Disco 3 (LR3) Steering Angle Readings....Curious!

lynall said:

Cannot beat a load/bulb test on wiring.

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many thks and indeed found out the hard way with regards to load testing , seeing it passed on a multimeter and failed using a conventional test light that had a simple bulb , remembered ur goodself and @sierrafery talking about load testing and how important it was loading a circuit over a multimeter

also learnt another way to test a ground point this time using a multimeter was , ignition on then measuring the voltage between the grounding point and the negative battery terminal and seeing if it was below 0.2Vdc

apologises if you’ve already seen this @Saint.V8 , as found the canbus connector between the yaw sensor and ABS module , ref 2245 and 2243

plus looking at the high and low canbus connections if thats another resistor where the yaw canbus joins onto the ABS module at pins 25/45 connector co506

Plus very curious on why it has a maximum 500mm on those earth connections plse

gstuart said:

As a side note I Must confess I got caught out a few times when testing continuity

Passed using a multimeter and the same with a test light that had a LCD display , However it failed using a test light fitted with a conventional bulb , assume it was because I put the system under load due to the bulb

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Yes, there are cases like that

gstuart said:

Plus very curious on why it has a maximum 500mm on those earth connections plse

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Cos some ECUs are very sensitive to voltage drops so IMO it's about keeping the earth's resistance as low as possible, for example in the D2's Wabco ABS module description there are these two notes:
* TOTAL RESISTANCE INCLUDING CONTACT AND CRIMP RESISTANCE: R<0.017 OHMS for the connection which gives the main earth(that big earth connector below the multiplug
**TOTAL RESISTANCE INCLUDING CONTACT AND CRIMP RESISTANCE: R<0.04 OHMS on the refference earth(ground) circuit from SLABS to pin 8 of multiplug and if the resistance is higher than that it triggers a fault code... might be something similar here too.

There is a terminating resistor in the Yaw Sensor and a second i nthe ABS module as the Yaw Sensor is connected to the ABS sensor via its own mini CANbus....

120Ohm reading was because Ihad the TCCM disconnected which took the ABS Terminating Resitor out of the equation!

I have a couple of extra videos to post which I will do in the morning, which shows some strange voltage readings being taken on the CAN....

Oh these cars are such fun.

gstuart said:

Plus very curious on why it has a maximum 500mm on those earth connections plse

View attachment 287596

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They could be longer, but they'd need to be of a thicker gauge to keep the volt drop down to an acceptable level. As that involves more copper, it also mean more cost, which the bean counters won't like.

sierrafery said:

Cos some ECUs are very sensitive to voltage drops so IMO it's about keeping the earth's resistance as low as possible, for example in the D2's Wabco ABS module description there are these two notes:
* TOTAL RESISTANCE INCLUDING CONTACT AND CRIMP RESISTANCE: R<0.017 OHMS for the connection which gives the main earth(that big earth connector below the multiplug
**TOTAL RESISTANCE INCLUDING CONTACT AND CRIMP RESISTANCE: R<0.04 OHMS on the refference earth(ground) circuit from SLABS to pin 8 of multiplug and if the resistance is higher than that it triggers a fault code... might be something similar here too.

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Spong said:

They could be longer, but they'd need to be of a thicker gauge to keep the volt drop down to an acceptable level. As that involves more copper, it also mean more cost, which the bean counters won't like.

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Thks so much , funny enough it reminds me of fitting an extra hot water tank on underfloor heating in using it as a buffer tank which stops the boilers thermostat from cycling on and off as the temperature rises and falls , so acts like a cushion so to speak

hopefully I’ve understood it correctly as by that I wonder if adding extra earths could have upset the system by having longer earth connections from the battery to other modules , apologises @Saint.V8 if u haven’t done that

also would this kind of test be beneficial or no point plse

turn the ignition on
multimeter set to Vdc
one test probe onto the negative battery post ( found using mole grips very handy for this )
then with the other test probe going round every grounding body point including grounds going via connectors to ensure it’s not above 0.2 Vdc

also before I forget Ive come across bad wires inside connectors , so learnt to put a test light on both sides one by one , sometimes back probing them to ensure the feeds or earths are going through the connector and hasn't got bad pins or connection , hope that makes sense

daft question if I may plse , if using a very long multimeter lead to reach varies positives / earths could u get a false reading by doing so plse, many thks and hope u didn’t mind me asking

once again big apologises if that’s already been done

know all of us have got our fingers crossed that the issue will soon be resolved along with keeping ur sanity my friend

Yesterday I took some time to run some tests on the CAN - it is a long video where I disconnect everything from the CAN and one at a time connect an ECU and restest the voltage, then disconnect that and connect another one etc etc....so it took a short while - the vid is abot 37 minutes



TLDR: All seems well until the EPB which is when the Voltages do something different instead of 2.43 (HSCAN L) and 2.53 (HSCAN H) with everyhing else it goes to 2.35 (HSCAN L) and 2.61 (HSCAN H) when it is plugged in. I tried another EPB module and the same thing happened....curious!!!

I also checked the connections behind the Pax rear wheel and they are super clean and the wiring is intact.



And they look fine - I wonder if it could be the wiring to the EPB?

And also, how could a dodgy EPB affect the Yaw Sensor considering they are on a separate network and never the twain shall meet??

