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Problem voltage BUS can system
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Phifross
 


Member Since: 02 Feb 2013
Location: Monrovia
Posts: 31

Nigeria 2005 Discovery 3 4.4 V8 HSE Lux Auto Java BlackDiscovery 3
Problem voltage BUS can system

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 Responseâ„¢
* 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.
  
Post #116175723rd Sep 2013 10:58 am
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Phifross
 


Member Since: 02 Feb 2013
Location: Monrovia
Posts: 31

Nigeria 2005 Discovery 3 4.4 V8 HSE Lux Auto Java BlackDiscovery 3
Follow up of the day....

After touching the Instrument cluster, it seems that something is happening there....

When I move a little the connection attached to the Instrument cluster, the voltage on the PIN 14 of the OBDII (Yellow and Black wire) is changing...sometimes 1.1 Volts, sometimes 2.3 Volts...
At last, it was ok with 2.3 Volts.
After that I disconnected the battery and I was so surprise to measure 60 Ohms between the PIN 6 and the PIN 14...
I don't think the problem is solved but it appears and disappear... that's a little bit frustrating because I have no idea why or what can cause it ?

What I would like is to check is if my Instrument cluster receive well the 2.5Volts...
Someone knows what is the PIN N° for the yellow and black wire and also for the Yellow and brown wire ?
Because the plug don't let us see where they are connected...

Here it is what was written about the High Speed CAN bus:

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.


Now I have some question about that:
What is a spur connection ?
It seems that the Instrument Cluster is not a CAN in/CAN out, am I correct ?
Does it mean that the instrument Cluster is the beginning of the CAN bus connection? Both High and medium?


I have seen some people have changed their Intrument Cluster for nothing, the problem was still there after changing the Cluster...


Now if my cluster receive well the 2.5V it means the problem is somwhere in the CAN Bus... if my Instrument Cluster doesn't receive the 2.5V it means that the problem is between the battery and the instrument Cluster... is it right ?

I really need help, I'm not an electrician... I'm a teacher and previously I was working in Chemistry...

I'm so so grateful for any help.

Thank you so much in advance !!!
  
Post #116200423rd Sep 2013 7:06 pm
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parrafin23
 


Member Since: 04 Dec 2011
Location: Buskeud
Posts: 678

Norway 2005 Discovery 3 TDV6 Commercial Auto Java BlackDiscovery 3

Its a good idea to post this here.
So you say you moved the wires goin to the ipac. wel this has one of the end resistors 120ohms. so what do you get if you measure the ipac's canbus? check the ohm value on the connector that goes to the ipac.

check pin 2 on connector C0230. this is hs can-l on the wiring diagram

Have you checked the integrated transfercase module? checked the values there?

but it looks like you have an issue with the ipac or the connector. I think there was someone here that had a fault in the wiring goin to the ipac. use the MM on the canbus wiring to and from the ipac and see what your reading are without the battery connected.

P.
  
Post #116238524th Sep 2013 3:10 pm
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rockcrawler
 


Member Since: 31 Oct 2012
Location: Ferring
Posts: 2884

United Kingdom 2006 Discovery 3 TDV6 Metropolis LE Auto Bonatti GreyDiscovery 3

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I'm off for a doughnut
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Post #116238824th Sep 2013 3:15 pm
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Phifross
 


Member Since: 02 Feb 2013
Location: Monrovia
Posts: 31

Nigeria 2005 Discovery 3 4.4 V8 HSE Lux Auto Java BlackDiscovery 3
Some translation needed...

Oh Parrafin23 you are here too ?


So good, happy to find friends !!!
Did you received my email to you some two weeks ago ? I hope so...

I'm so so sorry, I need translation about your post....

What is ipac ?
How to check the Ohm going there to the ipac ? It means where I do that... how to measure it I know Wink

Where is connector C0230 ? What is hs can-I? Are you talking about the wiring diagram you send me ?

What is MM ?

So sorry to bother you with stupid question... I'm really not an electrician.... but when someone explain me very slowly, I understand quickly Mr. Green

Thank you again so much !!!
  
Post #116259224th Sep 2013 9:04 pm
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Oswiperus
D3 Decade 


Member Since: 02 Apr 2010
Location: Chelmsford, Essex
Posts: 1590

United Kingdom 2005 Discovery 3 TDV6 SE Auto Java BlackDiscovery 3

iPac = Instrument cluster.
hs can = high speed can bus.
I have no idea what MM means!

Stu.
  
