CaliTT2001

I'm experiencing an oil pressure warning on my main LED screen after finally putting my car back together after a clutch job. I've done some googling and my situation seems maybe strange compared to others that I read about, so I was wondering if anyone has any insight about what's going on before I give up and tow it to my mechanic.

Here's the relevant info:

1. Took the car apart, swapped the clutch/plate/flywheel/slave, put it back together. It was my first time doing something like this, so it took me a while and I may not have been as graceful working in there as I could have been..

2. Took it for a test drive, it felt *great*, better than it ever has.

3. No warning lights of any sort went off during the drive. But then I parked it, immediately after I turned off the ignition I got some beeping and the red oil pressure warning symbol in the center of the LED screen, as well as an oil pressure sensor warning light in the top area of the LED screen. It struck me as odd that these warnings were going off *AFTER* turning the car off. Every story I've seen involving these warning lights has had them coming on during a drive while the engine is running. They're pretty persistently going off even after I remove the key and leave the car and lock it. After some mucking around I get them to turn off. I didn't have time to deal with it then and there because I was about to leave for a week, so I left it parked in the garage.

4. A week later, I get back, and (I realize now after doing some more reading that this was foolish, no need to tell me further :/) turn the car on. No warnings, no problems. I take it for a test drive, again it drives beautifully, no warning lights. Again the second I turn the engine off, the same oil pressure and oil pressure sensor warnings come on. This time, I also notice that the engine temperature gauge is reading high (one tick from max). I pop the hood, and I notice a hissing noise coming from the general region of the many pipes and hoses coming out of the driver's side of the engine. Couldn't identify exactly where. I get under the car and take a look at the engine oil pressure sensor, seems attached and fine.

5. I get my VAGCOM out and see if I can grab some codes. I get many:

18010 - Power Supply Terminal 30
P1602 - 35-10 - Voltage too Low - Intermittent
Readiness: 0000 0000

01314 - Engine Control Module
004 - No Signal/Communication - Intermittent
00778 - Steering Angle Sensor (G85)
004 - No Signal/Communication - Intermittent
01324 - Control Module for All Wheel Drive (J492)
004 - No Signal/Communication - Intermittent

00849 - S-contact at Ignition/Starter Switch (D)
30-10 - Open or Short to Plus - Intermittent
00667 - Ambient Temperature Signal
29-10 - Short to Ground - Intermittent
00667 - Ambient Temperature Signal
30-10 - Open or Short to Plus - Intermittent
00562 - Sensor for Oil Level/Temperature (G266)
29-10 - Short to Ground - Intermittent
01314 - Engine Control Module
49-10 - No Communications - Intermittent

01560 - Passenger Door
59-10 - Can't Unlock - Intermittent
00849 - S-contact at Ignition/Starter Switch (D)
31-10 - Open or Short to Ground - Intermittent

00857 - CD Changer Unit (R41)
49-10 - No Communications - Intermittent
02218 - Satellite Radio (R146)
49-00 - No Communications


6. A little later, I notice that there's a small fluid leak under the car on the garage floor. I can't track down where it's from, but I wipe the fluid up and it has a pink/peach hue on my white paper towel, which makes me think coolant. I take a bit of coolant from the reservoir and put it on the paper towel to compare, and they're not quite the same. The fluid that leaked has a peachier hue, where as the coolant is pure pink. I'm guessing that it's probably coolant that got discolored from dirt/grease it picked up on the way to the ground, but I don't know.


My thoughts: I realize that there are about 1001 things I could have manhandled while I was in there doing the clutch job, and this could be a combination of many disjoint problems that I caused. I was prepared for this possibility when I decided to do the clutch job myself (more for learning purposes than saving money). The fact that there are tons of codes relating to no signals and sensor problem with ECU/AWD/Oil pressure/Etc makes me afraid that I did something very bad to the electronics/wiring, and that's what's causing my oil pressure warning, and that the high engine temp and hissing comes from an unrelated coolant leak from me manhandling hoses/lines? There was a point at which some brake/clutch fluid leaked into the engine bay, and I did my best to clean it up, but I'm sure I didn't get it all... is it possible that this fluid could have eaten away at some wiring or something? Or maybe there's just one thing I forgot to plug back in as I was putting everything back together?

