the Network Integrity test), then it can be confirmed that the main 'backbone' of the CAN harness is complete. The main 'backbone' of the CAN harness consists of all the modules connected to the CAN harness via a 'loop' configuration and also includes the two terminating modules.

Communication with both CAN terminating modules via the Network Integrity test confirms the physical integrity of the main 'backbone' of the CAN harness (and the harness spur to the J1962 diagnostic connector). This means that there is no requirement to check the resistance of the CAN Network. This is because the standard check for 60 ohms across the CAN High and CAN Low lines will not provide any additional information regarding the physical condition of the CAN harness, beyond what has already been determined from the Network Integrity test.

Non-Communication of a Terminating Module

If a Network Integrity test reveals a terminating module is failing to communicate it can indicate a break in the main 'backbone' of the CAN harness. The first checks should always be to confirm the power and ground supplies to the non-communicating module are correct. Providing these are correct, the resistance between the CAN High and CAN Low lines at the J1962 connector can be checked to determine the integrity of the main 'backbone' of the CAN harness. After disconnecting the battery a reading of 120 ohms would indicate an open circuit in the main 'backbone' of the CAN harness. Alternatively, a reading of 60 ohms would indicate that there is no open circuit fault with the main 'backbone' of the CAN harness.

It is worth noting that even if one of the terminating modules is disconnected from the CAN harness, communications between the modules still connected may still be possible. Therefore communication between the manufacturer approved diagnostic system and the connected modules may also be possible.


Locating CAN Harness Open Circuits

In the case where multiple modules, including a terminating module, are failing to communicate, having first confirmed the power and ground supplies are correct, the approximate location of the open circuit can be identified from analysis of the Network Integrity test results and reference to the relevant CAN network circuit diagrams. For example, if an open circuit existed in a certain position on the CAN harness, any module positioned on the Network between the J1962 connector and the open circuit should return a response during the Network Integrity test. No responses would be returned from any modules past the open circuit fault in the Network.

CAN Harness 'Spur' Type Configuration Circuits

If, after the initial checks (Network Integrity test using the manufacturer approved diagnostic system, and power and ground supplies to the module have been checked and confirmed as correct), a module that is connected to the CAN harness via a 'spur' type configuration is suspected of not communicating, then the physical integrity of the CAN harness 'spur' can be checked.

This is most easily undertaken by individually checking the continuity of the CAN High and CAN Low lines between the non-communicating module connector (with the module disconnected) and the J1962 diagnostic connector.

'Lost Communications' DTCs

As well as the methods described so far in this document, which can be used to determine the location of an open circuit in the CAN harness, 'Lost Communications' DTCs can also be used for this purpose. Lost communication DTCs mean that a module is not receiving CAN information from another module.

For example, if a global DTC read were to be carried out, only DTCs stored in the modules that the manufacturer approved diagnostic system could communicate with would be displayed. If there was an open circuit fault in a certain position on the CAN harness, the modules that could display DTCs would all be prior to the open circuit on the Network, and these modules should display 'Lost Communications' DTCs with all the modules located on the Network past the open circuit fault.

 

Wiring diagram attached. You will see that many modules are connected to "talk" on this network line. Any partial short or defective module can drag down the voltage (despite the quoted comments about failure only impact to that leg), and keep others from talking. Pretty hard to troubleshoot with just a volt meter.

Other than a dead short, ohm readings of electronics modules (semiconductor junctions) will vary because of your meter design, the voltage it uses to sense ohms, etc. You can get varying readings based on polarity of your probes.

Another method is to use a diagnostic scanner that can talk to the various modules from the OBDII port, and see which ones are speaking up when called, and which are not responding.

Can be more than one.


Everything is so dependent on computers being awake and talking to each other, makes battery problems that much larger. Eventually you won't be able to do anything without a dealership computer connection.

Kinda like this sign from the computer room:

"Achtung!
Alle touristen und non-technischen lookenpeepers! Das machine is nicht fur fingerpoken und mittengrabben. Is easy schnappen der springenwerk, blowenfusen und poppencorken mit spitzen sparken. Das machine is diggen by experten only. Is nicht fur gerwerken by das dummkopfen. Das rubbernecken sightseeren keepen das cottenpicken hands in das pockets. Relaxen und watchen das blinkenlights."

 

Thank you so much Savannah Buzz,


I have also a MSV-2 to help me.

Maybe you remember, I can't talk with the car when the four flashers are on, at this time, my Water Gauge Temperature is also way in the red.
But when the gauge is going back to normal, the flashers are off I can talk with the car, even if the dashboard os like a Christmas tree.

