RRSCruiser wrote:

Hi

My faults were not the same as the OP, mine are/were detailed in my thread http://www.rrsport.co.uk/forum/topic46534.html

I fitted a brand new LR brake switch today, just elimnating any known causes and I also pulled the old switch apart and its identical to the first post with the arc marks and suspect contacts.

I just drove my car to a friends so it can be undercover for the next week whilst I try and go through all possible causes of these electronic gremlins. So far all undertrays off, ready to go through all wiring looms, plan to take out all the wheel arches so i can get to inspect the stuff under there. Also going to go through each ECU to check corrosion, pins and contacts, Iwill be buying a IID on monday to open the window to world the black box of landrover fault codes LOL

It may feel extreme but the car is near 10 years old, 134K, we love it and I plan to keep for some time yet so its a 10 year health check which hopefully clears up the gremlins that have appeared last week.

Just one bizarre observation tonight, when i parked up and did a few reverses in my friends garage ready for tomorrows strip down, I saw the transmission fault message, HDC off , special programs off. Basically all the faults that people were experiencing (but not me) and what this brake switch change has cured, in my case it has made them happen.

Thats a head scratcher for tommorrow, BIG glass of wine tonight in readiness

Any thoughts are most welcome

The hazards and door locking are symptoms of a CANBUS hissy fit. Thing to do is to check the wiring and ECUs as per your plan (diagnostic tools are, sadly, redundant when the CANBUS is down, though an IID is always worth having anyway), but firstly, have you checked the alternator voltage?  Visiting from DISCO3.CO.UK
2006 Discovery 3 TDV6 Auto HSE Zambezi Silver

Hi

Ive got the car at a friends in a lovely barn workshop and he has kindly let me have it there all this week through next weekend, so I can do the proper works to check as much as I can, progress thus far

The alternator was changed last week to another genuine LR YLE500430, the original alternator failed at 2011 with noisy bearings so this one has lasted circa 5 and a bit years
The battery was also changed last week under an RAC warranty as they put a new battery on in 2014 but its state of charge was low at 25%, this was after driving nearly 190 miles and having the vbattery on CTEK Mk7 charger

So hopefully my source power is good, I will be checking later in the week once the car comes back together

We had a gearbox flush, new metal sump and new sump filter, this has cured a slight judder which appeared for the first time at christmas, car has done 134K and gearbox never been changed but all other oils had been

We did have a rear bulb blow before christams and I put in two Bosch bulbs, best Halfrauds had at the time and I thought would be OK, its looking like not

I came across this thread on D3 site http://www.disco3.co.uk/forum/topic125274.html, I went to Eurocarparts this morning as they sell these OSRAM bulbs. I bought a box of 10 for �10, seemed a good deal. When i got to the car I checked the resistance with my meter and they were the same as the Bosch units I had installed and were all well below what the readings given by the thread had confirmed. I took them back and will be getting some genuine LR's tomorrow, I believe the number is XZQ000020. I will then check the resistance values from there.

I have progressively taken the car apart this weekend in aplanned way so i can achieve the following

1 - rule out any workmanship issue with all the work done by garages
2 - check and rectify any hidden water issues
3 - prove as much power, earths, connectros are good
4 - prove as much canbus and periperal wiring are good
5 - purchase a IID to look at whats going on in the black box of software, once stable look to use the update feature to get the modules at latest version

progrees thus far

I changed my brake light switch yesterday and it gave me the faults but I did have the bosch bulbs in, bizzare how this manifest. The switch I purchased was genuine LR so I'm hoping compatable and not faulty

All underneath protection off, both light clusters out, Instruemnt cluster out but connected for terminating resistors, Transfer module out of car, been metering out various cables and modules all day and found a few things already.

i) The battery -ve terminal was really tightened on the nut BUT the terminal could be rotated on the battery lug. On checking the taper was touching at the top so no amount of tighetening would make it clamp the lug. took about 30 seconds to lever out and create a consistent gap on the clamp which then could seat properly on the tapered battery lug and a nip up made it really firm

ii) The bulbs, the bulbs,

iii) Brake light switch, changed but will be checked again

iv) On transfer case module the upward facing pins had corrosion on them, i've opened the module and checked inside, all looks good and meters out for connectivity. No pins are corroded to the point they are suspect but the module power pin is the worst as it has lost its tinning and is showing copper/rust. The equivalent pin in the blue connector (centre one) is also showing copper colour, ie lost its tinning.