If there are any suggestions on things I can investigate on my own, I'm game to try. But I realize that it's likely that the car should go straight to a mechanic on this one. Given that the oil pressure warning only ever goes off AFTER turning the engine off, and never while driving, do you think that the car might be safe to drive to my mechanic? I ask because I live on a very narrow and windy mountain street and it would be annoying to get a flatbed up here. Any idea why the warning lights are only coming on after shutting the engine off?

Anyway, although it's probably headed to the mechanic, any thoughts or comments on what's going on, or anything I might want to try would be appreciated!! The clutch job itself was a great learning experience for me, and hopefully this aftermath can be too!

CaliTT2001

Additional piece of info that I forgot: The car wouldn't start before I tried to take it on its second test drive (a week after the first), but it was because the battery needed a recharge (it's an old battery). Recharged the battery and it started up fine then went on the test drive. Is there a chance that all of these intermittent sensor fault codes came from having low battery voltage while trying to start the car and they got stored?

Walpole5

Have you tried printing out the codes, then clearing them?

CaliTT2001

Yes I've cleared the codes, but I'm afraid of test driving again because of the low oil pressure warning, which seems independent of any battery failure (it went off after both times I test drove the car, independent of the time inbetween that the battery failed).

I suspect that most of those codes I pulled are indeed from the low batt start. But I can't tell until I test drive again, which I'm not sure if I should. The truly strange thing here seems to be that the oil pressure warning and oil pressure sensor warnings (on the LCD screen) are only coming on *after* shutting the engine off. So there's definitely something going on, but hopefully it's not actually low oil pressure because the warning's not coming on while driving. I'm considering cleaning all of the contacts for the sensors that I disconnected and reconnected during the job and then test driving... would this be inadvisable?

CaliTT2001

Alright, so today I tried a few things with the following results:

-Unhooked battery, unplugged all of the sensors that were touched during the clutch job (including the oil pressure sensor), sprayed with contact cleaner and waited for them to dry, hooked them back up, as well as the battery.

-Cleared codes

-Turned on the ignition and let it idle until it reached full operating temp. Turned it off, no engine oil pressure warning light. Scanned, no codes.

-Took it for a two minute light test drive around the block. Turned the engine off, no engine oil pressure warning light. Scanned, no codes!!

-Took it on a longer 5ish min test drive to the store, turned the engine off... engine oil pressure light goes off, as well as oil pressure sensor warning Scan, aaaand codes are back. I just realized that when I posted the codes earlier, I didn't say what modules each group of codes were from. I'll correct that here:

Module 01: Engine

18010 - Power Supply Terminal 30
P1602 - 35-10 - Voltage too Low - Intermittent
Readiness: 0000 0000

Module 03: ABS Brakes

01314 - Engine Control Module
004 - No Signal/Communication - Intermittent
00778 - Steering Angle Sensor (G85)
004 - No Signal/Communication - Intermittent
01324 - Control Module for All Wheel Drive (J492)
004 - No Signal/Communication - Intermittent

Module 17: Instruments

00849 - S-contact at Ignition/Starter Switch (D)
30-10 - Open or Short to Plus - Intermittent
00667 - Ambient Temperature Signal
29-10 - Short to Ground - Intermittent
00667 - Ambient Temperature Signal
30-10 - Open or Short to Plus - Intermittent
00562 - Sensor for Oil Level/Temperature (G266)
29-10 - Short to Ground - Intermittent
01314 - Engine Control Module
49-10 - No Communications - Intermittent

Module 35: Centr. Locks

01560 - Passenger Door
59-10 - Can't Unlock - Intermittent
00849 - S-contact at Ignition/Starter Switch (D)
31-10 - Open or Short to Ground - Intermittent

Module 56: Radio

00857 - CD Changer Unit (R41)
49-10 - No Communications - Intermittent
02218 - Satellite Radio (R146)
49-00 - No Communications

-Waited a bit, cleared codes checked and didn't find any coolant leak, and engine temp was fine. Drove the car home around the corner, as I was getting back into my driveway, engine temp started going up. Shut it down, oil pressure warning, and oil pressure sensor warning come on, codes come back. I investigate for a coolant leak, and I'm pretty sure the leak is coming from the flange on the driver's side which is apparently common, and seems like it's probably its own issue.

