Peugeot 308 AL4 Gearbox no power P0721

Nav,
You're not at the point of deciding if you want to keep the 308 or pursue further as this AL4 could be toast or the solenoids just need replacing or the whole valve body. If you attempt these yourself with the right tools it will save you big $$$ and can be done with box in the car.

And these may still not fix the issue which means a box out rebuild or swap with a known working AL4.

I've been through this chasing my tail and had the AL4 out 1/2 dozen times and the only fix was swapping out the box including torque convertor so even after rebuilding the AL4 and reinstalling we never worked out why it wouldn't move the car. I threw this rebuilt AL4 away so nobody else had to deal with it.
 
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Hi
I have now cleaned the valve body when it was opened a bolt from the valve body was stuck to the magnet. Anyway
the car is still not picking up properly in 1st and looks to be going into 3rd gear as a safety feature (see pdf from Autel Maxisys scan)

My question is the pressure difference that the ECU expects (guide pressure) and the actual pressure has great difference in value. Is this an issue, and so would it be the pressure regulation solenoid at fault? I don't get any actual error for any solenoids.

Also when I scan the car the P0721 error freeze data shows pressure difference too see snapshot
 

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Hi
I have now cleaned the valve body when it was opened a bolt from the valve body was stuck to the magnet. Anyway
the car is still not picking up and looks to be going into 3rd gear as a safety feature (see pdf from Autel Maxisys scan)

My question is the pressure difference that the ECU expects (guide pressure) and the actual pressure has great difference in value. Is this an issue, and so would it be the pressure regulation solenoid at fault? I don't get any actual error for any solenoids.

Also when I scan the car the P0721 error freeze data shows pressure difference too see snapshot
 

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Wow. Are you saying you found a loose bolt inside the valve body? Is it possible this bolt is not just an 'extra' but it belongs somewhere?

Cheers

Justin
 
Yes the bolt belonged to the valve body not extra. I put it back and tightened it up. Amazing that a car with so less mileage 27k could have a loose bolt, and it came undone completely.
 
Would say someone's been in there before for a loose screw to have dropped out completely.
Are all 4 gears showing the same low pressure?
 
You may also have dirty contacts in the transmission control switch (on top of the gearbox). This is a PC board with tracks and wiper arms, so the grease goes gummy and gives intermittent contact problems. It talks grey code to the gearbox ECU and if it transmits with a dirty wiper arm (7 of) the computer gives either a communication error or no error at all. Post in tech section as to how to deal with it. Check also for degraded insulation in the transmission wiring loom under the left end of the gearbox where it runs inside a sleeve. The insulation on some batches of wires could crumble allowing the wires to contact each other. If you want to get dirty, this will do it for you...
 
You may also have dirty contacts in the transmission control switch (on top of the gearbox). This is a PC board with tracks and wiper arms, so the grease goes gummy and gives intermittent contact problems. It talks grey code to the gearbox ECU and if it transmits with a dirty wiper arm (7 of) the computer gives either a communication error or no error at all. Post in tech section as to how to deal with it. Check also for degraded insulation in the transmission wiring loom under the left end of the gearbox where it runs inside a sleeve. The insulation on some batches of wires could crumble allowing the wires to contact each other. If you want to get dirty, this will do it for you...
I have changed the neutral switch/multi switch on top of the gearbox. I will check wiring thanks
 
Would say someone's been in there before for a loose screw to have dropped out completely.
Are all 4 gears showing the same low pressure?
Hi dimistyle I have tested to find what is causing this error and found the following :

If I take out the 12 pin connector for the valve body solenoids the car moves forward and is in 1st.
When I place the wiring back then the problem occurs back which is high revs and no movement in 1st (P0721 speed data fault)

Can anyone explain?
 
Hi dimistyle I have tested to find what is causing this error and found the following :

If I take out the 12 pin connector for the valve body solenoids the car moves forward and is in 1st.
When I place the wiring back then the problem occurs back which is high revs and no movement in 1st (P0721 speed data fault)

Can anyone explain?
Jeepers so ECU does not need to be connect to AL4 to actually work!!

