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P38A Is my mojo rising..... or do I need a new Driver Board?

Discussion in 'Range Rover' started by DarthDude, Jan 15, 2021.

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  1. wammers

    wammers STILL BREATHING. Donater

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    The delay relay switches on the ECU every six hours to self level, the car can only level downwards. The only possible way the car can rise is high pressure stored air leaking past the inlet valve and forcing past the corner valves with the gallery exhaust closed. Your problem is finding how this is happening.
     
  2. DarthDude

    DarthDude Well-Known Member

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    Yes.... and how it's happening with the battery connected but NOT happening when the battery is disconnected.

    The current assumption is that something is allowing current to leak into the inlet and airspring valve solenoids when there's current to be had (i.e. when there's a battery present) and since there's only 2 things that can do that- driver board and ECU- then it's either one or both of these that's the cause of my problems.

    Is that a fair assessment? Or is the delay relay still in play?
     
  3. wammers

    wammers STILL BREATHING. Donater

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    The delay relay could be switching more often than it should the ECU could be switching the wrong parts of the driver pack or the driver pack could have failed. All should be checked and illiminated.
     
  4. DarthDude

    DarthDude Well-Known Member

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    The delay relay can switch on as often as it likes but if the ECU is not somehow commanding a rise and neither ECU nor driver pack is somehow leaking current into the inlet and airspring valve solenoids then the car won't rise anyway, no?

    IF that's the case (I think it is, but what say you?) then I'll go ahead and try my luck with a new driver pack if for no other reason than they fail a LOT more often than the ECU and they don't cost as much... and I don't need to go asking weird Blackbox for a new code for my Faultmate for the new ECU and ask them for yet another one if it turns out my current ECU is fine.

    Good! Progress! Thanks guys!

    .... or *sigh*... should I take a voltmeter to the driver pack- valve block connector and see if there's any voltage across pins 1, 2, 3, 4, 5 and 10 and 11 when the car is (a) at normal height; and (2) switched off with battery connected; and 3 while there's power coming in through pins 12 and 13?

    I wouldn't even know how to tap the wires without damaging them... unless I can do it with the connector disconnected and tap the pins directly without prompting the ECU into commanding something that will change the results of the test.... or hard faulting it entirely.

    Yeesh!
     
    Last edited: Jan 16, 2021
  5. brianp38dse

    brianp38dse Well-Known Member

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    I thought the suspension ecu was under the left hand seat was plug and play no codeing needed.
     
  6. DarthDude

    DarthDude Well-Known Member

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    I don't think @wammers is talking about coding. It's possible that the ECU is sending 12v to the inlet and airspring solenoids when it shouldn't do, causing the car to rise. The other possibility is that the rogue current is being fed by the driver pack to the solenoids, but we do agree that given the problem occurs when the battery is present, but doesn't when it's not, that the issue most likely lies with either the driver pack or the ECU.

    Oh wait- you mean me with the codes.... yes... the big problem with the Blackbox Solutions Faultmate is that it is ECU-specific in that it'll only work on MY ECU. If I swap another one in there, it won't work until Blackbox allows it to, with some codes they'll email me if (a) I request it; and (b) they're around to generate the codes in the first place.

    ... and if it turns out that my old ECU is fine then I'll need Blackbox to send me another set of codes so that the Faultmate will work with my ECU again.

    This is the main reason I advise people to not buy the Faultmate system unless they really have to.
     
  7. brianp38dse

    brianp38dse Well-Known Member

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    My reply was to you mentioning ( and I don't need to go asking weird Blackbox for a new code for my Faultmate for the new ECU)
     
  8. DarthDude

    DarthDude Well-Known Member

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    Yeah... sorry about that. My braincell fired just after I hit "Post Reply". I've edited my post to answer you.
     
  9. backinblack

    backinblack Well-Known Member Full Member

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    I know the L322 only self levels downwards to match the lowest wheel height, I was asking if the P38 when working correctly self leveled upwards, to which the answer is no :)
    I'm learning too:D

    What if you disconnect the power from the valve block or inlet valve but leave the battery connected. But I guess that's only the same as removing the battery.
     
  10. DarthDude

    DarthDude Well-Known Member

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    Yep..... the only way I can think of to test the ECU or the driver pack without actually bunging a replacement in there and see what works..... is to go over the connectors, pin by pin to see which has voltage when it shouldn't, but even that will require some sort of special equipment- at least a male-female pair of connects to go between ECU and driver pack and again between driver pack and valve block with a little bit of the wiring exposed so you can tap the wires while leaving the connection between ECU and driver board, and driver board and valve block intact so that the very act of measuring doesn't leave an open circuit where the ECU isn't expecting one and reacting in a way that'll render the testing null and void.

