AudHaus

My 98 A8 entered limp-home mode once before, but without a code when I later checked it. It did it again recently, and I checked the codes prior to shutting off the car. It threw the following tranny code:
18242 - Pressure Control Valve 5 (N233): Open or short to ground P1834 - 35 - 00 - -

In both cases it happened while stuck in traffic for a while, and finally starting to go again. Engine revved strangely high (like no clutch engagement) and then some rock-hard, abrupt shifts, one of which eventually throws it into limp mode.

Fluid completely changed 14K miles ago. Fluid still full and clean.

Anyone have experience with this, or know what the pressure control valve is?

Karpedmman

Aud- Trannys are complex items. To increase your knowledge base I'm giving you a copy of the ZF manual for our trans. P. 34 shows an exploded view of the "Valve Body". This is where your error is occurring. These valves open and close and cause the vehicle to shift. (Basic) What is the car doing now? How did you get it corrected the previous time? Did you clear the code this time and does the code return?

I lost my transmission about 9 months ago so I became educated real fast on these beasts. I know the abrupt shift and teeth rattling clunk you describe. It is definitely NOT a good feeling.<ul><li><a href="http://www.zf-group.com/pdf/5HP24A.pdf">http://www.zf-group.com/pdf/5HP24A.pdf</a</li></ul>

PaulW

Will have to look it up when I have the Bently...but it sounds like you have a problem with the valve itself. If it's one of the three proportional valves....it's just not working correctly, if it's one of the 5 two position valves that control the hydraulic control circuit for shifting gears....then it won't set up the proper hydraulic circuit.

I'll have my PC back tonight with the Bently...can give you an idea then. But if it does need to be replaced....will be easy to do.

You can also hook up vag-com....do an output test on the tranny....then check fault codes. Look at the table and see how much current it should draw or if it should be on/off (depending if it is proportional or two position valve) and monitoring it while driving.....easy to do.

Replacing it is the same as a fluid filter change plus dropping the valve body and changing it. Shouldn't be that hard.

pw

Terrybill

Thanks for a fabulous link!!!

AudHaus

Normally, once you shut off the ignition, and turn it back on, it is no longer in limp mode and appears to drive fine -- until the next time. Right now, I'm hyper-sensitive to its shifting, and it doesn't seem quite right, including entering limp mode again as I entered my driveway, from what appeared to be only very slightly abnormal downshifts.

I did not clear the codes, as I wanted a record of it, since the first time it happened, there were no codes later. I'm happy to finally have a clue.

I did not see any mention in the PDF file of pressure control valves. Does it cover them?

AudHaus

The Bentley! Duh! I'd forgotten I have it, since I've frequently found it nearly useless and haven't needed it in so long. It does say that the pressure regulating valve 5 either has a short to ground or open in the wiring, or is malfunctioning. The 16-pin connector to check is inside and involves removing the ATF sump and having access to the valve body, which has the various solenoids and control valves. I can't tell if it is necessary to remove the valve body to change the pressure regulating valve.

Regarding the output test using VAG-COM, how do you do this? The Bentley describes it in terms of their tool. I've really only used VAG-COM to read and clear codes.

By the way, the tranny's shift mode is set to the more agressive European setting, (whatever that is - I can't recall), though I seriously doubt that is relevant to the problem at hand.

PaulW

If you go to the Bently....automatic transmission, OBD, perform output tests....it states:

Output Diagnostic Test Mode (DTM) (function 03)

Notes:

The output DTM can only be carried out when the selector lever is in "P" position, the engine is running <b>***I don't think this is correct*** it should be off</b>, and the vehicle is standing still.

The output DTM is discontinued when the engine is started.

The function of the solenoid valves 1 -N88-, 2 -N89- and 3 -N90- and the shift lock solenoid -N110- are checked audibly during the output DTM. During the audible check the surrounding noises should be limited, since the clicking noises are very quiet.

Pressure control valves 1 -N215-, 2 -N216-, 3 -N217-, 4 -N218- and pressure regulating valve 5 -N233- are triggered by the output DTM. A direct functional check of these components is not possible. However, electrical malfunctions, which occur during this triggering, are eventually stored in the DTC memory through the OBD program.

During the output DTM the individual controls are triggered until the button is pressed.

Only a complete final control diagnosis is possible after the ignition is switched on. To repeat, the ignition must be switched off and switched on again.

----------------

These are the prerequisites.....so the first thing you want to do, open a Word document, copy your exisiting codes using the ross-tech software....then paste it in word and save it.

Clear your codes....I would then reset your ignition.

Put the car in P and with the engine OFF (it says to have it running above, but I don't think it will do it then and you won't be able to hear anything, try it both ways), select "transmission" then 03 "output tests" then click on the "start test" button, then click it a bunch of times until it is complete, it has to do all eight valves.

Then go back and check for fault codes.

If you want to check the solenoid electrically, you could do it from the electronics box in the engine compartment, you don't need to pull the pan.

The other thing to do is to do a measuring block test (test 08) and click up to channel 06, measuring block 4 monitors the current draw of solenoid valve N233 (your problem child)....it should be 0.0 minimum to 2.0 maximum during driving mode.

If you go to page 37-43 of the bently....Automatic transmission....Automatic Transmission - Controls, Housing.....transmission shift elements.....then scroll down, you'll see when it should be energized and not....then drive around and check it out.

I just got a Tungsten T3 palm and I think I will get the software for monitoring so I can do things like this really easily.

Good luck, tell me what you find, be happy to help you out.

pw