P38A Cruise Control - Armchair theorists required for ideas and help.

Apart from very steep hills, comparing to SatNav speed mine is within +/- 1mph of the setting. It seems quite a few have reported lots of speed variation . . .. maybe I'm lucky ?

pwood999 said:

Apart from very steep hills, comparing to SatNav speed mine is within +/- 1mph of the setting. It seems quite a few have reported lots of speed variation . . .. maybe I'm lucky ?

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Cruise works well on the diesel

nigelbb said:

I find the cruise control on my 2001 Vogue is functional but pretty crude compared to the cruise control on my 2006 Jaguar S-type. The cruise control on the Jag allows me to tap +/- buttons to increase/decrease speed & keeps to the set speed much better than the P38 which can hover around by a few mph either side of the set speed.

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Was like that on my old Merc 500 SEL (lovely car).

UPDATE:
I connected up the Nanocom and while it is as flaky as a Greggs Sausage Roll with respect to connecting to the ECU (You have to have several goes from ground-Zero) it tells me a lot.
The Values set within the ECU are mixed between two engine sizes.
Some are set as if its a 4.0Ltr others at the values for a 4.6Ltr.
While the Vehicle Tune setting says 4.6 Engine the values elsewhere are not correct for a Range Rover.
The "Minimum Threshold" detection works but the display is reversed (when you are stationary it says "Threshold Met" and when you are doing over 28MPH it says "Threshold Not Met" so that's just a foible of Nanocom I think.
All the brake & brake-light values toggle wit the pressing of the brake pedal, and the Set/Resume switches are detected as "Pressed" or "Not pressed".
Road speed detection is perfectly fine.
Target Speed setting changes depending on how fast you are going when you press the "Set" button.

So, I need to see if anything changes if I select another Engine Type although the manual says there are 5 types including "Range Rover 4.6" this item does not actually appear in the available choices accessed through Nanocom only "4.6 Engine" and the values under this setting are a mish-mash of the values for various vehicle types. Basically its carp.
I have another ECU, and maybe I should try that (but I haven't a clue where I have put it ).

Might be worth posting on Nanocom Forum as well. BBS will get back to you at some point.

Maybe program it with the values from the Nanocom for your engine, and see how it behaves ?

BTW, on Nano Forum, there's one post where Adrian suggested using the D2 > V8 > CC menu route to get into the ECU. He also said you might need to press "Set" button after ignition is on, to enable communication to start !!

pwood999 said:

Might be worth posting on Nanocom Forum as well. BBS will get back to you at some point.

Maybe program it with the values from the Nanocom for your engine, and see how it behaves ?

BTW, on Nano Forum, there's one post where Adrian suggested using the D2 > V8 > CC menu route to get into the ECU. He also said you might need to press "Set" button after ignition is on, to enable communication to start !!

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Thanks @pwood999 ... Sadly all the values are not editable, you can only select a "Tune Map" from the 5 there are in the ECU.
The ECU unpacks the values and displays them, but you cannot edit/change/update them.
And... I cannot find my spare AMR5700 ECU.

It would be interesting to see if any of the "Tune Maps" match the numbers in the Nanocom guide ? Most likely you would have to write the new setting, and then exit & do ignition off-on for it to load. If none match, then either the ECU is corrupted, or someone has been messing with the internals ?

They are cheap enough on eBay. I would buy another spare.

pwood999 said:

It would be interesting to see if any of the "Tune Maps" match the numbers in the Nanocom guide ? Most likely you would have to write the new setting, and then exit & do ignition off-on for it to load. If none match, then either the ECU is corrupted, or someone has been messing with the internals ?

They are cheap enough on eBay. I would buy another spare.

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I did try all of the "Tune Maps" and none of them match the printed figures completely.
Some maps fix one characteristic but completely fail on another and it is all a hotch-potch.
So, I have (as you suggest) taken pot-luck on an e-bay purchase from a breakers.

Another thought that occurs to me is that all the inputs and triggers seem to be present but nothing is getting to the vacuum pump. Now while I can manually stuff earth and 12v on the relevant pins and get it to chooch properly, maybe an earth or Volts line is broken and the controller etc. is all doing it's part but the juice/earth is NOT getting through to the vacuum pump unit because of a disconnected/broken wire/connector.

DanClarke said:

Another thought that occurs to me is that all the inputs and triggers seem to be present but nothing is getting to the vacuum pump. Now while I can manually stuff earth and 12v on the relevant pins and get it to chooch properly, maybe an earth or Volts line is broken and the controller etc. is all doing it's part but the juice/earth is NOT getting through to the vacuum pump unit because of a disconnected/broken wire/connector.