    Oh well... live and learn. That's what forums like this are for, no?

    As I said earlier I'll start with the driver pack. Mine is over 10 years old now and between it and the ECU, that's the one that's far more likely to have gone.

    Wish me luck, guys!
     
  11. backinblack

    backinblack Well-Known Member Full Member

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    Good luck
     
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  12. Mark Piercy

    Mark Piercy Well-Known Member Full Member

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    Just pull the delay relay with battery connected.
    Then refit the relay and disconnect the driver pack. Perhaps?
     
  13. DarthDude

    DarthDude Well-Known Member

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    Actually that might be a good idea if I can supply power from the delay relay direct to the drive pack, without connecting the ECU to the drive pack. That'll tell me if the rogue current is leaking from the drive pack or commanded by maybe another leak in the ECU.

    Hmmmmmm
     
  14. pwood999

    pwood999 Well-Known Member Full Member

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    As Wammers said earlier, the ECU does not command the car to rise when engine is off. When it wakes up, it checks the relative corner heights, and opens the exhaust & corner valves in an attempt to level the car. This is a waste of air, hence why many people fit an ignition powered disable relay between fusebox and the delay relay. Who cares if it's level when parked !!

    If the Inlet valve is leaky, then when the ECU tries to self-level when parked, it should also open the exhaust valve which will dump any air leaking past the inlet valve out of the exhaust.

    Testing the driver pack & valve block without the ECU is easy:
    • Unplug the connector at front of the valve block.
    • Apply 12V to pins 12+13, plus ground to pins 10+11 (this powers the driver pack)
    • If you apply 12V to each of 1, 2, 3, 4 in turn you should activate the corner valves.
    • Apply 12V to pin 5 for Inlet valve, or pin 6 for exhaust valve.
    • To raise any corner, simply apply 12V to Pin 5 plus any of pins 1-4
    • To drop any corner, simply apply 12V to Pin 6 plus any of pins 1-4
    Do NOT apply 12V directly to the solenoids.
     
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  15. Mark Piercy

    Mark Piercy Well-Known Member Full Member

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    I did the delay relay shutdown for a while and it causes the suspension to go to either full height or access height. I returned it to normal as I didn't want to bugger the ecu or the relay. Tbh, now the system has had all the rubber stuff like rings and bags and so on replaced it..............









    Shhhhhh.........







    It works....
    Love you range rover.. Xxxxx
     
  16. oakey

    oakey Well-Known Member Full Member

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    If I understand solenoids correctly, a leaking current to a solenoid will do nothing until suddenly it has enough and fires so opening the valve fully. I never thought that a wee bit of current would open a solenoid valve a wee bit
     
  17. pwood999

    pwood999 Well-Known Member Full Member

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    It's been posted many times before, but just in case below is how it works in the P38. The signal from ECU to Driver pack is 12V On-Off. There's no "current leakage from ECU" to worry about.

    In theory you could try applying a variable 0V-12V signal to the driver pack input, but all that will do is confirm the switching point (probably 5-7V threshold, but never bothered to check it).

    If the car rises while parked, there's leakage inside the valve block - period.

    upload_2021-1-16_17-34-1.png
     
  18. DarthDude

    DarthDude Well-Known Member

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    Sure- I get that... but SOMETHING is causing the car to rise when it's parked with the battery connected and that something isn't there when the battery's disconnected. The test you describe will test the driver pack for function, sure.... but I know the driver pack works enough to open and close the valves because if it didn't then the entire system would be wonky. It will be useful- if it can be safely done, which I think it can- if I can apply 12v to 12 and 13 and earth 10 and 11 on C152 and then go over to C139 and check for voltage between pins 1 & 2, 6 & 10, 8 & 12 and 9 & 13 which will cover the airspring valves and also 7 & 11 for the inlet valve. That should at least tell me if there's current going to the airspring and inlet solenoids when all the driver pack is receiving is 12v power and no signal from the ECU, no?

    What say you?

    Hmmmmm.....
     
  19. DarthDude

    DarthDude Well-Known Member

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    Yes. there's leakage inside the valve block when the battery's connected and no leakage inside the valve block when the battery is disconnected.

    What I'm trying to find is what could possibly cause that.
     
  20. DarthDude

    DarthDude Well-Known Member

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    Well neither did I, to be honest, until I came across this lil situation. What's visibly happening is that car goes up when there's a battery connected, car doesn't go up when there's no battery connected. That's observed fact. The rest is conjecture.
     
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