2002 Audi A6 suddenly stalled out.

5

Asked by Aug 17, 2015 at 10:21 AM

Question type: Maintenance & Repair

I need some help regarding my 2002 A6. Recently it suddenly stalled out in perfectly good weather but after we'd had a long period of almost daily heavy rains. It restarted a 4-5 times very briefly but stalled again trying to put it in gear, now permanently.

Because of the previous wet weather here are the things I've done:
Checked Roof drains - clear.
Checked Firewall plenum - clear (removed battery & its tray and manually cleaned/ checked the drain)
Checked E-Box - clear & dry.
BUT the adhesive sealing foam gasket under the E-Box is wet and perished.
Pulled all E-box relays and checked them out functionally w/ digital meter.
Cabin air intake tray (the elevated part around the opening) had water and had clearly overflowed into the opening.
Like the E-Box, the adhesive foam gasket was soaked and perished.
Passenger side carpet had some free water on the carpet, but not much and but it was largely beaded up on the surface rather than soaked in.
A ground point attachment to the left of the cabin air intake shows a lot of mineralization and start of corrosion.

Since the stalling event, after turning the ignition to ON, after about a 5 second delay, the radiator cooling fans come ON HIGH.
Over past few weeks of drying out in the summer heat and under cover, the fan running has changed to running after 5 second for about 30 seconds then shutting off, repeating this cycle.

Initially I suspectedfuel system (because it did fire-up a few times),
I checked the following:
Vacuum lines - all AOK (new silicone lines)
Fuel pump fuse - OK
Terminal 30 of FP relay socket 13V
Fuel Pump fuse socket supply side 3.6V
Jumpered the Terminal 30 of Fuel Pump relay socket to
(1) the fuel pump - Fuel Pump RUNS BUT Engine does not fire.
(2) supply side of fuel pump fuse - Fuel Pump RUNS BUT Engine does not fire.
Concluded that Fuel pump is either bad or terminals T and 86 are not energizing the relay's solenoid.
Replaced with NEW fuel pump relay - still 3.6V at supply side of fuse, no run no start.

So here are the questions:
What specific sudden event could cause the voltage drop from the fuel pump relay?
Are there other components which are switched / serviced / actuated by the fuel pump relay?
What component is failing to energize terminals T and 86, thereby not energizing terminal 30 to 87?
What other component could reasonably be affected by or fail in relation to the voltage drop?
What other sensor failure could cause such a chain of events?

It seems to me to be either something shunting current from the FP relay at T-86, or another fuel or fire component is also not actuating T-86 as a result of a voltage drop. such as cam or crank sensors, fan relay or controller, ignition lockout, security lockout.
How is the radiator cooling fan's actions related to this?
Any help would be appreciated.

44 Answers

520

You might have a Bad crank position sensor. I have few a6 that when the crank sensor goes bad it have no power to fuel fuel pump. Try read fault codes and write down the faults and erase them and try to crank enough to create new codes and ready again and replay. Good luck Ariel Krankenwagen European Car Specialist.

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Best Answer
5

First of all, thank you for replying. I suspected the CP sensor but I don't know how to test it. I'll look it up, test it and post what I find, If necessary, I'll order a sensor I'll do that and post the results.

520

Do you have a obd2 scanner that you can read the memory of the ECM ?

1 out of 1 people think this is helpful.
5

Yes I do,

5

It's new to me so I have to study OBD2 manual and the Audi manual to know what to look for with and in the scanner. Also, I can't find in the Audi manual where the CPS is located and its connector is so I can test it with a multi-meter.. Seems like there is no standard place on all the Audi engines.

520

The crank sensor is located on the transmission bell housing right above the drivers cv axle. But you can erase the fault memory of the obd2 and crank for short periods but feaw times until the ECM gets not feedback from the crank sensors and it triggers the new faults

1 out of 1 people think this is helpful.
5

Thank you once again! I'll try getting the codes with OBD2, but as I said I'm very proficient with it. Also, I don't think mine has access to a lot of Audi / VAG codes. It's an Autel MaxiScan MS509. Can you tell me where the connector from the CPS is located so I could test it with a multi-meter also. I'm guessing it has to be near the E-box. I have an idea of the of the mV (2-400) output and ohms (800 ish) resistance I should see. If access to change or test the CPS is from underneath, then I couldn't do much right now because the car is parked where I can neither lift with a jack to get under, nor move it have more room to work around it (it's blocked in for a few days at least!). I'm charging the battery right now because it's been getting run down from multiple starting attempts.

5

Correction: I'm NOT very proficient with OBD2

520

The conector is next to the coolant tank you have a light grey conector that's your guy

1 out of 1 people think this is helpful.
520

And the maxidas hand scanner you have is good to read the vag codes just take a pick with your phone and email

520

Sorry. Thank a pic of the maxidas screen with the readings and email it to me to thekrankenwagen@gmail.com

5

I've sent pics of the scanner screen.I don't even know if I'm looking in the right places. Also, I sent pics of what I understood to be the CPS connector. Could you verify? BTW, there is a very obvious ground point connector on the firewall about 6" above and to the left of the CPS connector. Is this the ground point responsible for the primary circuit of the fuel pump relay solenoid?