Did you take it for a drive or just wheels rotating in the air?

Check if there is a speed sensor installed on the rear of the box, engine side white circular sensor with a metal cover to protect it. Not sure if the 308 uses this sensor or from other location?
 
Jeepers so ECU does not need to be connect to AL4 to actually work!!

Did you take it for a drive or just wheels rotating in the air?

Check if there is a speed sensor installed on the rear of the box, engine side white circular sensor with a metal cover to protect it. Not sure if the 308 uses this sensor or from other location?
The transmission ECU connects to the solenoids in the transmission valve body. This connector is shown in the pic below. I removed the yellow connector and my car worked fine in first gear (Yes, gear worked in AL4 without the ECU intervention). This makes it likely that the fault is within the wiring harness or the solenoids, as technically with no power the solenoids are off and the wiring is not active. I did swap the Transmission ECU awhile back but had the same fault (P0721 Speed data fault with no power to move off in 1st gear). I have no speed sensor on the rear of the box as there is a blanking plate. It uses the abs to derive speed. Once fixed completely, I will summarize on the solution.
 

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Hi this week I have bought a 2nd hand Gearbox 20TS30.
Transferred the valve body with solenoids and the solenoid wiring harness into my existing Gearbox and cleared faults. The result was the same P0721 Vehicle Speed data fault accompanied by flashing snowflake etc and Gearbox faulty.

Next stage would be to replace my existing Automatic gearbox with the one bought. Does anyone have any other suggestions before I go extreme?

Also, I have never changed an automatic Gearbox, is it straightforward? Do I need to look out for anything like positioning the flywheel with auto box in a certain way etc.? I have experience on manual gearboxes. Thanks again
 
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Hi this week I have bought a 2nd hand Gearbox 20TS30.
Transferred the valve body with solenoids and the solenoid wiring harness into my existing Gearbox and cleared faults. The result was the same P0721 Vehicle Speed data fault accompanied by flashing snowflake etc and Gearbox faulty.

Next stage would be to replace my existing Automatic gearbox with the one bought. Does anyone have any other suggestions before I go extreme?

Also, I have never changed an automatic Gearbox, is it straightforward? Do I need to look out for anything like positioning the flywheel with auto box in a certain way etc.? I have experience on manual gearboxes. Thanks again
Its easier than a manual swap. Driveshafts come off without fluid needing to be drained. The crank position sensor ring is on the drive plate that stays on the engine, and the torque converter is attached with only 3 nuts - access these through the starter motor hole after you remove the starter. Torque converter stays with the box as you remove it.

It is bigger though, so where you might get a manual out with the subframe in place, the auto might require it to be removed.
 
Its easier than a manual swap. Driveshafts come off without fluid needing to be drained. The crank position sensor ring is on the drive plate that stays on the engine, and the torque converter is attached with only 3 nuts - access these through the starter motor hole after you remove the starter. Torque converter stays with the box as you remove it.

It is bigger though, so where you might get a manual out with the subframe in place, the auto might require it to be removed.
Hi Haakom,

thank you so much for the information. You say I need to access 3 nuts through the starter motor. I am assuming the crank needs to be turned to access each of the 3 nuts and gear should be neutral? The 3 nuts are attaching the torque converter to the autobox so are the 3 nuts undoing the autobox from the flywheel? Do you have any pic for the nuts?
 
Yes 3 nuts on flywheel side reach is from starter location once removed and auto to be left in neutral. Don't strip the nuts as they are a non standard size thread 9mm x 1mm. I don't recall if 12 or 13mm socket is required.
Subframe out will save you plenty of time.

My concern is you have the snowflake symbol which means the oil change is required and this also needs to be reset in the Auto ECU otherwise it will override any of the standard driving settings.

