September 02, 2009

AL4 Automatic Transmission - Pressure Regulation Fault

I used to have a problem with my earlier Peugeot [not 308] AL4-Transmission. It was under warranty, so it didn't incur any direct cost to me except time, fuel and toll. But I learned quite a lot in return at no cost for consultation. I just want to share my own experience on the symptoms so that everyone will take immediate action before it is too late and start to make lots of noise in the AutoForum...

Symptoms
Flashing of the "Snow" or/and "Sports" light then the transmission went into the downgraded mode. In this mode the transmission was locked in third gear to enable to continue the operation of the vehicle following by a loss of power. The downgraded mode sometimes preceded by some very harsh [jerking] shifts. However after stopping and restarting the engine, the transmission would usually return to normal operation.

Most of the time the problem appears at unpredictable intervals. Some incidences were on a daily basis, sometimes may have weeks of trouble free operation between incidents.

What was logged in the ECU?
At SC I was told the following fault code was logged in the transmission ECU: "Intermittent fault. Pressure regulation fault, recommendation/variation"

Cause
Being a technical person I usually ask for the explanation. I was told the pressure regulation fault code was triggered when the ECU senses a difference between the calculated pressure and the actual line pressure in the transmission. The pressure difference was caused by internal leakage. Internal leaks could be caused by mechanical wear, a leak between valve body and transmission casing, incorrect adjustment of the manual valve index spring.

The most common cause however is the pressure regulation solenoid valve.

Diagnosis
The diagnosis was not straightforward, several operations were required to eliminate possibilities.

  1. Transmission fluid
    1. ATF level was checked in the transmission. [Note: Low or high fluid levels are equally harmful]
    2. ATF was placed in a clean container for examination.

    The transmission didn't need to be overhauled or replaced because the fluid sample was normal like fresh ATF, i.e transparent. Fluid drained from a transmission that has been in operation for some time is usually dark in colour and lacks transparency, this is acceptable and not necessarily an indication of an internal fault. Caution was exercised with the fluid assessment.

  2. Pressure sensor
    1. With help of the diagnostic computer the transmission line pressure was checked.
      The following parameters were observed.
      At idle in N around 2.6 bars.
      At idle in D around 3 bars.
      Under full load 2200 rpm: 11.5 bars.
    2. Since there was change in pressures, no need to test the sensor and sensor supply.

    Note: A faulty sensor maintain constant pressure of 6,5 bars. This would also mean that the transmission would be in Limp Home Mode and that the fault is permanent. Since the problem usually was intermittent the pressure readings would check out OK most of the time. Since no other problems have been found so far, diagnose continued...

  3. Solenoid Valves
    1. Pressure regulation valve and the converter lock-up valves were replaced.
    2. 2 seals behind the valve body are correctly fitted. The seals were not replaced.
    3. After fitting the valve body, the selector index spring was adjusted
    4. The multi-function switch was also adjusted.
    5. Before fitting the pan , the 2 magnets presence was assured.
    6. ATF was refilled and adjusted the level.
    7. The transmission ECU software was updated for the new solenoid valve because the older software versions are not compatible with the new Borg Warner valves.

    The operations outlined obove resolved the pressure regulation problem.

    If the problem couldn't be resolved Valve-body probably need to be replaced. Worse case, the whole Transmission required overhaul or replacement.


Important reminders to observe
  1. Only use genuine Peugeot ATF.
  2. The fluid level must be correct.
  3. The correct adjustment of the manual valve index spring is very important.
  4. Adjust the multi-function switch after the valve adjustment.
  5. Cleanliness is absolutely essential when working on the transmission.

Is is good to know...


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14 comments:

azhelmy said...

This a very sensitive gear box, hope it will last long before anything happen to my 308...

uncle.D [AHW] said...

For normal use AL4 is maintenance free. Doesn't even need ATF change. Just topup when required. But watch up for the warning lights. If "Snow" or/and "S" start to blink immediately send the car for AL4 diagnosis in no time.

kayeso said...

Cant find dipstick. How to check the level?

AHW said...

Unfortunately there is no dipstick for the AL4 automatic transmission, and the level checking procedure is very complicated.

kayeso said...

I hv checked citroen al4 link, seems like it almost identical to estima acr50. It uses standpipe to prevent overfill right? The only extra work is to remove engine lower cover.

AHW said...

Pls follow this link for AL4 document if you like to read in depth...

http://www.kit-group.ru/sections/AL4%20Transmission.pdf

Andrew Yep said...

Would like to ask for some advice. My AL4 gearbox for my 308 vti is having problem again, for the 2nd time.

The first time, the SC centre says it was the Solenoid Valve, so they changed it. The thing is I saw in the receipt it says it's a 206/207 solenoid valve. Does 206, 207 and 308 share the same Solenoid Valve?

And it has been less than a year, and I am having the same problem again. What a fuss? I am going to send my car to SC soon again.

One more question, is it normal that the gearbox has sound like a lock/unlock clack when stepping on the brake in P mode (gear)??

Andrew Yep said...

Would like to ask for some advice. My AL4 gearbox for my 308 vti is having problem again, for the 2nd time.

The first time, the SC centre says it was the Solenoid Valve, so they changed it. The thing is I saw in the receipt it says it's a 206/207 solenoid valve. Does 206, 207 and 308 share the same Solenoid Valve?

And it has been less than a year, and I am having the same problem again. What a fuss? I am going to send my car to SC soon again.

One more question, is it normal that the gearbox has sound like a lock/unlock clack when stepping on the brake in P mode (gear)??

Andrew Yep said...

Would like to ask for some advice. My AL4 gearbox for my 308 vti is having problem again, for the 2nd time.

The first time, the SC centre says it was the Solenoid Valve, so they changed it. The thing is I saw in the receipt it says it's a 206/207 solenoid valve. Does 206, 207 and 308 share the same Solenoid Valve?

And it has been less than a year, and I am having the same problem again. What a fuss? I am going to send my car to SC soon again.

One more question, is it normal that the gearbox has sound like a lock/unlock clack when stepping on the brake in P mode (gear)??

A.H. Wan said...

Basically all AL4 transmissions are the same but they are improving over time. Hence the transmission ECU and some components found in different cars (and different date of manufacturing) may be different.

Deadey├ę Hunter said...

Oh my days! What a find your blog has been!
I THINK i need to replace the Gearbox Pressure Regulator & Lock Up Solenoid, but i'm REALLY unsure about updating the ECU- i'm reading this is a dealer only kind of thing? Would you divulge how you did it?
Thanks in advance!
Pip Holmes

Anonymous said...

Hi; First of all thanks for the information that you give above. Very helpful.
I have 308 vti and having transmission problem. I've uploaded a video of my car. http://www.youtube.com/watch?v=RGfCZVZwTz8
Can you tell me what is wrong about this one?

Thanks in advance.

Wan Ab.H.A.B said...

Looks like there is a problem with the engine as indicated by the warning icon on the lower left hand side of the instrument panel. Probably your car is running on limp mode - nothing wrong with the transmission. Better send your car for diagnostic test.

rgds

Transmojal said...

Hello, i have a similar problem maybe you could help me. When i start the engine and the lever is in "P" i have 2.65 pressure, i thing this is normal, but when i´m in the road at 2500 rpm the reference pressure is 21 bar and the actual pressure is 1.5 bar. What do you thing about that?. Thanks.

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