520

That ground it should be couple of brown wires going to a single nut make sure they are all connected and good contact otherwise car will acting up and by the way I can open the pics :-(

1 out of 1 people think this is helpful.
5

Can't open the pics, or can't open the zip files?

520

Cant open the zip files from my iPhone or iMac

1 out of 1 people think this is helpful.
5

OK glad you got them now. I got a copy of the Scanner codes list cross-referenced to Audi. It looks like I should see an error code P0600 for a problem with the CPS, but my scanner doesn't see it. I can see the pale gray connector but it's a bear to get to because it's behind several hard vacuum and coolant lines which make it difficult to pull the connector's mounting bracket forward off the firewall far enough to pull the plug. Plus, it has one of those annoying locking connectors which is facing the wrong way to get the tool onto it. But I haven't given up yet! re pic 12 Why the generic P0001 code with "Fuel volume regulator control circuit / Open"

5

Well, I finally got the connector off the firewall - A crazy place to put that connector. Anyway, I tested the CPS with a muti-meter across all three leads (i.e. all three pairs of black, pink, blue). All combinations show open circuit.(infinite ohms). Verified with two different meters. I'll order a new one tonight and should have it Friday.

520

Where did you order the sensor?

5

RockAuto

520

Awesome!!!!!

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520

I'm sure the crank sensor will do the trick :-)

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5

Thanks for all your help. An acquaintance, now retired, told me once that the Bentley was a poor manual. I've now discovered he was right. Very poor coverage of trouble shooting common issues. For example: Crankshaft Position Sensor is not in the index. Unbelievable! I'll let you know when I have the CPS installed.

520

Cool

5

Well, after wrestling with this under the car for days in 90 degree heat, stuck bolts, screws, connectors, etc etc., I finally got the CPS installed. Anyway....It has not fixed the problem. The car is still dead. Apparently Audi calls the Crankshaft position sensor the Engine Speed Sensor. There are no stored codes in the computer that my OBDII sees, so I'm at a loss what to check next.

520

Did you put the aluminum round spacer from the old sensor to the new one?

1 out of 1 people think this is helpful.
5

Yes I did, thanks I think the second culprit to try would be the Coolant Temp Sensor. It's cheap, quick and easy DIY. I should have done it first in retrospect. BTW passing the connector & cable up to the firewall was pretty easy considering how tricky it looked.

5

Oh I almost forgot. Some cases I read people reported the Coolant temp sensor threw no codes before it packed up and gave this crank-no fire-no start scenario. Thought this might be useful info.

520

I have never experienced coolant sensor doing that but just by disconnecting the sensor will eliminate your doubt

520

I'm wondering if you are off timing! Take a look at your belt just to make sure it didn't snapped or jumped

5

I think the belt is fine, about 20K on it. It's tension is fine, so no reason to jump. Also, the 3.0 L being an interference engine, it would surely crash simply on cranking with a broken belt wouldn't it? Your suggestion to try disconnecting the CTS sounds logical. I'll try disconnecting it in the morning. Something interesting did happen: Recall that the radiator cooling fan started acting up, running on high after 5secw/ key on. Now, since I installed the new CPS the instrument display at key-on now displays a giant thermometer indicating coolant overheat even with the motor stone cold. It did not do this before. It's entirely possible (possible but not common) to have two problems at the same time.This makes me think both the CPS and CTS are both involved because of the extremely heavy rains in the spring. Both could have been affected by the heavy rains near and under the plenum drain. Water is one thing that can affect a lot of systems all at once. One more weird thing, according to Audi even with a no-start situation, functional CPS, and cleared codes, cranking for at least six seconds an OBDII should show those rpms on a new read of live data. I get nothing. More info tomorrow.....

520

There is something kind of weird here!!!! Is like something is shooting down the ignition. You mention that the passenger side carpet was wet. If your car is Quattro I will suggest you to lift the carpet in the passenger side and see if the Tcm is getting moist or water I will actually do both side to also check comfort convenience. Without the proper equipment we going to keep looking until we find the root of this problem. With a vag-com we can see how is the network is communicating. If there is a bad module somewhere it will shoot down any component in the network. I have a Allroad that will start only at times and end up been the Tcm wet due to sunroof drain leaking inside vehicle.

1 out of 1 people think this is helpful.
5

The temperature sensor arrived yesterday. It rained all day so couldn't try it until today. I just pulled the connector off and pushed the new on to test it. Still the same - no start. I have no way of checking if the belt jumped, but it's intact, not loose, and the car is not doing that futile coughing noise trying to start when it has fuel and fire when out of time. I had an older 90 one time do that so I know the sound. Funny you mention the computer under the passenger side carpet, because it occurred to me too. I'll check that tomorrow. BTW, with new crank & temp sensors do I need to reset the computer to clear anything? Also you mentioned a module causing a network shutdown. Does the OBDII error message (600) I mentioned a while back have anything to do with that? I've been thinking I should just buy a Ross Tech VCDS because I'd at least know what's wrong. Around here you can't get out of an Audi repair shop for under $1k just for a "Hi, How are ya?" and It's funny they can find all the expensive "You need this as well" items but only do the minimum on what you really need. I'm fortunate my old 90 still runs well, so I'm not stuck without transport.

