PRNDS on solid - cranks over but won't start

[bbogert]

Hi all,
I hopped in my rs6 a couple weeks back and it cranks no problem, but won't start. I noticed that PRNDS were all lit up solid, no blinking. After some time and fiddling, PRNDS went away and she fired right up. On the way home about 15 minutes later under light acceleration it felt like the trans popped in to neutral and again PRNDS. More fiddling/time and again it went away and I drove uneventfully for about 2 weeks.

Then 2 days ago while driving at a steady 30 MPH again it feels like it pops in to neutral and PRNDS. Managed to get PRNDS to go away and made it home, grabbed vagcom and it just shut off on its own and hasn't started since - PRNDS and radiator fans running full speed. Have not noticed any slippage at any point in the tranny, always pulled strong to date. Clicking over 106,000 miles, had it since 60k and maintained well.

I have reseated the ECM/relays under the hood, checked all the fuses and am going to reseat the TCM today and check for moisture. This time, no luck getting PRNDS to go way. Oddly the radiator fans turn on after maybe 15-20 seconds once the key is turned and run continuously. I have read about the sensor under the shifter and will be looking at that as well, but the fans running makes me think its not as simple as that. Loose wire somewhere??

The missing ECU errors are concerning, but not totally sure if that could mean the one under the hood on drivers side, or the transmission one under the passenger seat.

Would be grateful for some guidance where I should focus my attention first.

Vagcom showing:
-------------------------------------------------------------------------------
Address 02: Auto Trans Labels: 01L-927-156.lbl
Part No: 4B0 927 156 FL
Component: AG5 01L 4.2l5VT USA 0305
Coding: 0000002
Shop #: WSC 00000 785 00200
VCID: 76E99E52022A2D91457-513C

1 Fault Found:
18258 - Powertrain Data Bus
P1850 - 003 - Missing Message from ECU

-------------------------------------------------------------------------------
Address 03: ABS Brakes Labels: 4B0-614-517.lbl
Part No: 4B0 614 517 AD
Component: ESP 5.7 RS 6 2310
Coding: 06697
Shop #: WSC 00000
VCID: 63CFD706F1B8A839129-513C

2 Faults Found:
18258 - Powertrain Data Bus
P1850 - 35-00 - Missing Message from ECU
18258 - Powertrain Data Bus
P1850 - 35-00 - Missing Message from ECU

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

Address 08: Auto HVAC Labels: None
Part No: 4B0 820 043 AM
Component: 4B0820043AM A6-Klimavoll
VCID: 74EDA45A44563F817B3-2580

3 Faults Found:
01274 - Air Flow Flap Positioning Motor (V71)
41-10 - Blocked or No Voltage - Intermittent
01314 - Engine Control Module
49-00 - No Communications
01206 - Signal for Duration of Ignition Off Time
27-00 - Implausible Signal

-------------------------------------------------------------------------------
Address 56: Radio Labels: 8E0-035-192-RNSE.lbl
Part No SW: 4B0 035 192 P HW: 4B0 035 192 P
Component: RNS-E US3 H49 X---
Revision: 05S Serial number: AUZBZ7E1116664
Coding: 0509613
Shop #: WSC 32093 133 55480
VCID: 2A517A228612397111F-5178

4 Faults Found:
00858 - Connection; Radio Intermediate Frequency (IF) Output to Antenna Amplifier
011 - Open Circuit
Freeze Frame:
Fault Status: 01101011
Fault Priority: 5
Fault Frequency: 3
Reset counter: 103
Time Indication: 0
Date: 2015.01.08
Time: 09:18:41

Freeze Frame:
Mileage: 655350 km
Count: 801
Clock: 09:23

00852 - Loudspeaker(s); Front
011 - Open Circuit
Freeze Frame:
Fault Status: 01101011
Fault Priority: 5
Fault Frequency: 1
Reset counter: 63
Time Indication: 0
Date: 2015.01.08
Time: 09:18:17

00857 - CD Changer Unit (R41)
004 - No Signal/Communication
Freeze Frame:
Fault Status: 01100100
Fault Priority: 5
Fault Frequency: 1
Reset counter: 63
Time Indication: 0
Date: 2015.01.08
Time: 09:19:07

02005 - Coding Pin
004 - No Signal/Communication
Freeze Frame:
Fault Status: 01100100
Fault Priority: 5
Fault Frequency: 1
Reset counter: 63
Time Indication: 0
Date: 2015.01.08
Time: 09:18:27


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

I appreciate any and all help!

