C5 V6 ZF 4HP20 Code P0782 2-3 Shift Malfunction

[Jan Calitz]

Hi, I have problems with this auto box. Bought car with broken gear box. Replaced with second hand unit. Will not shift from second to third. Overhauled g-box with new clutches, seals and new filter. Same fault. Replaced TCU with second hand one. Same fault. If started, it will engage all gears. If one stops, will not move from second to third. Lock-up of converter does occur. Restart car, all gears working first time and after stop, will not go into third. Cleaned and also replaced valve body. No luck. Changed and tested sol-valves. Current OK. Tested with Lexia. If driven softly on accelerator all gears will work even after a stop... Lexia also reports P1728. Checked all wiring. OK. Noticed that the torque value that TCU received is a negative value. After start, the tiptronic will operate for all gears. Stop, and tiptronic will not shift from second to third or forth. Had car at dealer but I get impression that I know more than Tech. They suggested g-box rebuild. When fault appears, one can feel if pedal is released that it stays in second binding. Could brake "F" not emptying? Reverse and first always works correct. I have re calibrated ECU and TCU with Lexia. Cant find updated software files and cant get 4 digit security code to do download.
I have repaired the box myself but could not get brake "F's" free-play. Working on all types of cars for 40 Years.

[Mandrake]

Does the car have ESP ? (Electronic Stability Program)

If so there have been reports on the forum before of C5's with ESP and an Auto box holding onto 2nd gear due to the ESP computer system thinking that you are cornering or that one of your wheels is slipping. Try searching the forum for C5 and ESP, there are at least two threads I can remember about this.

The causes can be worn out / rusted ABS toothed rings which cause a weak signal to the ABS/ESP ECU, incorrectly gapped sensor or faulty sensor, any of which can cause a problem without necessarily logging an ABS sensor fault.

Another cause believe it or not is fitting different size tyres on different wheels! This can happen even if the tyres are nominally the "same" size, but are different brands, as different brands of tyre in supposedly the same size can differ quite significantly in rolling radius. If you mix different rolling radii on the same axle the ABS/ESP ECU will think you are taking a corner when you are driving straight ahead.

The reason this can cause gear change problems is one thing that ESP will do is hold the current gear under certain driving conditions such as cornering or skidding, to prevent something like an undesired upshift if you are in the middle of cornering and possibly in a minor drift/skid. Under these conditions its safer to remain in the same gear until the situation has passed, and this is what the ESP system will do even if you are well past the speed where an upshift would normally occur.

Assuming you do have ESP, a way to test the ESP theory is to use your Lexia to reconfigure the car to temporarily disable ESP support in the Gearbox ECU - if the problem goes away you know that ESP is the cause, then you should check your tyre diameters carefully and ABS sensor rings and sensors. (And re-enable ESP once the problem is fixed!)

[Mandrake]

Found the threads for you:

http://www.frenchcarforum.co.uk/forum/v ... =3&t=43198

http://www.frenchcarforum.co.uk/forum/v ... =3&t=42277

http://www.frenchcarforum.co.uk/forum/v ... =3&t=42691

[Jan Calitz]

Hi Simon, Thanks a lot. I do have a error on wheel 3 speed sensor battery being faulty. Any suggestions on how to replace this battery? Had a look at sensor but can not see any battery? Perhaps a lost of supply? Regards, Jan. BWT tyres was replaced by same and still new.

[Mandrake]

I suspect "battery" is a poor translation from french, as ABS/ESP wheel sensors won't have batteries in them.

Can you post a screenshot of the fault code description ? Also, a good way to confirm a wheel speed sensor fault is to jack that end of the car up and spin the wheels by hand while watching the live wheel speed data from the ABS ECU on the Lexia...

If you have a faulty wheel speed sensor then there is a good chance this is your problem. Is it not causing your ABS fault light on the dashboard to come on though ?

[Jan Calitz]

Thanks Simon, Disabled the ESP. Drove slowly to filling station for some petrol. Pump attendant came to me and showed that there is a puddle of oil under engine. It is transmission oil. Drove very slowly back home. Will have to take transmission out late next week. Did not test sensors but inspected and all seems well. Will do sensor test. If transmission is out I may as well do a check on clutches.
Do you know what play on brake :f: should be? Could not find value.
Any idea why oil leak from torque converter seal? I have replaced it with new one from repair kit.Regards, Jan.

[Jan Calitz]

Hi Simon, Checked both rear wheel sensors in ABS ECU. Speed comes through fine. Will send some screen shot later. Jan

[Jan Calitz]

Hi Simon,
Screenshots. Car standing. Engine not running. I do not want to start engine due to gearbox low oil level. We unfortunately cleared all trouble code. Found ECU plug "B" for Can buss was not fully in. Corrected. But TCU shows which gear selected but ECU, ABS and BSI does not show gear selection. Only shows a few question marks. Possible comms fault?
Kind regards,
Jan Calitz




https://drive.google.com/open?id=0B6g9L ... REVk1RbFdV
https://drive.google.com/open?id=0B6g9L ... AtUVMtclhF
https://drive.google.com/open?id=0B6g9L ... RNZlVVaFVn
https://drive.google.com/open?id=0B6g9L ... xQM1E2LXJz

[Hell Razor5543]

If you decide to strip down that gearbox CitroJim has done a very good article, covering everything you will need;

http://www.eastment.net/4hp20/4hp20_introduction.htm

[Jan Calitz]

Thanks, I have seen this one. There is a very comprehensive repair manual written by Citroen on the web. It deals in every thing. Even the speed maps etc. The document has got 250 pages. Also covers the hydraulic circuits. All clutch measurements except for brake "F" free play information. I have used this one to rebuild this gearbox.
Regards,
Jan Calitz.