5

I agree with you. It does appear, and has from the beginning, that something is shutting down both fuel delivery AND ignition.

520

On more thing, get the multimeter and measure the voltage at the fuel Pump fuse and write down how much voltage you have and after that remove the fuse and measure the side both side of the connectors and if you have more voltage after you remove the fuse them there is chances something is shorting out the line.

5

I have measured voltage before and after the fuse already - it is 3.6 volts. Terminal 30 to the FP relay is 12.8V. I get the same voltages with a new relay What I've been doing is trying to determine where the voltage drop is happening. As I said previously I want to get access to the back of the relay panel to check the voltages at different point between its out put terminal (87 I think) and wher it finally reaches FP fuse #20 (I think). The relay actuates correctly in the car and when tested out of the car it does not have a voltage drop. Unfortunately, I haven't checked the climate(?) computer under the passenger's carpet yet. I'll try to get to that tomorrow. There is something else I just noticed. When I put the key in in the ON position (not cranked), a relay or actuator of some at the air intake at the back of the motor, just in front of the coolant temp sensor, starts clicking and clacking randomly. I don't understand how the strange electrical activity of the cooling fan (high and low) and that clacking actuator could be caused by a skipped belt. I'd like to find trouble shooting guide schematic which shows in detail the individual events that have to take place in sequence for this engine to start and run, including protective event s in sequences which lead to shut down and lock-out.

520

The clicking and clanking noise is the throttle body initiation that happens everything you cycle the ignition key. What is happening with the fan? Don't understand!!! Is the cooling fan running when you cycle the key on?

5

Both the fan and throttle body come on with the key ON, but they run in different patterns, both random. Like you said earlier, I should check under the carpet for the CCM. I did remove floor mats and the carpets were still damp after about 6 weeks in summer heat, under shelter with windows open for ventilation. So I must now assume the insulation under the carpet was completely soaked. I've now found about a dozen posts with people having similar problems, all water on the CCM. I'll make time to do pull the carpet up tomorrow. Is it drivers or passenger's side?

520

Dude I will definitely check the ECM for water migration because people always damage that cover and water short out the relays and the power supply relay and fuse are in there and when they get wet the fans go crazy I think your real problem is there and is messing up and flooding your car

520

http://www.awe- tuning.com/media/pdf/02_A4_A6_al lroad_removal_AWETUNING.pdf

5

Ok, Ariel, I'll bring you up to date with what I've done. Thank for the link. I did all that about two months ago. I checked the E-box and the ECU very early on. Both were dry and still dry today. I've protected the car from rain since it's been down. Inside the E-box nothing was not wet nor looked like it ever had been wet, BUT I found crazy stuff inside it. There were acorn shells, popcorn, a little white fluffy fuzzy ball like the ones people tie fuzzy dice to their RV mirror with, and the craziest stuff in the corners was some white foamy mineral material like foamy plaster - quite a bit of it. So obviously the E-box had been visited by mice. I don't know what the white stuff is or how it got there. I pulled all the relays and checked their function with 12V supply and a multi meter, and everything checked out OK. I thought the white mineral stuff might have been water residue, so I Removed the ECU box, opened it (I slotted the screws) and found it perfectly dry with no sign of ever being wet. However, I found the E-box seal to the plenum surface was shot due to water and the foam rubber portion has perished, so I'll be replacing the seal with either neoprene or PPT. and cement. I'll have to do the same to the cabin air intake seal to the plenum. Today I lifted the carpets in both foot wells. The drivers side is dry, and it appears to have never been wet. The passenger's side has water!!!! There is a large block of foam rubber surrounding the wires going to the CCM, and it is soaked. I can wring the water out. But it's tough to get the carpet lifted enough to get good access to remove the box, so I'll remove the seat tomorrow. One bit of good news is that the water did not smell all stinky and dirty. That means it has not been there a very long time, and the chances of saving the unit are good, Electronic circuitry can be washed cleaned and dried safely, and if there is no corrosion it should be OK. If you have any suggestions on how to lift the carpet without busting up the closed cell insulation on the bottom I'd appreciate it. Nothing in the Bentley about carpet removal in the Trim section. That closed cell stuff is to prevent surface water from getting down through the carpet, so I'd rather not damage it. I think the water got down there down the firewall.

5

Correction: nothing was wet in the Ebox

Was there ever a resolution to the above problem?

I would also like to find out what happened

5

Finally gave in and towed it to local shop a friend recommended. The answer I got was the ECU damaged by a bad ground point connection on or near the drivers side fire wall. I wasn't shown which or where exactly. ECU was replaced (recycled unit) and everything is OK. It also fixed an intermittent issue with the brakes/traction control which would randomly lock up momentarily and pull hard to the left. I don't understand how a loose or poor ground connection would cause the ECU to "burn out." Anyway, that was the resolution. My thanks to Krankenwagen for his input and time, muchas gracias!

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