AL4 wont move on 2nd or 3rd gear

[Sitikkaukko]

Hi,

It’s the infamous AL4 gearbox. 2012 C4 1.6 VTi 120.

The problem is that at least 2nd and 3rd gears won’t engage. In 1st and reverse the car works and moves normally, but when the transmission shifts to 2nd or 3rd (or if I manually slap those gears in), the transmission slips or can’t engage those gears so basically doesn't matter how much gas I give when it's on 2nd or 3rd, the car won't move. The fault started suddenly. The fault codes are P072F (Fault: controlled converter slip) and P0721 (Vehicle speed data fault: consistency).

As I understand it, P072F is caused by the transmission slipping, and P0721 is because the speed is e.g. 0 even though 3rd gear is selected and the engine is at, say, 3000 rpm.

The speed sensor otherwise seems to work OK, because in 1st gear the speed shows correctly in live data, etc.

I’ve tried to monitor the gearbox oil pressures and compare them to the guide pressure, and from the freeze frame for P0721 you can see, for example, that guide pressure is 21 bar, but the gearbox oil pressure is only 11.5 bar.

In P, N, R and 1st gear, guide pressure and oil pressure follow each other, so apparently the E1 circuit should at least be OK.

Pressures for 2nd and 3rd seem a bit difficult to investigate because the transmission behaves like this: when I put it in D, the box first tries to select 3rd gear but it won’t go in, then it tries 2nd and that won’t go in either, and then it stays stuck cycling like that trying to select 3rd. The pressures were: Guide pressure 13.3 bar and Oil pressure 4.2 bar, and “gear engaged”: Refuge (Hydraulic 3rd). But the pressures fluctuate a lot because the box can’t really decide which gear it’s trying to engage…

As far as I know, the solenoids have never been replaced. Can they cause a complete failure to engage 2nd and 3rd? I don’t know about 4th gear because in manual mode it refuses to go that far…

I changed the oil a little over 6 months ago. As far as I know it hadn’t ever been changed before, and before the oil change the box would occasionally go into limp mode, and the fault code then was “Pressure regulation fault.” I read that this can be caused by old oil or solenoids. The oil change helped, and after the change the code didn’t come back and the box didn’t go into limp mode anymore. It wasn’t a full change though (not done by flushing), so apparently some old fluid remains in the torque converter.

I also checked the condition of the oil now—whether there was metal glitter etc. in it—but the oil was clean and didn’t smell burnt, so it may not be a total catastrophe.

[Paul-R]

How many miles has the vehicle done? Has it ever had the gearbox oil changed?

[Sitikkaukko]

Car has 166 000 km, so in miles about 103 000 miles. I changed the gearbox oil about 6 months ago.

[mickthemaverick]

Changing the oil in an AL4 should be done in 3 stages, emptying and filling with new each time and driving a couple of miles between each swap. That will ensure you replace the majority of the old oil. If you literally drained and refilled just once you are probably still running on up to 65% old oil and the new you put in will be badly compromised. Compared to a rebuild it is relatively cheap to carry out the proper job and see how it goes.

[Sitikkaukko]

Okay, thank you. I will try doing a new oil change. I checked the current oil for contamination by taking about 50 ml out and visually inspected it for anything weird. The colour of the oil was like reddish brown so for sure there is old oil mixed with the new. Just speculating a little; if new oil change doesn't help, is there anything ''common'' that could cause the transmission to slip fully on 2nd and 3rd gear? Can faulty solenoids cause that?

[Paul-R]

Does the AL4 gearbox have an ECU that needs 'telling' that there's new oil been fitted?

[ozvtr]

I checked the current oil for contamination by taking about 50 ml out and visually inspected it for anything weird. The colour of the oil was like reddish brown so for sure there is old oil mixed with the new.

Out of the factory the fluid is amber, so the fluid has been changed at some point. The fact that it's brown(ish) indicates that the fluid is worn.

Just speculating a little; if new oil change doesn't help, is there anything ''common'' that could cause the transmission to slip fully on 2nd and 3rd gear? Can faulty solenoids cause that?