Post #116260324th Sep 2013 9:24 pm
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blue200tdi
 


Member Since: 23 Sep 2012
Location: Lincoln
Posts: 1094

England 2006 Discovery 3 TDV6 HSE Auto Java BlackDiscovery 3

MM = Multi-meter Very Happy
 You guys are gonna be busier than a test bench in a plunger factory!
Java black 2006 2.7 TDV6 HSE AUTO.
2014 Kawasaki ZZR1400 Performance sport. 
 
Post #116261924th Sep 2013 9:45 pm
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Phifross
 


Member Since: 02 Feb 2013
Location: Monrovia
Posts: 31

Nigeria 2005 Discovery 3 4.4 V8 HSE Lux Auto Java BlackDiscovery 3
Ohm measurement result on C0230

Thank you to everyone for the translation.

Also under the heavy liberian rain I was able just one measurement.

With my MM Laughing I have measured on the CO230 between PIN 1 and PIN 2 120 Ohm
Am I correct to measure between PIN 1 (Positive HS CAN bus) and PIN 2 (Negative HS CAN bus)
I measured also 120 Ohm between PIN 17 and 18 (Medium CAN bus)...

Also the result of 120 Ohm, what does it mean ?

At the same time I checked also on the OBDII and same 120 Ohm between PIN 6 and 14 and also between PIN 3 and 11

No way to connect the battery to check the Voltage, rain too heavy here and so dark too...

I will keep you updated tomorrow !!!

Good night to all and thank you again !!!
  
Post #116264624th Sep 2013 11:09 pm
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Cellerdweller
 


Member Since: 05 Oct 2012
Location: Macclesfield
Posts: 1315

England 

Phifross

I'm not questioning your ability but do make sure that you are testing the correct wires it is easy to be caught out
The canbus will have two 120 ohm resistors at each end connected in parallel , if the circuit is complete , not broken then you should have a measurement of 60 ohms on the circuit . If it is broken then you will see 120 ohms .
The can bus also Carry's voltage , 2.5 v with the can idle and around 3.75v on can+ (high) and 1.25v on can -(low) when data is being transmitted .
You can view the can with a oscilloscope if you connect between can+ and can- .
A diagnostic tool connected to the 16 pin data link connector may help by showing you a control unit with a no communication fault . I would suggest if this is the case you check the module supply voltage and fuses and also check the earth .
Hope that helps a little Thumbs Up
 You're not afraid of the dark are you ?  
Post #116271025th Sep 2013 8:15 am
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parrafin23
 


Member Since: 04 Dec 2011
Location: Buskeud
Posts: 678

Norway 2005 Discovery 3 TDV6 Commercial Auto Java BlackDiscovery 3

Heya Phifross. Ofc Im here too. Where else would i go to get some expert help?

When you used your MM and got 120ohms,was this on the ipac pins? the pins that the connector fits? As Cellerdweller says there is 2 120ohms resistors connected @ each end in the canbus system in parallel. So the current from your mm is split 50-50 over these resistors. so the mm will show 60ohm when the canbus is ok.


Yes I did recieve you email. been a hard and akward week for me, im not in tip top shape to do mutch. The doctors "thinks" that i got a nasty heart condition that needs takin care of, but they are not sure how to tackle this yet. All they say is " I think its this and i think its that, or perhaps its more like this than that" and so on.. I just closed my eyes and put on some Metallica and listen to the track "the day that never comes"

But ill be here to the end of me.

P.
  
Post #116300925th Sep 2013 4:57 pm
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Phifross
 


Member Since: 02 Feb 2013
Location: Monrovia
Posts: 31

Nigeria 2005 Discovery 3 4.4 V8 HSE Lux Auto Java BlackDiscovery 3

Dear Cellerdweller,


No problem at all and you can even question my ability, because my ability is not good about elctricity !!! Really don't worry and feel free to tell me I'm wrong and to give detailed advice.

I was sure to measure the resistance between the PIN 1 and PIN of the C0230, it means the plug going to the Instrument Cluster.

Now that's true I didn't check on the PIN of the Instrument cluster.... but I think I will not measure anything simply on the PIN of the instrument Cluster isn't it ? The goal was to measure the CAN bus ressitance, no ? Please give me a confirmation...

About the resistance of the OBD II, yes I'm sure about it, I checked the color of the wires and only sometimes I have a resistance of 60Ohms, I know I have a problem somewhere in the CAN bus... my only problem is to locate the problem...

