Aisin AM6 problem

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barbrady
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Aisin AM6 problem

Post by barbrady »

When I go on a motorway for hundreds km's, my transmission do the following. Usually I go with 140 km/h, and when I need slow down a bit (to 100-110) and after speed up again the gear shifted back to gear 5 and stuck there. I am going with 140 km/h in gear 5. At this time the manual change option also cease. I pull the shifter to manual, but the letter D not disappear next to the 5 on the instrument panel, and do nothing if I pull back or push forward the shifter. If I slow down to zero, and wait some seconds, everything working well again for hundred km's. The last gear shift oil change was 33k km ago. Does anyone have any idea what the reason is?
Last edited by barbrady on 20 Aug 2018, 08:12, edited 1 time in total.
Mattschmidt
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Re: Aisin AM6 problem

Post by Mattschmidt »

Looks like a solenoid problem. And never under no circumstances meddle between manual and D modes without stopping the car.
barbrady
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Re: Aisin AM6 problem

Post by barbrady »

Mattschmidt wrote: 19 Aug 2018, 20:28 And never under no circumstances meddle between manual and D modes without stopping the car.

How do you mean this?
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Re: Aisin AM6 problem

Post by Mattschmidt »

Want a modr change stop the car and select the mode. You'd be better off.
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Re: Aisin AM6 problem

Post by barbrady »

Mattschmidt wrote: 19 Aug 2018, 21:01 Want a modr change stop the car and select the mode. You'd be better off.

This is in the original Citroen Manual:

"The change from position D (driv-
ing in automatic mode) to posi-
tion M (driving in sequential mode)
or vice versa can be made at any
time.
The gear selected is displayed on
the instrument panel."
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Re: Aisin AM6 problem

Post by Mattschmidt »

Right. Can be just my prejudice. If the manual says so then it must be true. Sorry my bad.

But the solenoids need chcecking, a.k.a electrovalves. Try that.
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Re: Aisin AM6 problem

Post by xantia_v6 »

I think that a better first step would be to connect the car to a Diagbox computer and read the fault codes for the transmission.

Are the gear changes all correct and smooth when the transmission is not displaying the symptoms described above?
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Re: Aisin AM6 problem

Post by barbrady »

No fault code. Exept this, no any problem with the transmission I have red about the automatic transmission problems on the internet, but mine is working properly. That's why I don't understand this issue. It seems the ecu is "confused" and "think" the transmission is in one higher gear at that moment. When this problem consist, and I slow down to stop, the changing backs are earlier than normally. The RPM is higher than a normal slow down. I hope I am understandable :)
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Re: Aisin AM6 problem

Post by Gibbo2286 »

Mine tends occasionally to hold in too low a gear after descending a hill, (took a long time to change up) I found that switching off the ESP made a difference but I've only just tried that, wondering if it's an ESP sensor problem.

Did I read somewhere also something about dodgy brake pedal switches?

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Re: Aisin AM6 problem

Post by moizeau »

Mattschmidt wrote: 19 Aug 2018, 21:01 Want a modr change stop the car and select the mode. You'd be better off.


Certainly is the case with a vehicle with diff lock, when unlocking, or a series Landy when using Hi and Lo range or coming out of 4wd in high range because this involves going into Lo and then back to Hi, but as already mentioned the AM6 is slightly more refined and civilised (and technical)
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Re: Aisin AM6 problem

Post by EDC5 »

I'm not sure what could be the issue with your AM6. With mine, I find that the gearbox holds onto lower gears when the engine is cold (most notably holding onto 3rd gear at 30mph, only changing to 4th at 32 or 33) It also holds a lower gear when descending a hill but this for the purpose of engine braking.

Has the oil ever been changed on your gearbox?

I think the best option would be to see if there are any faults on the AM6 ECU (which can only be read with Diagbox).

Can you change gear manually when driving at slower speeds?
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Re: Aisin AM6 problem

Post by white exec »

I remember auto 'boxes (eg BW65) in the '70s doing just that; cold fluid struggling to get through tiny orifices! Delayed changes, executed with a s-l-u-r-r. Different now, of course, with digital fluids. :-**
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Re: Aisin AM6 problem

Post by Sloppysod »

What. Wheels/tyres does you car have. It maybe that the car does not know exactly what speed you are doing. I had similar issue with gearbox not changing up pulling out from bend or out from a roundabout. It turned out, one of the rear wheels had a different rolling diameter than the others!! Not sure of the maximum difference, but put a tape measure around your tyres and check they are the same(ish).

Added - I took both of my rear wheels off and the circumference was 15mm different , which means the diameter was about 2.4 mm larger on one wheel.
Last edited by Sloppysod on 21 Aug 2018, 19:11, edited 1 time in total.
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Re: Aisin AM6 problem

Post by xantia_v6 »

I think that this issue might be related to the ECU detecting that the transmission is overheating, and moving it to a mode where less heat is generated.

If you can arrange to have a diagbox connected when the fault is likely to happen, and record live data of interesting transmission parameters, I would hope that you get closer to identifying the cause of the problem.
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Re: Aisin AM6 problem

Post by Gibbo2286 »

xantia_v6 wrote: 21 Aug 2018, 06:45 I think that this issue might be related to the ECU detecting that the transmission is overheating, and moving it to a mode where less heat is generated.

If you can arrange to have a diagbox connected when the fault is likely to happen, and record live data of interesting transmission parameters, I would hope that you get closer to identifying the cause of the problem.



Mine, as I said seems to hold a lower gear too long after descending a hill, does the engine braking fine but takes too long to change up afterwards......not all the time though just occasionally. I can live with it. :)

I've never managed to get my Diagbox working but the other tool I bought (WOW Snooper) does check the gearbox and shows no faults.
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