4HP20 2.2 C5

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cachaciero
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Post by cachaciero »

Sid_the_Squid wrote:Have you tried a more manual solution of changing the box oil? That certainly wears out.
Agreed the oil does get old and really does need changing BUT this is not a mechanical problem, mechanically the box works fine (hastily touches wood, rabbits paw and other objects believed to keep evil at bay :-)
Yhe fact that it changes correctly using the Tiptronic manual mode or In auto with Cruise control engaged proves that the problem is the brain box i.e ECU OR something that talks to the ECU.

cachaciero
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Post by Sid_the_Squid »

I see where your coming from but all the same I'd change it, a oil change certianly will not make things any worse could even solve the problem. I base that last statement on nothing more than new oil will just make everything run a little nicer. So far I've had the GG for just over a year, changed the box oil for a 4th time on friday, each time the gear change get smoother, theres nothing 'wrong' with the box to begin with, but its certainly better now.
Gone to the dark side.

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Post by cachaciero »

Well another straw to clutch at:
Suspension is another area where I have some problems while checking ride heights I discovered that the rear wheels differ in diameter by 4cm. Now the two tyres are from different manufacturers but are the correct nominal sizes, the amount of wear on both is similar, I have to say I was surprised at what is quite a large difference.

Now according to the documents that I have the Auto Box uses Left and Right rear wheel speeds for "quote" To select the changing law and
calculate the gear Wheel speed processing.
Now with such a difference in diameters there must be quite a difference in wheel speed Left to Right wonder what the autobox makes of that. Looks like another day with the Lexia to see what the differences are :-)

cachaciero
2006 Toyota Prius T Spirit
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Post by cachaciero »

Well checked the rear wheel speeds the difference between the two is 1-2KM / hour at 50 Kmh so that's 2-4% difference I'm not convinced that that would make a lot of difference to anything :-(.

Have configured the BOX for a non-ESP car working on the theory that then the box won't look at data from the ESP ECU which would include rear wheel speeds,- didn't seem to make any difference.:-(

Had the ECU open yesterday hoping to see something like an obvious J Tag interface but no. Mind the connector to the box has 88 pins and only about fourteen are used so there's a lot of scope for other functionality but without circuit diagrams and more info which I am sure Bosch wouldn't release even if I could find someone to talk to there is little chance of discovering more.

cachaciero
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Post by cachaciero »

Update:-

Well after several more days of monitoring and research I am little further forward to finding a resolution to this problem.
As a technical reference I have the 4HP20 training manual for the Xantia widely available on the Web plus another Training document which discusses in vague detail the interfaces on the C5.

I am assuming that in general terms the box and ECU work much as the Xantia.

From this, with a cold box the Xantia implementation directly selects a MAP SK2 close to the economy end of the scale i.e it apparently by-passes the autoadaptive logic.
The C5 does this too for the first couple of miles or so from cold the box performs largely as one would expect and gear changes can be initiated by appropriate use of the throttle even into 4th at relatively low speeds and trailing throttle. However once the box has warmed up all this goes out of the window.

According to the info I have cruise control has it's own map, this is logical in that in cruise there is no requirement for the box to match a driving style so no requirement for autoadaptive logic.
In cruise control the box works correctly although it also appears to respond to "sport" mode in cruise which shifts the change points up a bit so that might imply that there are actually two maps for cruise but one thing is for sure the Auto-adaptive logic is by-passed.

Driving the box in normal auto mode with and without "sport" mode engaged appears to be little different.

It seems to me from all of this that the problem I have is within the ECU and specifically the autoadaptive bit which seems to have got itself "locked" into the high end of the sport mode MAP range.

The only possible course of action I can see is to either get another ECU and see if that is by chance different or find a way of re-flashing the one I have. Any suggestions as to outfits that may know how to do this would be welcome.

Now to cap it all the speedo has failed, yet another common failure at around a 100K like I said at a 100K these things are end of life it is just one thing after another and I am getting mightily p?*sed off.

cachaciero
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Post by cachaciero »

Well the problem still exists, had occasion to visit my local Citroen Franchise yesterday to buy some odds and sods.
Got talking to their workshop manager, basically my pitch was that I was prepared to let them have the car to carry out a re-flash of the gearbox ECU, this caused a bit of head scratching and then he got his auto gearbox expert who I have to say did appear to be knowledgeable. Any way after much discussion they agreed that it was a very weird problem, maybe, logically it was the ECU and no they couldn't re-flash ECU either unless there was a more up to date load which there isn't. They told me that if during the downloading to an ECU there was a glitch the downloading procedure couldn't be re-started and the ECU would be scrap.................
This latter bit I accept that they believe it to be the truth because Citroen havn't told them any different but I don't believe it is the case....if you have the gear and knowledge. What is really needed is something like a Galletto that can read and download the mapping files to a computer

Anyway the bottom line is that this appears to be beyond the resources of a main dealer to resolve short of changing the ECU for a new one (Mega bucks).

I guess that the next step is to find another ECU that I can "play with" although there is one other outfit I want to talk to first.