I plan to clean up the module pins and try to retin this one pin, the module will be reassemble and silicone sealed and the pins coated in vaseline for moisture

I have taken the Tyco reference for the connector (968271-1) and will try to get a new connector and pins so i can remake this connector for a 100% peace of mind. If I can't find a replacement, I can stay with what I have but its a doubt

I have checked the medium speed bus so far from the following; Parking sensor module, fuel burning heater, diagnostic socket, basically all the spurs and they are all circca 62 ohms and when i disconnect the Instruement cluster and lose one othe terminating resistors it goes up to circa 124 ohms, so behaving as expected for the wiring. I am not finished yet and hope to get it all checked

The High speed bus I have thus far only checked from the transfer case module and it is currently showing circa 120 ohms both sides so its seeing the terminating resistors

i will be checking for earths on these data lines

Once I've done all these static tests, conductivity and insulation (all with battery disconnected) then i will be powering up to do some voltage level checks with bus activity and then using the IID to start analysing things

It feels like a lot but I need this sorting ASAP and it will be a very good 10 year check on the car and will advance my knowledge massively as we do intend to keep this car, it is so nice and i love the V8

More to follow. I plan to write all this up with photo's Im collecting as i go, for mine and everyones benefit if you think that is a good idea?

[/list]

I got the IID BT unit yesterday and spent last night checking some things. Patrick at GAP has kindly offerred to help a novice with the fault codes in these initial reports

Attached is the report i sent to him, its a few lines but hopefully helps others if they are having similiar issues and any help/pointers that any members have in this will be grafetfully received.

The changing of the brakelight switch and fitting genuine LR bulbs has had the bizarre effect of now generating this HDC/Transmission/Special programs message when i lightly touch the brake pedal, :blub: :blub: :blub:

__________________________________________________________________________________



report 2 is the intermittent fault I had been chasing, reports 3 - 5 are a repeatable fault I can trigger by slightly touching the brake pedal when car is IGN on and either running or not - Is this related somehow

The cars problem is already written in my posts in the RRS.co.uk thread, attached here for background ( http://www.rrsport.co.uk/forum/topic46292.html ). All these issues didn't exist prior to the 4th Jan 2017, my username is RRSCruiser

Since Saturday the car has been powered down as I start this process of inspect, trace and rectify where needed.

In previous Autologic reports from the flushing garage and two from the RAC breakdown company scanning software (I have alll these in hard copy format and can scan them if it helps) they had identified a few times the transfer case (U0155), hence why I had a look

Last night I reinstalled the transfer case ECU which I had found with a corroded power pin (Blue plug, purple/blue tracer), it had metered out OK but needed some TLC. I opened the Ali case, no damage inside, no water ingress and no green corrosion inside. I sealed it with silicone sealant, I then cleaned up the power pin in the middle receiving socket and retinned the pin so it�s the same as the others and no bare copper to react and cause the green corrosion. On the car wiring loom I then got the pin out of the blue socket and cleaned it and found it also had lost its tin and hence why green corrosion was happening, all corrected with cleaning and retinning. In assembly I then used dielectric grease, to electrically insulate, protect from water and inhibit corrosion.