[Mandrake]

Thanks Simon, Disabled the ESP. Drove slowly to filling station for some petrol. Pump attendant came to me and showed that there is a puddle of oil under engine. It is transmission oil. Drove very slowly back home. Will have to take transmission out late next week. Did not test sensors but inspected and all seems well. Will do sensor test. If transmission is out I may as well do a check on clutches.
Do you know what play on brake :f: should be? Could not find value.
Any idea why oil leak from torque converter seal? I have replaced it with new one from repair kit.Regards, Jan.

Sorry Jan,

I can't help you regarding the torque converter oil leak - that's well outside my expertise. Citrojim would be your best bet (hopefully he reads this) as he has rebuilt several 4HP20's now and knows them inside out.

Hi Simon,
Screenshots. Car standing. Engine not running. I do not want to start engine due to gearbox low oil level. We unfortunately cleared all trouble code. Found ECU plug "B" for Can buss was not fully in. Corrected. But TCU shows which gear selected but ECU, ABS and BSI does not show gear selection. Only shows a few question marks. Possible comms fault?
Kind regards,
Jan Calitz
https://drive.google.com/open?id=0B6g9L ... REVk1RbFdV
https://drive.google.com/open?id=0B6g9L ... AtUVMtclhF
https://drive.google.com/open?id=0B6g9L ... RNZlVVaFVn
https://drive.google.com/open?id=0B6g9L ... xQM1E2LXJz

Some strange readings in some of those screenshots, especially the last one, but keep in mind that if the engine is not running some real time data figures may be invalid, for example "actual torque 242 Nm" is clearly bogus when the engine is stopped. However I would have expected the ESP system to be able to read the gear lever position even with the engine stopped though.

What the Lexia does confirm is that your car does have ESP, and that the ESP system has its "hooks" into the gearbox ECU and engine ECU as well, so I suspect your original problem prior to noticing the oil leak is still ESP related, as you say it could possibly be a CAN bus communication fault between the various ECU's, if you're sure all the wheel sensors are OK.

Unfortunately that gearbox oil leak is going to stop you from progressing any further on the original diagnosis for the moment as you need the engine running to get sensible readings and it might even be necessary to have a co-pilot drive the car for you while you look at the ESP live data in real time during the drive - if it was my car that's the approach I'd take to figure out what was going wrong, as looking at the live data from the gearbox and ESP ECU's whilst the car is faulting should indicate where the problem lies.

One other thing worth checking which I think you can do with the key on but engine not running - log into the gearbox ECU and make sure that it shows the current gear lever position, eg 1,2,3, D etc as you move the lever... If it doesn't give a correct reading on this there may be a problem with the multi-switch on the gear lever. That could also potentially cause a lower gear to be held, as it might think the gear lever was in 2nd when it is not.

Usually on an ECU controlled auto box only park/reverse/neutral/drive do something mechanical inside the box via the control arm - 1,2,3,D positions are all the same mechanically (the lever moves but doesn't do anything different inside the box for these 4 positions) and relies entirely on the switch to signal to the ECU which gear you want held. (if any)

Best of luck with the oil leak fix and hopefully Citrojim can offer some words of wisdom there.

[xantia_v6]

I think that ESP seem to be the most likely culprit, but have you checked that the replacement gearbox has exactly the same ratios as the original? If any of the gear ratios or final drive ratio are wrong, then the ECUs will get confused.

[Jan Calitz]

Hi, Thanks for information. OK the replacement gearbox is not the same. This one comes from Peugeot 406. Gearbox model is 1019 000020 and part number 9631953380. I can not get any gear ratios on this box on the web.
The original gearbox was a mod no. 1019 000054 and part number 9641750080. Ratios are 1: 2.72, 2: 1.48, 3: 1 and 4: 0.72 with final drive 3.35.
I do not have the insides of this gearbox as every thing was destroyed. I do still have the two aluminium casings. Where can I obtain the ratios for Peugeot? I believe that TCU can not being programmed if ratios are different?
Regards, Jan Calitz.

[xantia_v6]

The Automatic Choice parts catalogue ( https://www.automaticchoice.com/uploads ... 8505184131 ) gives different part numbers for the "spur gear" for those transmission variants, which is not a good sign, but there is not enough information there to give a definitive answer.

[xantia_v6]

Regarding the brake F clearance, I think that http://oto.to/schematy/automat/4HP20%20 ... manual.pdf gives the procedure and measurement.