Coming back to suspicions as regards external sensors the steering sensor has an input indirectly via the ESP system. I had a closer look at this the other night. I have to say that if you plot the output from the steering angle parameter on the calibration pages it gives some weird numbers. Basically a tad to the left and the O/P is -127 and a tad to the right O/P +52. There is nothing in between no hysteresis there is no precise value which can be said to be straight ahead, straight ahead can be either of those two values at the moment I am undecided if this is right or wrong on balance I have to assume it's right as nothing else complains but...


cachaciero
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1995 XM 2.1 TD Auto SX died @ 140K
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Post by cachaciero »

Well time has gone by and it's time for an update.
basically revisited some things, principally re-programming as it it's called on the lexia which really means re-configuring the load that the box has.
The gearbox software apparently knows about several engine configs, three of them have the 2.2 included. In addition it is possible for each of these configs to have such minor tweaks as town mode enabled (which I believe is another mapping) but more interestingly whether the car has ESC (P) or not.

I have tried all three configs, the first got me really worried having put it in couldn't select a gear, lever latched and auto-box failure warnings, cold sweats and sphincter muscle working overtime :-)
Fortunately the second option which was the one I had started out with put everything right.
Finaly tried the third option with no ESC, having put this in the ESP/AS warning came up. Shut everything down and switched ignition on no warnings.
Drove the car auto-box now works as I would expect it to changes gear in a sensible fashion and no longer hangs on to second.

So in a nutshell telling the auto box ECU that it doesn't have an ESP system fitted makes it work correctly, ergo the ESP system when enabled is telling the gearbox to hang on to lower gears but why?? which paramater bit of data exactly could cause that?

cachaciero
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Post by jimleshed »

Doesn't the ESP also include the yaw sensor...IE its sensitive to the cars angle, climbing, dropping or sideways. I think thats the bit that causes it to drop a gear when going down a steep hill. I guess it would also include holding gears if climbing a hill. I wonder if its either moved or loose or duff, causing odd signals. I think in our car (2.2 HDI Excl) it lives under the cubby hole behind the handbrake.
I'm just clutching at a straw for you.....
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Post by cachaciero »

Yes the ESP bit does has a YAW sensor but this is to detect horizontal movement around the vertical axis i.e incipient spin i.e hanging the tail out, did go through an exercise of re-initialising this it being on the Lexia menu but with little difference. it is an interesting thought though, as this holding onto second often appears to happen after going around a bend. Now I know that the box has a mechanism to prevent changing gear while going around a bend and it was my understanding that this came from the steering wheel sensor but it would make sense to prevent gear changing if the car had started to spin. It does appear that with ESP inputs disabled into the box that steering wheel angle still inhibits gearchanges when going around bends.
Must set up the lexia and go for a drive monitoring the dynamic values of of the ESC system, might try resetting the ESC sensor again this time on a level surface.

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Post by CitroJim »

Gosh, this is getting interesting cachaciero :D

I'm sitting here amazed at how they've extended the basic functionality of the 4HP20 since it made it's debut in the V6 Xantia!!!

Pleased you're starting to get to the root of this...
Jim

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Post by dnsey »

Presumably, the ESP uses the ABS pulses to determine wheel rotation. Now if, as you've said, the rear wheel sizes differ, I'd expect it to become confused, especially when changing up or reducing power doesn't correct the 'wheelspin'. It must be worth substituting the odd-sized wheel with the spare to see if it makes a difference.
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Post by lexi »

It is kind of fascinating. Tell me Cach. Why did you buy/keep this thing?

You gonna turn it into a Xmas high level puter game ? :shock:

I'm just making a note here and it says.."2.2 NEVER buy one " there!.....written on my forehead :lol: :lol:
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Post by CitroJim »

lexi wrote: I'm just making a note here and it says.."2.2 NEVER buy one " there!.....written on my forehead :lol: :lol:
I've something similar written...

"Stick with a Xantia for as long as possible!"

Mine only ever holds on to gears when stone cold or the Sport button is depressed :D
Jim

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Post by cachaciero »

lexi wrote:It is kind of fascinating. Tell me Cach. Why did you buy/keep this thing?

You gonna turn it into a Xmas high level puter game ? :shock:

I'm just making a note here and it says.."2.2 NEVER buy one " there!.....written on my forehead :lol: :lol:
Why did I buy it? seemed like a good idea at the time :-)
Why do I keep it? good question one I keep asking myself :-) it's the challenge I suppose, there are I know at least four people with this problem and I suspect many others if they can't find a solution / or at least an explanation I will, I refuse to be beaten by a heap of French Merde :-)

cachaciero
2006 Toyota Prius T Spirit
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1995 XM 2.1 TD Auto SX died @ 140K
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Post by cachaciero »

dnsey wrote:Presumably, the ESP uses the ABS pulses to determine wheel rotation. Now if, as you've said, the rear wheel sizes differ, I'd expect it to become confused, especially when changing up or reducing power doesn't correct the 'wheelspin'. It must be worth substituting the odd-sized wheel with the spare to see if it makes a difference.
The ESP does I believe use the ABS pulses to monitor individual wheel speeds these are also used to give car speed to the speedo. If you program the ESP ECU for a manual box as opposed to an auto the speedo will stop working.
Yes not really sure about the difference in wheel size it was as I remember only a small percentage difference I wasn't really convinced that it would make a difference, but now I have new tyres I suppose I ought to put it back to standard and see if there's any change.

cachaciero
2006 Toyota Prius T Spirit
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1996 XM 2.1 TD Auto VSX
1995 XM 2.1 TD Auto SX died @ 140K
1987 CX 2.5 Gti Turbo II dead
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