All earth points check out too and the EPB works well and no issues to report???

Other than this yaw Rate Sensor reading the car works well - obviously I have no Terrain Response or traction control and warning lights on the dash.....and a couple of modules report 'Invalid Data received from the Vehicle Dynamics Control Module' because the Yaw Sensor readings are so ridiculous I am getting to the end of my knowledge now

Confused dot com comes to mind!

I have always worked on roughly 2.5 volts is near enough to prove the system is working.
Other important thing I check is the earth for that particular ECU/CAN set up, as a lot of the exhaust kit is remote and has 4 wires 2xCAN 1xvolt pos and 1xvolt neg, I always ues the supplied neg for testing that particular set up whcih are normally nox sensors.
So in the case of the Nox sensors if the CAN and volts check out the sensor or sensor ecu (all one unit) are duff.

Iirc there was a recall early on in the D3s life with some of the EPB wiring running along the chassis right next to the compressor causing issues, where the recall involved some sort of splice/repair which later on fails.

Saint.V8 said:

Yesterday I took some time to run some tests on the CAN - it is a long video where I disconnect everything from the CAN and one at a time connect an ECU and restest the voltage, then disconnect that and connect another one etc etc....so it took a short while - the vid is abot 37 minutes



TLDR: All seems well until the EPB which is when the Voltages do something different instead of 2.43 (HSCAN L) and 2.53 (HSCAN H) with everyhing else it goes to 2.35 (HSCAN L) and 2.61 (HSCAN H) when it is plugged in. I tried another EPB module and the same thing happened....curious!!!

I also checked the connections behind the Pax rear wheel and they are super clean and the wiring is intact.

View attachment 287857

And they look fine - I wonder if it could be the wiring to the EPB?

And also, how could a dodgy EPB affect the Yaw Sensor considering they are on a separate network and never the twain shall meet??

All earth points check out too and the EPB works well and no issues to report???

Other than this yaw Rate Sensor reading the car works well - obviously I have no Terrain Response or traction control and warning lights on the dash.....and a couple of modules report 'Invalid Data received from the Vehicle Dynamics Control Module' because the Yaw Sensor readings are so ridiculous I am getting to the end of my knowledge now

Confused dot com comes to mind!

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Hi there. Have you ever resolve this issue as I have exactly same problem with my Disco 3 which I battling for over a month now.. Absolute nightmare this car is I telling you.. Thanks in advance. Martin

MarcinW said:

Hi there. Have you ever resolve this issue as I have exactly same problem with my Disco 3 which I battling for over a month now.. Absolute nightmare this car is I telling you.. Thanks in advance. Martin

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Hi Martin,

Never did get to the bottom of this one - in fact, thanks for reminding me of this post...I guess I should close this out.

Despite changing the EPB, ABS Module, SAS, Yaw Sensor, remaking all the wiring, giving it a new power feed and ground, changing the Transfer Case Module for a coded replacement.....I could not figure out why it kept giving Yaw Sensor and Lateral Acceleration sensor faults....no matter what I did.

Unfortunately, the demise of the vehicle was a split Cross Over Pipe, the EPB kept faulting despite new cables, module, back plates, shoes and links (all fitted and adjusted correctly), needed 2 rear tyres, oil pressure on start up would take 4-5 seconds for the pressure light to go out so it would need a new oil pump, might as well do the water pump and timing belt while in there, as well as the rear fuel pump belt.

It was costing us near £700 a year in tax and drank fuel like a thirsty fish - so we bit the bullet at the beginning of December and passed it on.....so I am Landy-less at the moment (which sucks) but right now, it is nice not to have to worry about it going wrong again, and pounding more cash on something that at the end of the day was to expensive to run, tax and had a limited lifespan left.

Best of luck with yours Martin - they are fantastic cars that will test the patience of many.....if you find out your issues, do post your resolve as it will massively help others.

Saint.V8 said:

Hi Martin,

Never did get to the bottom of this one - in fact, thanks for reminding me of this post...I guess I should close this out.

Despite changing the EPB, ABS Module, SAS, Yaw Sensor, remaking all the wiring, giving it a new power feed and ground, changing the Transfer Case Module for a coded replacement.....I could not figure out why it kept giving Yaw Sensor and Lateral Acceleration sensor faults....no matter what I did.

Unfortunately, the demise of the vehicle was a split Cross Over Pipe, the EPB kept faulting despite new cables, module, back plates, shoes and links (all fitted and adjusted correctly), needed 2 rear tyres, oil pressure on start up would take 4-5 seconds for the pressure light to go out so it would need a new oil pump, might as well do the water pump and timing belt while in there, as well as the rear fuel pump belt.

It was costing us near £700 a year in tax and drank fuel like a thirsty fish - so we bit the bullet at the beginning of December and passed it on.....so I am Landy-less at the moment (which sucks) but right now, it is nice not to have to worry about it going wrong again, and pounding more cash on something that at the end of the day was to expensive to run, tax and had a limited lifespan left.

Best of luck with yours Martin - they are fantastic cars that will test the patience of many.....if you find out your issues, do post your resolve as it will massively help others.

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Thank you so much for such a quick reply. Also as I very rarely give up I'll try my best find the problem and will post here whatever I find. Thanks again