C8 2004 AL4 gearbox no oil pressure, tech help please!

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PeteC8
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C8 2004 AL4 gearbox no oil pressure, tech help please!

Post by PeteC8 »

For the last year I have had occasional lockout typically after first 1 or 2 miles, fine once restarted until next cold start. Worsened, finally accompanied by occasional (maybe unrelated) total loss of drive on inclines.
(2004 C8 2.0hdi 90,000 miles)

That was my goad to replace the 2 pressure/lockout valves in the control block.

I stripped and thoroughly cleaned the block, fitted the new valves, and hey presto very low oil pressure. From cold the transmission shifts silky smooth and car pulls fine on flat, and up inclines, not pulling away maybe quite as sharp as it should, but never was very sharp. After a few short loops round the lock, maybe 2 miles, loses drive on inclines and locks out with the standard Auto trans fault alert.

Clues please as to my next step! I am no stranger to the grubby bits and have referenced various texts so have a little idea of the system and need pointers!

Sorry about all the back story, trying to be thorough.

Many thanks!

Pete, frustrated 2004 C8 2.0hdi owner
ozvtr
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Re: C8 2004 AL4 gearbox no oil pressure, tech help please!

Post by ozvtr »

Sounds like the oil pump. However the oil pump is not a "usual suspect" in AL4 failures. AND it would only wear out because of wear particles getting through the filter. Or a blocked filter. That means more trouble in some other part of the gearbox. OR the pump has failed because of external forces or a manufacturing defect.

Could be the main pressure sensor. But if that was indicating under pressure, the ECU would try and compensate and that really doesn't explain the loss of drive.

It's also possible the "new" main pressure regulator solenoid is faulty, I've seen that before. That would explain the low oil pressure AFTER replacing the valve.

A worn manual valve in the valve body? Again, not a usual suspect (unlikely).

My first step would be to replace the new pressure regulator electro valve. After that, IMHO, it's a gearbox tear down or replacement.
PeteC8
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Re: C8 2004 AL4 gearbox no oil pressure, tech help please!

Post by PeteC8 »

Thanks very much for the insight!
One thing that I realise I omitted (severe age related brain fatigue) is that the original pressure solenoids were the 50hz variety, the new ones are 100hz. On reflection, I think maybe amending the ECU parameters should be my first shot!
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Re: C8 2004 AL4 gearbox no oil pressure, tech help please!

Post by Rp0thejester »

Total loss of drive on inclines would suggest MAF issue which I had. Just unplug it and see what happens
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PeteC8
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Re: C8 2004 AL4 gearbox no oil pressure, tech help please!

Post by PeteC8 »

Thanks Ryan, that's a simple one to check. Will try and see!
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Re: C8 2004 AL4 gearbox no oil pressure, tech help please!

Post by Rp0thejester »

It will bring the EML light on but as it's before 2006 it's NOT an MOT failure. My MAF keeps blowing up, replaced several times now. I think the problem is it's intake is by the left wheel underneath. Would be okay if a left hand drive car on the right hand side of the road. But we are right hand drive, driving on the left with the kerb leaves and water/debris being sucked up. I now leave it disconnected and that has solved my acceleration problems, especially uphill
Ryan

'99 Xsara 1.6 X (Red) with Sunkissed bonnet. T59 SBX
'54 Astra Estate 1.7DTI (Artic White)
'06 C8 2.2Hdi Exclusive (Aster Grey)

Champion of Where's CitroJim :-({|=
Yes I ask the stupid questions, because normally it is that simple.
PeteC8
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Re: C8 2004 AL4 gearbox no oil pressure, tech help please!

Post by PeteC8 »

Wow! Just disconnected the MAF sensor, car driving like a sock stuck in the inlet, connected back up and back to " normal" until transmission warms up, then no drive again.

Looking into history, this had the original pressure solenoids, which apparently run on a different frequency to the later ones, needs a Lexia to change the settings.

Trying without luck to find anyone who deals with such cleverness, may end up putting the old ones back in as then at least it was mobile to some extent!
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Re: C8 2004 AL4 gearbox no oil pressure, tech help please!

Post by xantia_v6 »

If you can't find anyone on here with a Lexia, you could try: http://www.blautos.co.uk
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Re: C8 2004 AL4 gearbox no oil pressure, tech help please!

Post by Paul-R »

I think it's not so much having a Lexia, or more properly a Diagbox, but the fact that it will need access to Peugeot's servers. So, either a dealer or someone with paid access to the servers.
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Re: C8 2004 AL4 gearbox no oil pressure, tech help please!

Post by ozvtr »

PeteC8 wrote: 30 Jun 2024, 12:26 Thanks very much for the insight!
One thing that I realise I omitted (severe age related brain fatigue) is that the original pressure solenoids were the 50hz variety, the new ones are 100hz. On reflection, I think maybe amending the ECU parameters should be my first shot!
I don't have access to the ECU firmware revision number (Wheeler does) but revisions after a certain point will run either types of solenoids.
I have a 2003 Citroen C3 that had the old (white connector) solenoids and it runs fine on the new solenoids. Obviously it had a later firmware revision (but it didn't line up with Wheelers', the revision was completely different)). My point is that if your vehicle is from 2004 it's unlikely to have the old revision of firmware and should run fine on the new solenoids.
ozvtr
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Re: C8 2004 AL4 gearbox no oil pressure, tech help please!

Post by ozvtr »

If it is the modulation frequency causing your problems, then as Paul-R says you will need to find someone to update the firmware of the ECU. Either a VERY GOOD auto transmission shop (doubtful), an independent mechanic with access to the PSA network, or a Peugeot or Citroen dealer. This sort of stuff is locked up tighter than a drum.

In the early days of the LEXIA (read: Diagbox) knock-offs, there were some versions of the software that allowed updates to some ECUs' firmware from the supplied CD data. BUT they were only "early" updates...not current updates! Most LEXIA (clone) owners would have updated the LEXIA firmware for better compatibility with their car, but then lost the ability to update ECU's from the CD's. The newer revisions of the LEXIA software retrieves the data from "on line", not Compact Discs. Sorry if that doesn't make sense, but it's the best way that I can explain the situation.

Again, being a 2004 car, I don't think those updates (from the clone LEXIAs) would be any newer than the revision already in the gearbox ECU. That's why you need to get access to the "live" database IF that's the way you are going to go.

However, if you do gain access to a LEXIA, it can tell you the firmware revision of your gearbox ECU and that will tell you if the "new" solenoids should work or if it needs to be updated.
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Re: C8 2004 AL4 gearbox no oil pressure, tech help please!

Post by PeteC8 »

Thanks for the input, much appreciated. As the only thing I changed was the 2 solenoids and subsequently lost virtually all drive accompanied by engine management light, I can only guess that the ECU doesn't like them. My quest continues!