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Discussion Starter · #1 ·
Hello Fellow EOS Owners. I purchased a 2012 EOS Lux about 18 months ago. It had 74,000 Miles at the time. Its had a few issues that needed taken care of, but a very frustrating issue occurs every time the outdoor temps go below 20 degrees. So mainly the past 2 winters here in Colorado. The check engine light will come on. It doesn't effect the drivability or anything on the car. The light remains on until it warms back up and it will clear the fault on its own.
I have had it to the VW shop several times, first replaced a Intake manifold hose that had a leak, next was the throttle body, and after that didn't fix the problem the High techs from VW were called in to try to diagnose this issue,. The next suggestion from them was to replace the ECM. $1800 later, the problem reared its ugly head back when we got a cold snap a few days ago. The car is currently in the shop waiting for advice from VW on to what they are suggesting.
Has anyone else had this issue? I would gladly take any suggestions at this point. Now the shop I have the car into has a couple of mechanics that went to classes especially for EOS, since back when there were a lot of roof issues they got more training on that particular model. But they are scratching their heads at this point as well. I am thinking maybe a different set of eyes may be my next step. as much as I respect them, I need to get this resolved.
The car has never been in any type of accident and the prior owner took meticulous care of the car so Ive ruled those 2 things out. HELP
 

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That type of temperature related fault is really hard for them to find. I have something similar with the immo. on another vag which I think is the engine or dash ECU. Great you have some EOS roof trained techs in your local! Tell members here where they are.

The only logical way is to use diagnostics when the fault is likely to occur. Everytime the MIL light comes on, fault codes will have been stored - what where they and do they change now things have been done or are they the same fault codes?

Diagnostics can monitor real time engine values when it's running. There are things you can do with a CO2 fire extinguisher or refrigerant gas to try and provoke a low temperature related faults in electronic modules, wiring and connectors. The fault codes now stored are key to understanding what might be wrong? Even though you are in the hands of techs for this intermittent problem, you could consider buying your own V.W compatible diagnostics. Even if you don't do any repairs, it helps to build up a picture of what could be wrong at the time the fault occurs.

Is your car garaged overnight or left outside? Condensation and freezing can interfere with some of the electromechanical parts. I would rule this out if the car was kept dry in a garage overnight and the MIL light came on after driving in low temperatures. I won't throw in too many ideas, but the most sensitive fragile sensor in the engine management system is the mass air flow sensor, responsible for giving the equivalent of 'choke' in cold weather. If there were problems there, I think you would notice poor engine performance or lumpy idle on a cold start.

Electronic and mechanical parts in a modern efi engines all work together in harmony and sofware sets limits defined by V.W for 'normal' behaviour. Abnormal behaviour when something measured is out of range, or doesn't correlate with another sensor measurement is often the trigger for MIL. It can be something serious or a monitored measurement just out of range and an early warning sometimes resetting itself or cancelling the MIL light. If you haven't done mileage and got 'limp mode' it's probably in the warning category of faults?
 

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Discussion Starter · #3 ·
That type of temperature related fault is really hard for them to find. I have something similar with the immo. on another vag which I think is the engine or dash ECU. Great you have some EOS roof trained techs in your local! Tell members here where they are.

The only logical way is to use diagnostics when the fault is likely to occur. Everytime the MIL light comes on, fault codes will have been stored - what where they and do they change now things have been done or are they the same fault codes?

Diagnostics can monitor real time engine values when it's running. There are things you can do with a CO2 fire extinguisher or refrigerant gas to try and provoke a low temperature related faults in electronic modules, wiring and connectors. The fault codes now stored are key to understanding what might be wrong? Even though you are in the hands of techs for this intermittent problem, you could consider buying your own V.W compatible diagnostics. Even if you don't do any repairs, it helps to build up a picture of what could be wrong at the time the fault occurs.

Is your car garaged overnight or left outside? Condensation and freezing can interfere with some of the electromechanical parts. I would rule this out if the car was kept dry in a garage overnight and the MIL light came on after driving in low temperatures. I won't throw in too many ideas, but the most sensitive fragile sensor in the engine management system is the mass air flow sensor, responsible for giving the equivalent of 'choke' in cold weather. If there were problems there, I think you would notice poor engine performance or lumpy idle on a cold start.

Electronic and mechanical parts in a modern efi engines all work together in harmony and sofware sets limits defined by V.W for 'normal' behaviour. Abnormal behaviour when something measured is out of range, or doesn't correlate with another sensor measurement is often the trigger for MIL. It can be something serious or a monitored measurement just out of range and an early warning sometimes resetting itself or cancelling the MIL light. If you haven't done mileage and got 'limp mode' it's probably in the warning category of faults?
They are getting the same fault they were hunting down with the old ECM. Very frustrating. The car sits outside unfortunately due to limited garage space and my 2019 VW Conv Beetle SEL gets the privilege of staying in it. I do put a a half cover over the top of the EOS to help keep the seals in decent shape. I'm second owner of the EOS. Never been wrecked. Never had a car in have a check engine light come before.
So currently back in shop and VW Tech line is working on what their next attempt will be. You would think it would be an easy fix with all the computerized components these days. Get this fault, check abc. Not the case.
If I didn't like the car so much I would of gotten rid of it the first time the fault popped up. Spring and summer coming soon. Time for the top down!
 