Summary

The intermittent fault (report 2) as described in the thread above occurred only once last night, it is appears unfortunately random and it has happened when driving after a short time, longer time, car ticking over and at different times of the day and journey time. This can all be better verified now with the IID as it time stamps what is happening and i can do some focused timeline analysis

The brake light switch and rear bulbs scenario (puzzling as i have changed switch and both bulbs - all genuine LR)is repeatable by briefly pressing the foot brake and results in some cases in a short duration message saying Transmission fault XXXX... which only appears on the LCD, creates a bing but no warning lights or any fault codes, in other cases it goes the full scenario of fault codes, messages and warning lights as per reports 3 onwards. Upto christmas eve we were running the same bulbs we had for year, one blew on a trip up north, I put in two Bosch bulbs of correct type all ssemd Ok for about 400 miles and then we didn't use car all christmas until we could get te gearbox flushed -- So is all this just bulbs and its finding the right ones that work with the car, bit ridiculous if it is!!!!!

I can make this brake pedal induced fault (reports 3 -5) happen repeatedly which will help resolve it

From the 5-previous fault code reads by others a few queries exist in relation to configuration anomalies that keep being repeated. Both garages have said they have not updated anything so puzzling at the minute as based on the very first Autologic baseline report none of these software incompatibilities had occurred in over 5 years of driving (basing this on last time fault codes were likely reset on the car (alternator changed in 2011)

The IID reports also the ECU�s it see�s and interestingly which ones it doesn�t see, this I need to find how to list and email as there are questions regarding units I know are fitted reporting they are not and from memory two ECU's that are fitted that say incompatible software?

There are about 5/6 (can�t remember) ECU�s with firmware reported as updates available, interestingly the Transfer case and transmission systems are showing up to date which the garages say they have not changed anything then I wouldn�t have anticipated these being up to date unless the current SW was released a few years ago and we had it updated as part of the 75K transfer box oil change we had done at a LR garage.

Do you have a list of release dates for the various software versions, this would help answer this question and rule out any software changes in this episode of faults??

This above comments on SW versions are based on a very quick look at this part of the IID functionality and a novice interpretation may be at work here��. LOL, happy to corrected here

One final observation, the HVAC fan seems noisier than I remember on full speed, almost sounds a little strained. Again, could be a red herring as the rear of car has all its trim out. Equally there are repeating faults regarding stepper actuators and flaps recording faults so further physical investigation needed and thinking it through these could affect the noise of the fan as air streams may be compromised, ??

Report 1

Here is the first report from the IID after connecting the battery, I am presuming this is mostly because car had been powered down and then a battery connected.

Info: The two rear brake clusters were out as I had purchased genuine LR bulbs and fitted a replacement genuine LR brake light switch, all as some findings on the RRS.co.uk forums and the issue generating SW fault messages. the car had been turned on so i could activate the IID and as part of that process it read these faults

VIN: SALLSAA237A106118
L320 � Range Rover Sport 2007
Vehicle scanned on 18-01-2017 19:56
Using IIDTool BT V3.0 B2444

Active Roll Control

U0155-87 (28) Lost communication with instrument cluster control module � Bus signal/message failure � missing a message
( on 17-01-2017 15:37:21 at 216992 km )
Audio System

U0010-87 (28) Medium speed CAN communication bus � Bus signal/message failure � missing a message
( on 17-01-2017 15:37:20 at 216992 km )
U0300-55 (68) Internal control module software incompatibility � System programming failure � is not configured
( on 17-01-2017 15:37:20 at 216992 km )
U2003-86 (28) Fibre optic communication bus � Bus signal/message failure � signal is invalid
( on 17-01-2017 15:37:20 at 216992 km )
Auxilary Heater

U3000-55 (2E) Control module � System programming failure � is not configured
Body Control