Mmmmmmh I'm really sorry I don't have an oscilloscope... and even I don't know too well what it is... And I'm really not sure to find one here.... what an oscilloscope would tell me ?

Yes I have a diagnostic tool, a MSV-2 from Balckbox, the problem the module that are off are not always the same... sometimes seven of them are not giving an answer... but anyway i can check thourgh the seven, you are right.
How to check a module supply voltage ?
About earth I have checked many of them, they are all right, I don't have any corrosion under the seats and under the carpet... At least one good news !!!

Parrafin, really so so sorry about your health problem, I hope it will be nothing bad... I'm so sorry for you !!!

About the resistance measurment, it was on the PIN of the connector not of the Instrument Cluster, like I have written above.

I will write any news when I will go further...

Thank you to everyone and please Parrafin take care of you !!!!
  
Post #116364626th Sep 2013 9:11 pm
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Cellerdweller
 


Member Since: 05 Oct 2012
Location: Macclesfield
Posts: 1315

England 

Phifross

Yes the goal is to measure the the resistance of the canbus you must do this when it is not doing anything (no voltage ) . Yon can do this anywhere on the circuit and the easiest place is the 16 pin obd port .where you plug the Msv .
Maybe I've confused the issue by mentioning the oscilloscope it can be used to look at the can signal when it is being sent between modules on occasion I have seen a corrupt signal .however at this point it would appear from your description the integrity of the can lines is suspect . Or a faulty module is causing it .
If like I said one of the modules has a commas problem this is suspect . Check on your wiring diagram for any links between the module for example they share the same fuse or power source .
When you have a resistance of 60 ohms does the car work as it should ?
 You're not afraid of the dark are you ?  
Post #116366026th Sep 2013 9:33 pm
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Phifross
 


Member Since: 02 Feb 2013
Location: Monrovia
Posts: 31

Nigeria 2005 Discovery 3 4.4 V8 HSE Lux Auto Java BlackDiscovery 3
How to test a faulty module ?

Yes when I have 60ohm the car is working correctly, nothing is wrong...

How to know, or how to measure a faulty module ?
Please explain me well how to test a module...
I have a diagramm and I have already an idea about which module I have to test.

Thank you in advance.

Sorry these days internet is not good...

Thank you again !!!
  
Post #116520130th Sep 2013 7:43 pm
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Cellerdweller
 


Member Since: 05 Oct 2012
Location: Macclesfield
Posts: 1315

England 

Hi
If you suspect a particular module check on your wiring diagram and check the supply voltage + this will come from a fuse or possibly a relay also check the earth to the module it is possible the module shares it's earth with other things and if they are working I would initially assume the earth was ok . when you have 120 ohms and the car is not functioning you need to disconnect that module of the can ( providing it is one without a termination resistor in it . ) and see if the can comes back to life if it does re connect it to confirm your findings . Hope that helps Thumbs Up
 You're not afraid of the dark are you ?  
Post #116524130th Sep 2013 8:30 pm
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Phifross
 


Member Since: 02 Feb 2013
Location: Monrovia
Posts: 31

Nigeria 2005 Discovery 3 4.4 V8 HSE Lux Auto Java BlackDiscovery 3

If you suspect a particular module check on your wiring diagram and check the supply voltage + this will come from a fuse or possibly a relay also check the earth to the module it is possible the module shares it's earth with other things and if they are working I would initially assume the earth was ok . when you have 120 ohms and the car is not functioning you need to disconnect that module of the can ( providing it is one without a termination resistor in it . ) and see if the can comes back to life if it does re connect it to confirm your findings

Thank you for your explanations,


I need some more detail, sorry again, I'm a simple mind novice....

To check the supply voltage, it means I have to check the voltage when the module is connected, is it right ?
How to do so ?
Here are the modules that were missing:

SM129 INSTRUMENT PACK :- FITTED
SM129 PARK BRAKE MODULE :- FITTED

SM129 STEERING ANGLE SENSOR MODULE :- FITTED

SM129 ABS CONTROL MODULE :- FITTED

For example for the Park Brake module and the Steering Angke Sensor Module I didn't see any fuse... or did you mean a fuse in fuse box ?

Another question, where is the ABS control Module ?
And this one is the terminating module....

Instrument pack is the Instrument Cluster ?
For this one, how is possible to check the voltage when it is connected ? Really no idea about how to do it ?

Please help me with really detailed explanation about how to do that...

Thank you so much !!!!
  
Post #11658511st Oct 2013 9:51 pm
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