No, not the classic main pressure and converter lock modulating solenoids.
You didn't mention reverse or 4th gear. So I'll assume they work.
I would suspect the E2 clutch pack, the actuator seal or the EVS2 electrovalve. The sequence electrovalves (in this case EVS2) are usually fairly reliable, so IMHO it's the E2 clutch pack.
You can try changing the transmission fluid but If that doesn't work, you really need to seek professional help.
Transmission fluid spec is Mobil LT71141.

[ozvtr]

Does the AL4 gearbox have an ECU that needs 'telling' that there's new oil been fitted?

There is an "Oil wear counter" in the ECU to "compensate" for worn oil. When the wear counter gets to a certain number it will flag a fault in the gearbox and tell you the oil needs to be changed.
I call BS on this as:
1) the manufacturer says the gearbox is "sealed for life"! Not true!
2) how does the gearbox ECU "compensate" for worn oil?

IMHO the fluid should be changed "every couple of years" (I don't know how long...there is no spec! Just don't never change the fluid).

[Stickyfinger]

1) the manufacturer says the gearbox is "sealed for life"! = Company Warrantee time limit = "life"

[xantia_v6]

1) the manufacturer says the gearbox is "sealed for life"! = Company Warrantee time limit = "life"

2) "life" = "until it breaks"

[Sitikkaukko]

I checked the current oil for contamination by taking about 50 ml out and visually inspected it for anything weird. The colour of the oil was like reddish brown so for sure there is old oil mixed with the new.

Out of the factory the fluid is amber, so the fluid has been changed at some point. The fact that it's brown(ish) indicates that the fluid is worn.

Just speculating a little; if new oil change doesn't help, is there anything ''common'' that could cause the transmission to slip fully on 2nd and 3rd gear? Can faulty solenoids cause that?

No, not the classic main pressure and converter lock modulating solenoids.
You didn't mention reverse or 4th gear. So I'll assume they work.
I would suspect the E2 clutch pack, the actuator seal or the EVS2 electrovalve. The sequence electrovalves (in this case EVS2) are usually fairly reliable, so IMHO it's the E2 clutch pack.
You can try changing the transmission fluid but If that doesn't work, you really need to seek professional help.
Transmission fluid spec is Mobil LT71141.

Reverse is working normally like 1st gear. I don't know about 4th because the gearbox doesn't want to even try to shift to that even in manual mode. I of course cannot get much speed to try it while driving because of just 1st gear working forward. I found a forum post (which is in russian) that a guy had exactly the same symptoms (same DTC's and only 1st and Reverse gears working, other gears fully slipping/not engaging). This guy had some kind of stopper or something which had detached and was blocking the piston which pushed the E2 clutch pack. I guess mine could be the exact same or something else similar. I will be taking the transmission out of the car and will disassemble it in the near future to find the exact cause and possibly repairing it.

[Sitikkaukko]

Question related to this. I have choosen to just replace the transmission with a working one. I'm just wondering if I can put AL4 from a different car to this? Current one is with code 20TS67 (according to part catalog).
Can I replace it with AL4 with code 20TS28 or 20TS29? In the box it has part number 9659488480.

[xantia_v6]

You need to be careful, as there are several variants of the transmission and some won't work well, and others wont work at all.

Transmissions from petrol engine and diesel engines should not be swapped, as they have different characteristics and may shift roughly. Transmissions from different models of car or engines with different capacity may have different gear ratios which will cause the transmission ECU to go into limp mode while driving.

[Sitikkaukko]

If I take AL4 from DS3 with the same engine (1.6 Vti 120) even though the transmission ''type'' is different in the donor car (TS28) but the ratio is same 20x73 and mine is TS67 with same 20x73. It should be ok? Of course I will be using my old TCU.

[MattBLancs]

I wonder if you've had the same mechanical failure (all be it on a different band - it was first gear mine lost) as my 406 Coupe's AL4?

I'll see if I can find a picture