B1D06-15 (68) Left turn signal circuit � General electrical failure � circuit short to battery or open
( on 18-01-2017 19:27:52 at 216990 km )
B1D07-15 (68) Right turn signal circuit � General electrical failure � circuit short to battery or open
( on 18-01-2017 19:27:52 at 216990 km )
U0155-87 (28) Lost communication with instrument cluster control module � Bus signal/message failure � missing a message
( on 17-01-2017 15:37:20 at 216990 km )
U0300-55 (6C) Internal control module software incompatibility � System programming failure � is not configured
( on 17-01-2017 15:37:20 at 216990 km )
Engine TDV8

U0416-00 (28) Invalid data received from vehicle dynamics control module
Instrument Pack

U0132-87 (2C) Lost communication with ride level control module � Bus signal/message failure � missing a message
U0182-87 (2C) Lost communication with front lighting control module � Bus signal/message failure � missing a message
U0159-87 (2E) Lost communication with parking assist control module � Bus signal/message failure � missing a message
U0184-87 (2C) Lost communication with audio unit � Bus signal/message failure � missing a message
B1A87-68 (2C) Battery disconnection/electronic control unit reset � Algorithm based failure � event information
Navigation

B110E-25 (6C) Tailgate double locking motor � General signal failure � signal shape/waveform failure
( on 18-01-2017 02:55:47 at 10637059 km )
Parking Aid

U0155-87 (28) Lost communication with instrument cluster control module � Bus signal/message failure � missing a message
U0140-87 (28) Lost communication with body control module � Bus signal/message failure � missing a message
U0300-55 (28) Internal control module software incompatibility � System programming failure � is not configured
Parking Brake

U0122-87 (A8) Lost communication with vehicle dynamics control module � Bus signal/message failure � missing a message
( on 18-01-2017 19:27:13 at 216998 km )
C1A00-16 (A8) Control module � General electrical failure � circuit voltage below threshold
Steering Angle

U0122-87 (28) Lost communication with vehicle dynamics control module � Bus signal/message failure � missing a message
( on 17-01-2017 15:37:25 at 216992 km )
Transfer Case

U0155-87 (28) Lost communication with instrument cluster control module � Bus signal/message failure � missing a message
( on 17-01-2017 15:37:21 at 216992 km )
Transmission

U0155-87 (6D) Lost communication with instrument cluster control module � Bus signal/message failure � missing a message
( on 17-01-2017 15:37:21 at 216992 km )
Ventilation

B1B74-00 (2C) Front foot-defrost mode stepper actuator
( on 16-01-2017 13:49:21 at 216974 km )
B1B75-00 (6C) Front foot-face mode stepper actuator
( on 16-01-2017 13:49:22 at 216974 km )
B1B76-00 (2C) Front left air blend stepper actuator
( on 16-01-2017 13:49:22 at 216974 km )
B1B77-00 (2C) Front right air blend stepper actuator
( on 16-01-2017 13:49:22 at 216974 km )
B1B78-84 (2F) System pressure � Bus signal/message failure � signal is below allowable range
( on 16-01-2017 12:09:52 at 216974 km )
End of report 1

------------------------------------------------------------------------------------------------------------------------------------

I then fitted the rear brake clusters with the genuine LR bulbs, using the IID I reset the faults and left the car running. It was a very cold night (-2degC)

The fault occurred after about 10 mins of tick over, I scanned the car and added the text to the mail to record the following (All very neat, well done)

Report 2

Text from email

Put Landover bulbs in

Car running about 10 mins

Then this happened and wouldn't reset � always reset previously after about 30 seconds, only difference I can see is the HVAc blower was turned right down and the OFF was selected

Sat across radio stay off display stayed off with --hazard flashers on DSC/suspension lamp on amber

Car temp gauge stay at bottom but fan keeps cycling on in engine � this was just a timing issue as the gauge went up as the car progressively got warmer

HVAC blower was off, I turned it on and the radio came back on then satnav then in display flashers stopped just left DSC/suspension lights

VIN: SALLSAA237A106118
L320 � Range Rover Sport 2007
Vehicle scanned on 18-01-2017 20:11
Using IIDTool BT V3.0 B2444