I have a Haynes manual with all the torque settings I can scan if you haven't found these online
Good luck
 
Yes 3 nuts on flywheel side reach is from starter location once removed and auto to be left in neutral. Don't strip the nuts as they are a non standard size thread 9mm x 1mm. I don't recall if 12 or 13mm socket is required.
Subframe out will save you plenty of time.

My concern is you have the snowflake symbol which means the oil change is required and this also needs to be reset in the Auto ECU otherwise it will override any of the standard driving settings.

I have a Haynes manual with all the torque settings I can scan if you haven't found these online
Good luck
Hi thank you for the information. I managed to win a 308 Haynes manual on eb** today so should be able to look up the settings. Planning to execute the Gearbox change once this is received.
 
Yes 3 nuts on flywheel side reach is from starter location once removed and auto to be left in neutral. Don't strip the nuts as they are a non standard size thread 9mm x 1mm. I don't recall if 12 or 13mm socket is required.
Subframe out will save you plenty of time.

My concern is you have the snowflake symbol which means the oil change is required and this also needs to be reset in the Auto ECU otherwise it will override any of the standard driving settings.

I have a Haynes manual with all the torque settings I can scan if you haven't found these online
Good luck
Hi Dimistyle,

any chance I can get those Haynes manual torque settings ? It is a 3 day holiday break here in the UK and my Haynes manual will not arrive till later this week. I am trying to complete the car earlier and would like to take advantage of the 3 day break. Thanks for your help.
 
Hi Dimistyle,

I have installed the replacement gearbox, but it has a small problem of its own which is with normal cable holder bracket it fails to go from Drive back to neutral as rubber bushes give it a bit of play. I have to move to park or reverse and then to neutral. If I remove the bushes, then it stiffens the bracket and the gears engage well. I should not have to remove the rubber bushes, as these are part of the original gearbox fitting. I need to decide whether to return the Gearbox or keep it.

The problem of P0721 and the car not moving or having no power has gone away since the replacement gearbox has been fitted. The car moves!!!!!!!!!!!!!!!!!!!! No Error P0721 on the scanner

Now for additional investigation on my existing 27K auto Gearbox 20TS30 I opened it up and the filter did not look too bad so cleaned it up. I looked further to remove the filter and found the following broken See broken Band F3. This is likely to be the issue with P0721 and my original gearbox having no power. I hope this helps someone, as my investigation into P0721 speed data fault has been thorough.
 

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Hi Dimistyle,

I have installed the replacement gearbox, but it has a small problem of its own which is with normal cable holder bracket it fails to go from Drive back to neutral as rubber bushes give it a bit of play. I have to move to park or reverse and then to neutral. If I remove the bushes, then it stiffens the bracket and the gears engage well. I should not have to remove the rubber bushes, as these are part of the original gearbox fitting. I need to decide whether to return the Gearbox or keep it.

The problem of P0721 and the car not moving or having no power has gone away since the replacement gearbox has been fitted. The car moves!!!!!!!!!!!!!!!!!!!! No Error P0721 on the scanner

Now for additional investigation on my existing 27K auto Gearbox 20TS30 I opened it up and the filter did not look too bad so cleaned it up. I looked further and found the following broken See broken Band F3. This is likely to be the issue with P0721 and my original gearbox having no power. I hope this helps someone, as my investigation into P0721 has been thorough.
Yep that brake band is you're culprit and as you have worked out by spitting the case there is no way to replace it while box is in the car.

So fork out for a new replacement and reinstall or get the cable connected properly on the replacement is up to you.

You can always have a spare AL4 i know i did for a few years.

The gear cable should be clipped into the bracket there's a little lock/locator on the blue circular piece on the cable.

Setting the neutral switch will be your problem.
You are supposed to connect your multimeter across the 2 pins and rotate the lever until you get an open circuit but it never worked for me. I just check the dash displays neutral and tighten the 2 bolts. Takes a few attempts and stops the wiggling of the lever to put into neutral.

Good news car is moving again
 
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