Bren

[DHall1]

Trans wiring harness

Bulk connector at trans and tcu

[lswing]

Didn't this just happen to kraut(?), similar circumstances. Water logged TCU? It's easy to get to, just pull up passenger carpet railing lift carpet. You could also lift the cowl just below the windshield and check the big drain plug and main fuse area on passenger side.

As mentioned, that bulk connector can loosen and get water/junk and corrode.

Best of luck!

[kruat]

Yup just happened to me...nearly same codes. Check for a water logged TCU under the passenger carpet.

[ben916]

This happened to John (Audi5000csqt):
the connection under the center console where the shifter connects to wiring harness was either frayed (sic) or partially connected.
I remember that Fidelity covered it but it was not cheap.

[Bigglezworth]

This happened to John (Audi5000csqt):
the connection under the center console where the shifter connects to wiring harness was either frayed (sic) or partially connected.
I remember that Fidelity covered it but it was not cheap.Probably required the entire engine and tranny to be removed..... :lovl:

[bbogert]

Much appreciated, will pull the carpet, check it out and update when I've checked it out. Thx!

[kruat]

In my case, I had at least 3-4 inches of water under the carpet. PRNDS was lit, car would drive in safe mode, which I think is third gear. Had to get another TCU, found a MTM chipped one for 300.

[ben916]

Probably required the entire engine and tranny to be removed..... :lovl:

Winner Winner Gluten Free Chicken Dinner!

[mik15]

did you check the ECU fuse as well? i had that once and it was the ECU fuse which had blown due to a short on the engine wiring, one of the spark plug connectors had shattered and pins inside were no longer isolated....same error message "Missing Message from ECU", so it makes me think there is something wrong with your ECU and not TCU, as both your ABS and TCU have the same error message....

either way let us know what you discover under the carpet regarding the TCU.

[bbogert]

So no moisture at all at or around the TCU, pulled the connector and it looks brand new- TCU board looks fine as well visibly. Checked ECU fuses at driver door and the 40 amp one thats right next to the ecu under the hood - all good.

Next steps are pulling the center console and checking the wiring there, and the sensor which detects which gear the shifter is in. And checking the trans wiring hardness at the trans per DHall. Short of that, anything else I might check before I tow to the shop?

I've been gathering all the parts for the the 01e conversion over the last year and a half waiting for that fateful day the trans goes. Been fortunate thus for to have no mechanical issues aside from just regular maintenance in 4.5 years or so. Pretty sure I have everything but the shifter trim/knob, clutch, and the transmission brackets/mounting right. If she's going to the shop, then its time to get the conversion done, I've been waiting for an excuse! I'm just across the Golden Gate bridge from SFO, any suggestions on a local guy/shop that can do that job would be very much appreciated. I understand Avant Werks in Truckee, CA is capable, I'm going to call them on Monday but its a bit on the far side @ 3.5 hours away.

Thx again for all the input!

[MaxRS6]

Are you chipped? My APR chip came loose and the car would crank but not start. Chip soldered back in and all good.

[kruat]

Might wanna check your connections at the main ecu as well, make sure there's no viable damage. Cooling fans coming on could mean theres a cooling system fault as well. But I didn't see it listed the list you posted.

[bbogert]

Are you chipped? My APR chip came loose and the car would crank but not start. Chip soldered back in and all good.


I had the APR chip for about 25 days. During that time for the first time since I'd owned it I started having strange trans things - mis shifts, trans error on dash which I would clear only to have them come back in a few days. That's when I began gathering parts for the 01e conversion. In the end I sent back the APR chip for a refund (it was a pricey chip anyway, and I came to the realization that I wanted to go manual when trans goes anyway which means I'd have to get flashed from someone else cuz apr doesn't do manual with their flash). Since the APR was removed, I haven't had a trans issue since in about 1.5 years.

Is the bulk connector for the trans visible from underneath the car (without dropping everything :-))? I checked everything that is visible from below and all connectors look good/clean.