Active Roll Control

U0155-87 (AF) Lost communication with instrument cluster control module � Bus signal/message failure � missing a message
( on 18-01-2017 20:10:37 at 216998 km )
Audio System

U0010-87 (AB) Medium speed CAN communication bus � Bus signal/message failure � missing a message
( on 18-01-2017 20:10:36 at 216998 km )
Auxilary Heater

U3000-55 (2F) Control module � System programming failure � is not configured
Body Control

U0155-87 (2F) Lost communication with instrument cluster control module � Bus signal/message failure � missing a message
( on 18-01-2017 20:10:36 at 216990 km )
U0300-55 (2F) Internal control module software incompatibility � System programming failure � is not configured
( on 18-01-2017 20:10:36 at 216990 km )
Parking Aid

U0155-87 (2F) Lost communication with instrument cluster control module � Bus signal/message failure � missing a message
U0300-55 (2F) Internal control module software incompatibility � System programming failure � is not configured
Steering Angle

U0122-87 (2F) Lost communication with vehicle dynamics control module � Bus signal/message failure � missing a message
( on 18-01-2017 20:10:41 at 216998 km )
Transfer Case

U0155-87 (2F) Lost communication with instrument cluster control module � Bus signal/message failure � missing a message
( on 18-01-2017 20:10:37 at 216998 km )
Transmission

U0155-87 (2F) Lost communication with instrument cluster control module � Bus signal/message failure � missing a message
( on 18-01-2017 20:10:37 at 216998 km )
Vehicle Dynamic

U0155-87 (2B) Lost communication with instrument cluster control module � Bus signal/message failure � missing a message
( on 18-01-2017 20:10:38 at 216998 km )
Ventilation

B1B78-84 (6C) System pressure � Bus signal/message failure � signal is below allowable range
( on 18-01-2017 20:08:44 at 216998 km )
End of report 2

------------------------------------------------------------------------------------------------------------------------------------

I reset the car with IID and then turned off and on as the Satnav screen had stayed with the LR logo and would not respond to any keypresses

Report 3

Text and photo from email

Engine running, HVAC off, car on high suspension

Pressing foot take, turning steering wheel about 50-100mm and HVAC fan on lowest setting and toggling off and on

HVAC, steering wheel and high suspension may be red herring as later repeated tests and could generate this fault scenario with only touching the brake pedal

Get these faults lights, see attachment photo



VIN: SALLSAA237A106118
L320 � Range Rover Sport 2007
Vehicle scanned on 18-01-2017 20:48
Using IIDTool BT V3.0 B2444

Engine TDV8

U0416-00 (2F) Invalid data received from vehicle dynamics control module
Transmission

U0416-86 (2F) Invalid data received from vehicle dynamics control module � Bus signal/message failure � signal is invalid
( on 18-01-2017 20:48:16 at 134836 mi )
Vehicle Dynamic

C1A96-62 (2B) Brake lamp switch circuit � Algorithm based failure � signal compare failure
( on 18-01-2017 20:48:15 at 134836 mi )
Ventilation

B1B78-84 (2F) System pressure � Bus signal/message failure � signal is below allowable range
( on 18-01-2017 20:47:28 at 134836 mi )
End of report 3

------------------------------------------------------------------------------------------------------------------------------------

I then reset the car with IID, I think the fault lights and codes would not reset with the car still running so I turned off and on and all was clear, started car

Report 4

Text from email

Same IC indicators as report 3

Engine running

On high suspension

Just press foot brake a couple of mm, triggers same fault

VIN: SALLSAA237A106118
L320 � Range Rover Sport 2007
Vehicle scanned on 18-01-2017 20:54
Using IIDTool BT V3.0 B2444

Engine TDV8

U0416-00 (2F) Invalid data received from vehicle dynamics control module
Transmission

U0416-86 (2F) Invalid data received from vehicle dynamics control module � Bus signal/message failure � signal is invalid
( on 18-01-2017 20:53:54 at 134836 mi )
Vehicle Dynamic