So, I'm going to replace the coolant flange. As for the oil pressure warning and the codes, it seems like something electrically weird is going, and hopefully not actually an oil pressure issue.

Some questions:

1. The battery is in the last quarter of its life, and in my VAGCOM scans the battery voltage appears to have been in the mid-high 12s when running and high 11s when not. The battery obviously needs replacing and I'm going to do that. Is there still a chance that all of these codes and possibly also the engine oil pressure warning might have to do with the bad battery (even though the car never failed or hesitated to start in any of today's events)?

2. If no, what kind of other electrical issue, if any, might cause this kind of strange behaviour? (esp. the engine oil warning light coming on *after* shutting the engine off, and persisting after I've left the car with the keys)

3. A lot of the codes have to do with open/shorts to plus or ground... is there a chance they're being cause by incorrect reattachment of the ground/plus hard lines when putting everything back together? They look like they're in the right place, and reattachment seems pretty straightforward, not sure how I could have messed that up...

4. Any other troubleshooting ideas I should try before throwing in the towel? The mechanics I've spoken to have indicated that their diagnosis will likely be expensive given the situation, which is totally understandable, so I'd like to try anything else that I can.

Thanks for any thoughts on this!!

Walpole5

I have seen some very odd behavior from VAG cars with batteries that were dying. Our previous 2007 VW Eos with a dying battery would start fine, but the windows wouldn't go up, warning lights on the dash, climate control acting weird, etc. You are suspecting the battery, so I would go ahead and install a new one. I just did in our TT, expect to pay $200.

J. Patterson

Agreed. I have seen weird stuff too with a failing battery. NAPA is a good source for an exact fit battery if you don't go OEM.

CaliTT2001

Thanks for the feedback, everyone.

Yesterday I installed a new battery and also replaced the coolant flange to fix the coolant leak (did the coolant temp sensor and gasket while I was it), and did a full coolant flush because the old stuff was G12 and the only new stuff I could get was G13.

During the times I was turning the car on and off to idle and run water through during the flush, everything was well behaved and I thought that maybe the new battery did the trick. After the coolant flush was done, I started backing out of the driveway to go for a test drive, and, just in case, decided to turn the car off one more before leaving the drive way to make sure the warnings weren't coming back.... they came right back The oil pressure warning on the LCD, the oil pressure sensor malfunction warning on the upper part of the LCD, and all the codes that I mentioned earlier, all back. Vacgcom scan clocked 12.6V on the battery while scanning when the car wasn't running, so it seems like battery's not the issue.

Two new observations:

1. The oil pressure and oil pressure sensor warnings don't seem to come on until after removing the key from the ignition entirely... removing the key seems to somehow be triggering them.

2. It seems like the cause of the failure of the coolant flange was a small oil leak coming from somewhere on that side of the engine, causing the O-ring to swell and fail. The oil leak seems very small indeed, since my oil level is right at the full line on the dipstick (goes up past the textured part of the dipstick to where the top part bends). Does the leak being small make it unlikely to be causing oil pressure issues (I'm still hoping the problem is electrical in nature)? Also, if the oil reading on the dipstick is up at the bend, does that indicate overfilling? It seems right on the line to being overfilled... looks like my mechanic did a pretty sloppy job on my last oil change (there was spilled oil all around the cap).

Any more thoughts? Thanks for your ideas!

J. Patterson

Whoa! I remember some posts from way back about this. Read up on the temperature sensor causing oil pressure warnings. Here is one example.
https://www.audiworld.com/forums/tt-...ensor-1809081/

CaliTT2001

Interesting! I did just put a new temp sensor in though.

But this makes me want to guess (hope) that there's just some shared common plus or ground somewhere that's gotten messed up, which is causing all of the sensors that share it to experience problems...

I wouldn't be surprised if there were a how-to/guide out there for diagnosing these kinds of electrical problems, and should be searchable, but I haven't been able to find anything by googling... does anyone know of something out there that I could read to help me do this? I have a Bentley manual with all the wiring diagrams, I'm just not sure exactly what to test and how. But I'm wanting to learn. If anyone could point me in the right direction on that I would be grateful