I will show you some results...
......ten minutes later.....
No way to attach HTML files on this forum and the size max for a Word file 19.5kb.... alalalalalalalala.....

Also here the results:

Here are SOME example of the missing ECU Sometimes they are there sometimes not....

SM129 INSTRUMENT PACK

SM129 ENGINE MANAGEMENT
SM129 PARK BRAKE MODULE
SM129 STEERING ANGLE SENSOR MODULE

SM129 ABS CONTROL MODULE

SM129 TRANSMISSION CONTROL MODULE

About the faults they are plenty U faults....
But this one is coming always:

AIRBAG
-:B0095
and this one is coming sometimes...
AIRBAG
-:B00D2


I think I have to work with both.... the multimeter and the MSV-2
I have also checked today the Instrument cluster....
The Volatage was unstable when I was touching the plug at the Cluster...
But anyway I'm not sure that is the problem, I have seen some were changing the Instrument Cluster and still had the problem...

But what I have seen, when the flashers are one and the Water Temperature Gauge is up, the Voltage on the Yellow and black wire on the PIN 14 of the OBDII drop to less than 2.0Volts

Now why that happen, it's my question.... and it's not an easy question...
I would like to check the beginning of the CAN bus system to be sure that this one always receive the 2.5Volts... to be sure that the problem is not between the battery, or the Battery Junction Box or the Central Junction Box.
If the problem is not there I would be happy !!!!

My only concern is the problem is on and off and without any reason....

You can check on my other Thread to have a full detail of my problem.

Thank you in advance for your help !!!

 

Having 120 ohms on the HS CAN means that one of the terminating modules is not attached to the DLC. The most common issue with these is corrosion at the t-case ECU connector. This is one of the modules that is a pass through, and if not functioning, will not allow proper comms through the system.

 

Dave, what is the normal resistance reading if the end-of-line termination is present?

 

Each terminating module(IP & ABS for HS, IP & CJB for MS) has a 120 ohm wired between the high and low sides of the respective BUS, which when functioning normally will show ~60 ohms when tested from high to low sides at the DLC.

 

Roverguy7,


Thank you so much !!!
What is exactly the T-Case at the ECU connector and where is it ? What is the DLC ?
Sorry I'm not yet a Professional of Land Rover...

I have forgotten to tell you that I'm the guy living in Liberia, no Land Rover dealer here... except me if I start !!!

I have to do everything by my own.

Second question, how to know for sure when a module is dead ? Can we use a multimeter to know that ?
I ask the question because the problem is on and off... sometimes all the modules answer to the MSV-2, sometimes only one is missing and sometimes 6 are missing... and I can't change all of them...
Also is there a test to know for sure which module is out ?

About corrosion, I have already removed the seats and check the wires there, no corrosion at all for any ground wires and any wires... I have fixed some wires that were "nude".
I have checked also the two electronic boxes behind the battery (sorry I have forgotten their name...), both connection and boxes are really really ok, no corrosion at all...

But anyway we wnever know.

I'm really open to everyone, my car is stuck since February.... I really need help !!!!

Thank you so much in advance to everyone !!!

 

T-case ECU is one of the ones behind the battery, and likes to get corrosion in its connector.

DLC is the diagnostic connector that you're hooking up to.

You're going to need to check resistance across the can wires into both the ABS and the IP to make sure they're ok, should see 120 ohms on each. If good, you'll need to separate the HS CAN at its various connectors and ohm out from each to the IP and ABS connectors to see if you're open circuit at any point, and narrow it down from there.

 

Thank you so much for your answer,


I think it's ok with the T-Case ECU, like I told you I have checked it carefully and I spray it too with WD-40. Everything was really looking like a brand new one, no corrosion at all, no trace of water anywhere.

Where is the ABS box or module ? What is IP ? Sorry again for my so simple question... sorry... and thank you for your patience !!!

Can you please, please and please again tell me more in details how to check the resistance ?
I imagine I have to measure the resistance on the PIN of the module and not of the plug going to the module, is it correct ?

I'm so sorry to don't be able to understand right away your counsels.... I'm really not an electrician... I was working in chemistry...

Thank you again so much and don't forget I really need your help here in Liberia !!!!

PS: I'm not able to perform any measurement now... I have to find again another Multimeter... but I hope I will have one on Saturday....

 

Also finally it was the connection behind the instrument cluster.
I had to put something to make the connector attached to instrument cluster more stable.

It's working, so good.

Thank you to everyone !!!