C1A96-62 (2B) Brake lamp switch circuit � Algorithm based failure � signal compare failure
( on 18-01-2017 20:53:51 at 134836 mi )
Ventilation

B1B74-00 (2F) Front foot-defrost mode stepper actuator
( on 18-01-2017 20:53:37 at 134836 mi )
B1B75-00 (2F) Front foot-face mode stepper actuator
( on 18-01-2017 20:53:38 at 134836 mi )
B1B76-00 (2F) Front left air blend stepper actuator
( on 18-01-2017 20:53:37 at 134836 mi )
B1B77-00 (2F) Front right air blend stepper actuator
( on 18-01-2017 20:53:37 at 134836 mi )
B1B78-84 (2F) System pressure � Bus signal/message failure � signal is below allowable range
( on 18-01-2017 20:53:25 at 134836 mi )
End of report 4

------------------------------------------------------------------------------------------------------------------------------------

Again, turned car off and on to clear down faults after trying the reset all faults on IID, set suspension to normal height and car on tick over

Report 5

Text from email

Normal height

Engine running

Just touching brake pedal

VIN: SALLSAA237A106118
L320 � Range Rover Sport 2007
Vehicle scanned on 18-01-2017 20:58
Using IIDTool BT V3.0 B2444

Engine TDV8

U0416-00 (2F) Invalid data received from vehicle dynamics control module
Transmission

U0416-86 (2F) Invalid data received from vehicle dynamics control module � Bus signal/message failure � signal is invalid
( on 18-01-2017 20:58:13 at 134836 mi )
Vehicle Dynamic

C1A96-62 (2B) Brake lamp switch circuit � Algorithm based failure � signal compare failure
( on 18-01-2017 20:58:11 at 134836 mi )
Ventilation

B1B74-00 (2F) Front foot-defrost mode stepper actuator
( on 18-01-2017 20:57:29 at 134836 mi )
B1B75-00 (2F) Front foot-face mode stepper actuator
( on 18-01-2017 20:57:30 at 134836 mi )
B1B76-00 (2F) Front left air blend stepper actuator
( on 18-01-2017 20:57:29 at 134836 mi )
B1B77-00 (2F) Front right air blend stepper actuator
( on 18-01-2017 20:57:29 at 134836 mi )
B1B78-84 (2F) System pressure � Bus signal/message failure � signal is below allowable range
( on 18-01-2017 20:57:19 at 134836 mi )
end of report 5

------------------------------------------------------------------------------------------------------------------------------------

Have you got a good voltage on the red wire to the brake switch? Visiting from DISCO3.CO.UK
2006 Discovery 3 TDV6 Auto HSE Zambezi Silver

Hi

Yes I will be checking this, I was sorting a corroded power pin on the transfer case ECU first

Patrick at GAP, he has read the above reports and fed back some supereb advice on 2 issues I may be dealing with

This brake switch/lamps is the first and I set about it last night, did a live value read with the IID and got the attached chart which shows the brake pedal being pressed, both lamp circuit and Brake switch are meant to match near enough. First two presses OK, third press got the HDC, Transmission, special programs fault all as per the OP issue and you can see that the switch signals did not match, brilliant and didn't need to take trim off.

I did then take the trim off as yes I am now tracing wires to make sure if the brand new LR brake switch is the issue or the cabling or the power etc

I got distracted with the car then producing the intermittent fault unprompted aand just tiocking over, everything happened as before as I described in my thread post but the difference was the fault stayed there, only difference I could see was the HVAC fan was turned to minimum. It stayed as the fault ie all shut down on satnav/.radio and hazrds but the HVAC unit kept turning on and off (seen by the off lamp illumination. I gathered information on this with observation, IID scanning and watching live values.