I did pull the shifter to check the magnetic sensor in there for cracks and it looks fine as far as I can tell. The gear indicators all work as I move the shifter through the gears.

MAIN SYMPTOMS:
1. After key is turned on, the "step on brake" light next to P on the shifter turns on, the immediately turns off (with a click at both on and off). On for like a 1/2 second
2. PRDNS lights up after "step on brake" goes off
3. Radiator fans go on full after about 10 seconds
4. Turns over but doesn't start

Codes were mentioned above. My feeling is the ECU is gonzo. When I vagcom > Select Control Module > Option 01-Engine under Common, I get a "No response from Controller" error. Everything else I have checked in there, granted not everything, I get at least a response. I did pull the ECU and all solder points look ok.

I'm stumped! Should I check any relays under the steering wheel that may be related to the ECU? I did open up the 219 relay next to the ECU it is working.

[kruat]

So your VAGCOM won't even communicate with the main ecu?

[lswing]

Drop another ECU in and see I guess. Sounds like your trans is weak/toast though, can't handle the greatly increased torque. Both of my trans fails had similar symptoms.

[bbogert]

lswing, i only had the trans issues while the apr chip was in, and haven't had any issues in a year and a half tranny wise--- been fine.

Correct, no response from ECU when I vagcom > Select Control Module > Option 01-Engine under Common. Are there any relays I could check that might make the ecu unresponsive?

Anyone have a spare ECU I can try that lives near San Francisco?? :) I have an '01 S4 but its a 6 speed manual, kinda thinking it wouldn't be a good idea to put that in...

[lswing]

150 extra torque does strange things...hope you can get an extra ecu in there, maybe someone will chime in!

[Bigglezworth]

Remember ECU's don't just Plug N Play. They need to be configured/coded to match the immobilizer requirements of the car they are going in to which would then mean they would need the same going back to who you borrow from...

[kruat]

Ya I'd have to look at the wiring diagram once I get back to work, but there is a main relay located near the ecu. If it is bad then power won't get to the ecu. I just don't remember at this time which one it is.

[mik15]

Remember ECU's don't just Plug N Play. They need to be configured/coded to match the immobilizer requirements of the car they are going in to which would then mean they would need the same going back to who you borrow from...

or if you have good soldering skills, open up both ECU's and switch the eprom's boards

[bbogert]

My soldering skills are 'ok', I wouldn't trust myself soldering on such a critical component w/such a small working area... I'm guessing the ECU relay is the black 219 just next to the ECU, but that is a total stab in the dark -- the 219 does appear to be working, relay engages when key is turned. If there is one under the steering wheel that any one knows of I'd like to check that one. Is there a wiring diagram posted any where for the ECU? Also need to check to see if the ECU is getting power, but not sure which pin(s) are + and -.

According to RossTech:

Possible Causes Blown fuse for control module - all checked

Wiring Harness issue - need to check power to ECU. Other than that I'm at a loss-

Failed control module - not sure how to test this other than just swap with a known good one. If I understand correctly, the car should start if using an ECU that's not coded for my VIN, but would immediately shut down. That would be proof enough I think to show it is a failed ECU if it starts up even momentarily. Or if PRNDS were not all illuminated.

Possible Solutions Inspect wiring and terminals for CAN BUS between control modules.
Special Notes As per TSB 01-07-54, do not replace the ECM for this DTC. Please see TSB for complete details.


Given that this started out as a somewhat intermittent issue, I'm inclined to think either relay somewhere or loose wire.


Thanks again for the replies, I appreciate it.

[ben916]

Didn't Nene have some strange issue were it was something simple like the speed sensor?

Also, someone stated that they have seen some green corrosion on ECU pins, might be something else to look at...

[bbogert]

Update: I hauled the beast to my mechanic who has determined the ECU is gonezo. He bypassed the relays and confirmed power is getting to the ECU, but none of the other systems can talk with the ECU so apparently its dead. He says there's nothing more he can do, it has to get fixed by Audi because Audi is the only one that can program the ECU for my car. Is that true??

I'm looking for an ECU, if anyone has one I'm interested. I have an appointment with Audi next Thursday (soonest they could do!). New ECU is $1300.00 according to my mechanic. Should be back up and running soon.