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I would have thought if it was case of broken wire then it just wouldn’t work at all rather than working at 50mph and not below.

Khemitude said:

I would have thought if it was case of broken wire then it just wouldn’t work at all rather than working at 50mph and not below.

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Yes, it is very puzzling as to why it "tries" at 50/55 but fails in all other respects.

Dry joints on the PCB, or failing capacitors ? I had to do some repairs on the older Cruise ECU on my GEMS.

Can you put pins Into the cc plug, stick a dvm on the wipers and drive it just over 30mph and monitor the voltage? Or am I passed this part of your diag?

nigelbb said:

I find the cruise control on my 2001 Vogue is functional but pretty crude compared to the cruise control on my 2006 Jaguar S-type. The cruise control on the Jag allows me to tap +/- buttons to increase/decrease speed & keeps to the set speed much better than the P38 which can hover around by a few mph either side of the set speed.

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The most annoying feature with mine is overshooting the set speed when pressing RES. When running it holds the set speed tightly on the level or a mild incline but can run overspeed downhill as it only adjust the accelerator & cannot give a dab on the brakes so you can inadvertently exceed the speed limit despite being set lower.

Don't forget, you can get the thor remapped, i can't remember who does it, but maybe that explains the data you're seeing?

Replacement AMR5700 ECU (allegedly from a 4.6 P38) ordered from a breaker.
Should be here next week.
The live data from the Nanocom does take a lot of the MAP chart jiggery-pokery out of the equation because the ECU reports what it is seeing/being told. So that was a great tip, thanks. Reading the settings in the replacement ECU may confirm that this one is nadgered.
Edit: Oops told you most of this already.

DanClarke said:

Replacement AMR5700 ECU (allegedly from a 4.6 P38) ordered from a breaker.
Should be here next week.
The live data from the Nanocom does take a lot of the MAP chart jiggery-pokery out of the equation because the ECU reports what it is seeing/being told. So that was a great tip, thanks. Reading the settings in the replacement ECU may confirm that this one is nadgered.
Edit: Oops told you most of this already.

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Let us know how you get on especially if one it’s on it holds true, might worth looking into on mine if it works on yours.

Though part of me wonders if it could have something to do with the cam I’ve got on mine, I believe it’s a pipercross so assuming it’s making a touch more power then I wonder if the cc unit thinks hang on I’ve got to much rpm and backs off then puts more on overshooting a little ad nauseam

Edit: Just read this on another forum and kinda makes sense

The CC units are tuned to match their motors. So, if you got a CC unit for a 4.6L, it will not have as much gain as one for a 4.0. Then if the 4.6 CC is installed in a 4.0 truck, it will seem very sluggish because it won't move the throttle at the tuned rate to respond to an error in speed. Conversely, if a 4.0 CC unit is installed in a 4.6 truck, it will tend to surge and overshoot.

When I use CC, I compensate somewhat by giving a couple clicks up after hitting set, before I completely release the gas pedal. That helps it catch. On occasional hills (highway not mountains), I just accept that it's going to slow down and take a while to ramp back up to speed. Make sure the hook for the CC actuator is barely off the throttle closed position. Too much gap there will mean the actuator won't be able to pull as far.

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Cannot find if the Motronic ECU for Thor has 4.0 / 4.6 selection, or if LR used different Part No. vs firmware coding ? (GEMS does have 4.0 / 4.6 option, which impacts engine performance & hence cruise acceleration).

Also remember the cruise & engine ECU diagnostic line are connected together, so theoretically they could talk to each other, although this is not mentioned in RAVE or Nanocom guides ?

The Hella guide is very definite that the "Tuning" you choose from the available types is unpacked to populate all the fields referenced elsewhere in the guide. What I found "ODD" was that none of the available options (when selected) resulted in the sets of values the guide declared for each setting, it was all a messed-up mix. Not only that, but there was NO Range Rover 4.6 option (as suggested in the guide). Now, it is possible that my Hella ECU has been hacked/messed-up somehow by someone (not me). I don't think there is much point in me documenting all the settings that each "Tuning" choice results in because it just isn't working for me. When the "new" (to me) one arrives and I install it, I will document all of its settings (per tuning that is selected) if it fixes my problem. - Promise!

UPDATE:
New (2nd hand) ECU arrived and fitted. Fault still not fixed.
Exactly the same as with original ECU.
There is no Range Rover 4.6 option in the Tune Settings (whereas the Black Box Hella CC document says there is).
There is only the following set of choices:
* ECU Default
* 4.6 Engine
* Range Rover 4.0
* Discovery II 4.0
* Unknown
I have tried the 4.6 Engine and the unpacked values do not match those documented for the mythical Range Rover 4.6.

So I am no further forwards, and cruise-control is still not working.