When i noticed the HVAC unit was back on line I turned the fan switch up to setting speed 3 and the hazards stopped flashing, the HVAC unit stopped cycling but the satnav and radio did not recover this time and stayed blank until I had finished all the info gathering and turned car off, waited then back on and alll was clear again ) I did a final fault read and reset faults when turning car off and on to reset it

I can hear the HVAC fans being much louder, but that may be the actuators faults - Dont know yet just starnge that the HVAC fan dial can have an affect on this intermittent fault

Real head scratcher here, from no issues for years to this all starting about the time I had the gearbox flushed and a new sump pan and filter fitted, really puzzling

Hi

Started this morning on the brake switch and found

Battery voltage 12.34V on battery terminal
Red wire on brake lamp switch 11.42v with no load ie switch disconnected

Checked and getting a 42ohm resistance to ground on this cable, which could be the reverse relay. It says it in the CJB, I cannot find it to unplug and prove this assumption

Now spent a while trying to find this relay, am i looking in the correct palce and does anyone know where it is?

Its designated as R217 but again can't see this anywhere on any legend sticker

Did a lot of tracing yesterday, summary

Brand new Genuine LR Brake lamp switch was faulty, I got another one from Advanced factors as a backup but for now I have reinstalled the original one that came with the car. I had took this apart and cleaned it down and its working perfectly. I cannot get the HDC/Trans fail... fault to recreate and also the IID shows a perfectly synced pulse on both circuits (Brake lamps and ABS input), progress

Now the weird stuff, the volt drop is still present on the red wire, so I am losing about 0.9-1v somewhere (couldn't find the reverse relay, to verify the 41ohms is from this, still looking though)

What i did see on the IID is the voltages are showing a fluctuation, I have no previous experience here so it may be normal but it made me look at the following, starting with the grounds

Battery off, disconnected the Instrument pack (IPC) and metered the ground (pins 31 & 32) To refernce I used my heavy duty jump leads to go directly to the battery and bring this reference point round to the drivers seat. This resistance was subtracted from all readings taken so I am quoting values from the circuits in the car

On pins 31 & 32 they go to earthing point C2628-1, in the driver footwell area, the battery lead connects to the body in the left hand wing close to teh battery.

With the battery connected back up, but no IPC connected so i can meter at the pins for now

Keys out of ignition - pin 31 or 32 read 0.2ohms back to battery -ve
Key in ignition not turned, car starts bleeping - 0.2 ohms still
Key turned to pos I - 0.2 ohms still
Key turned to pos II - reading jumps up to around 16ohms, fluctuating then drops to 2 ohms then up again ????

Now doing some ohms law, if my volts are circa 14v and this resistance is around 16 ohms, I get my 0.9V volt drop on the red pin

This feels wrong as the circuit (using car body) should stay same on the ground side even as other items in car are powered up when the key gets to pos II, please correct if I'm wrong

Few more hours burnt getting info together, stopped at 6pm when temp hit -3 deg, nearly 10 hours in cold is even for most people.

I talked this through with my Dad last night (retired Auto electrician) and he acknowledged this era of electronics in the sport is later than his years but the basics of car power has changed only slightly. An possible explanation could be poor earths, main earths from the battery through to the car. These connections could read OK when no current is flowing from other components but the resistance could increase as current starts to flow thus disturbing this IPC ground circuit

I am this morning getting teh car on ramps and checking all earth points (that I can find), especially the ones that may have been disturbed when the engine/gearbox was lifted slightly to facilitate the sump & filter chage at the gearbox flush.

This feels a punishing process, steep learning curve in fault finding the car as so much is interconnected, software driven and great when working but when its not....

Thanks so far, to my friend for use of his barn, Patrick at GAP in explaining what the tool can do, how to interpret the findings, my Dad for his wisdom and these forums in both their direct comments and the historical threads which are a goldmine in information and past journeys through these type of issues, long may it continue

Any thoughts more than welcome, I am using this diagram to find earth points, if anyone has more info then please could you share