Thx again for the advice, very much appreciated.

[lswing]

How much do you trust this mechanic?

There are a few threads on here about coding another ecu to your car (so your guy was close), maybe $150 at the dealer to have that done? Used ECU for ~$300?

Use the site:rs6.com to search using Google, or maybe others will chime in with the exact info.

[bbogert]

Hi all,
My RS6 is back online -- turned out to be a failed ECU. Started out intermittent as noted in original post, then just stopped working at all. PRNDS lit when key turned, and radiator fan kicked on full speed after about 10 seconds. Vagcom showed no communication with ECU. Hopefully this info helps someone with similar issue.

So, $1300 for a new ECU from Audi + 1 hour labor -- could have been worse I suppose.

I had sent the original ECU to a company called AES Modules in Florida to repair it, but they said they couldn't remove the chip for some reason and offered to sell me a new ECU from Audi for $1300, so I used that quote at the dealership to get it for that price and saved a couple hundred bucks. I got the car back and its running great, but I noticed the cruise control isn't working. Could that be a coding issue on the replacement ECU? They were unable to pull any info off the old unit.


Thanks again for the input through my 'crisis'!! :-) Bottom line, I'm back on the road

[dab]

I just had the same thing happen with mine, ecu came loose overnighted to apr they fixed for free and sent back.

[RS Sick]

I've got the dreaded APR loose chip symptoms. Had the weird crank no start issues after alternator install, all fuses including 200a/150a mains were good. Wasn't communicating with vagcom but somehow randomly fired up last night. Took the beast out for a ride and it just died while slowly accelerating, PRNDS and MIL lit up amongst others. Crank but no start again so pushed it off the road and did vagcom again, same issue as OP, fans come on ~10 seconds while running scan. P1850

BTW, the car died on me exactly once (when parked) right before alt replacement and I was noticing low voltage so rebuilt anyway. Any thing else I should check or just send ecu off to APR for fix?

17592
17593

[RS Sick]

17594
Here's another picture, don't have laptop to paste full scan.

[bbogert]

I've got the dreaded APR loose chip symptoms. Had the weird crank no start issues after alternator install, all fuses including 200a/150a mains were good. Wasn't communicating with vagcom but somehow randomly fired up last night. Took the beast out for a ride and it just died while slowly accelerating, PRNDS and MIL lit up amongst others. Crank but no start again so pushed it off the road and did vagcom again, same issue as OP, fans come on ~10 seconds while running scan. P1850

BTW, the car died on me exactly once (when parked) right before alt replacement and I was noticing low voltage so rebuilt anyway. Any thing else I should check or just send ecu off to APR for fix?

17592
17593

Hey, I'm no expert thats for sure. But this does sound exactly like the issue I had > PRNDS flashing followed by the fan running full bore. Its worth noting in my case, the issue happened once then self corrected for a week or something. Then got bad quick over a few days. I was able to restart the first few times i got the PRNDS flashing by fiddling w/the key, checking fuses etc, but I really think it was dumb luck that the car did fire. I didn't have APR programming in the car when the issue occurred, but I did do an APR trial (for a month) like a year prior to the issue. If I recall the 3rd party I tried to get to fix the ECU (some company out in Florida) but told me they couldn't repair it because of how a chip had been replaced/soldered on the board > I'm not sure if that was an APR thing or not. I couldn't send it to APR because I had returned the product.

Sounds like in your case the new alternator may have fried a chip on the ECU? Or it could just be a strange coincidence. In my case, no changes were made directly prior to the issue.


Good luck!

[nubcake]

<...>new alternator may have fried a chip on the ECU?<...>

Highly unlikely.
No communication with VAG-COM and fans full-on are usually a good indication of something bad happening inside the ECU.

[RS Sick]

I had the alternator rebuilt because I noticed ~12 voltage while driving over a week or two. It died on me and did PRNDS (while parked) exactly once before I messed with alternator.

APR chip was indeed the culprit. They re-soldered and were able to reuse the ecu. Their chip technology really is inconvenient. Reinstalled and all has been well over the last week.

The positive outcome is downtime allowed for sportec vent mod, order of aces IV and quantum blue oil. Pulls like a freight train.