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

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kermit_rr said:
i dont think its the ecu :)
do you have a nanocom? sorry, i cant remember! that tells you if button presses are registered and what target speeds are set etc
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Yes, and the live data on nanocom says min speed reached/not reached correctly, the Set/Resume buttons are seen, the brake pedal switch statuses are seen target speed is seen, actual speed is reported. It just does not work. :vb-kaioken:

My last P38's Cruise was flawless, this is just a piece of pooh!
 
pwood999 said:
@DanClarke it's been a while, but did you ever get the AMR5700 working properly in your P38 ?

Pete
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Nope!
It sort-of works at 50MPH on the flat (just) i.e. low loading.
I will sometimes work at 70 (again..low loading).
It never accelerates once switched on and speed over the minimum limit.
It is $hit.
I can make it pass all the dognasties and can hot wire it to go full throttle on the drive... so all the vacuum stuff is good etc.
I have tried 3 AMR5700's (Original and 2 scrap/2nd-hands) but the values it offers as read by Nanocom are all not as per the manual and the readings are all wrong every time. I am stumped.
 
Just found this Tech Bulletin via google search. (cannot find it via forum search, but google link was this forum !!)

It seem for Disco II that LR suggest using the 4.0 tune in the cruise rather than the 4.6. Might help when using this ECU in P38 ?
 

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Even though I now have my cruise working again, I decided out of interest to get an AMR5700 & make the adapter loom. Luckily the ECU I ordered came with a Thor ECU plug, so the wire colours all match up.
 

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[Update] Installed the AMR5700 today, plus wired the diagnostic line so Nanocom can talk to it. It seems to work at 30mph, so will be trying it later today on the M3 to Ferndown.

Strangely in the settings screen, it allows Disco 4.0 & 4.6, plus Range Rover 4.6, but the RR 4.0 option says "No Data Available" ?

I'm wondering if LR put different tune selections in them with T4 depending on the target car, even though the part number is always AMR5700 ? Hence RR 4.0 would only be available in an ECU that was in a P38 from the factory.
 
Cruise working perfectly in my P38 4.6 GEMS with either ECU. Was able to swap back to the older ECU halfway, so got a comparison.

AMR1173: Now working perfectly since I re-soldered the PCB. Holds speed well, although the set button needs a good press to engage.
AMR5700: Slightly slower to accelerate, but it hold the speed steady with no problems. I had the RR 4.6 tune set in the ECU which should be correct. Also noticed my iPhone GPS speedo exactly matches the ECU speeds (within 1mph) but both don't display decimal point !! Instrument speedo shows 74mph when the cruise & GPS are showing 70mph !!

Same issue on both ECU's with set button slow to engage, so perhaps I need to look at that rather than the ECU's ?

Overall no real difference for me, so gotta decide which to leave installed in the car.
 
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