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Don't give up. They have a hard job to trace the fault unless it's cold but they are best placed with eyes on and they know what work they have already done. Until then, they can just guess which can get expensiv for you. The computer and diagnostics may be reliable, but the parts it controls are still electromechanical. If you post back you need to give more info as to what fault codes they are seeing, which is why having your own diagnostics scanner is a good idea. As you said the car is parked outside in low temperatures and I assume the MIL light comes on soon after starting it, If all the obvious like hoses have been checked for leaks, I might suspect it's a motorised flap valve problem sticking when cold or iced up, or one of a couple of temperature sensors (including the muffler sensors) that are not giving the same temperature at the low ends as others. As well as sensing temperature, there are also sensors that measure pressures referenced to atmospheric. There are 2 of these in different places which are expected to track close together, otherwise the system sets a fault.

You haven't said how the MIL light fault first comes on. Assuming the MIL light was off when you parked the car and left it overnight, does it come on within a few seconds of turning on the ignition but not cranking? Does it come on whilst cranking? Is it off when idling, but comes on as soon as you start driving or how many minutes after driving and where is the temperature gauge when it comes on? If it doesn't come on during idle or immediately you start driving, does it come on when engine rpm is high? Is the battery good and fully charged and cranks easily when cold? These are all important bits of behaviour that help with diagnosis.
 

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I have had it to the VW shop several times,

$1800 later,
But they are scratching their heads at this point as well.
The problem with this type of post is they've had hands on the car, they have $0000s of diagnostics equipment, manufacturer info, etc. I am 6000 miles away and a couple of paragraphs to go on. I can't help with the technical aspect of the car. All I can say is, looking at it with a fresh pair of eyes, it looks like they are learning on the job but you're paying for it. I'd ask for the $1800 (plus any other labour etc) back, and pay say 1 hour's diagnostic time whatever that is.

.....And then find another garage.

It does seem USA VW dealers have a special way of not knowing if they're having a shit or a haircut when they sit down.
 

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Discussion Starter · #7 ·
Don't give up. They have a hard job to trace the fault unless it's cold but they are best placed with eyes on and they know what work they have already done. Until then, they can just guess which can get expensiv for you. The computer and diagnostics may be reliable, but the parts it controls are still electromechanical. If you post back you need to give more info as to what fault codes they are seeing, which is why having your own diagnostics scanner is a good idea. As you said the car is parked outside in low temperatures and I assume the MIL light comes on soon after starting it, If all the obvious like hoses have been checked for leaks, I might suspect it's a motorised flap valve problem sticking when cold or iced up, or one of a couple of temperature sensors (including the muffler sensors) that are not giving the same temperature at the low ends as others. As well as sensing temperature, there are also sensors that measure pressures referenced to atmospheric. There are 2 of these in different places which are expected to track close together, otherwise the system sets a fault.

You haven't said how the MIL light fault first comes on. Assuming the MIL light was off when you parked the car and left it overnight, does it come on within a few seconds of turning on the ignition but not cranking? Does it come on whilst cranking? Is it off when idling, but comes on as soon as you start driving or how many minutes after driving and where is the temperature gauge when it comes on? If it doesn't come on during idle or immediately you start driving, does it come on when engine rpm is high? Is the battery good and fully charged and cranks easily when cold? These are all important bits of behaviour that help with diagnosis.
Sorry for the delay. I took a break from the internet this weekend. The fault occurs about a minute or so once the car is started. Not while driving, before putt in gear. As for the battery it was replaced about a year ago. It cranks right up. Trust me I have thought of anything that could cause it to trigger the fault.
Currently its still in the shop. The local rep that works on these cases with the techs don't work on weekends. SO I am patiently, did I say patiently? waiting to hear from the service manager on what they are going to do next, if anything. Theres a local mom and pop shop down the street from my residence that has a big sign out in the front saying "CHECK ENGINE LIGHT ON? Bring it in.........I am tempted. My extended warranty has helped out a bit so far. I
Its warm now here so they are not going to get anymore faults which I believe hampers the search.
Will post when I hear anything......
 

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If V.W can't fix it with all their access to resources and historic fault infornmation on other cars, then I doubt anybody else can? Your engine is used in many VAG group models and there should be nothing unusual about it. But as I said earlier, they have to see the fault when it happens to start further investigation or experiment with 'enironmental conditions' to try and provoke the fault. There must some fault codes stored in the ECU log since it was last cleared.
 

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Discussion Starter · #9 ·
If V.W can't fix it with all their access to resources and historic fault infornmation on other cars, then I doubt anybody else can? Your engine is used in many VAG group models and there should be nothing unusual about it. But as I said earlier, they have to see the fault when it happens to start further investigation or experiment with 'enironmental conditions' to try and provoke the fault. There must some fault codes stored in the ECU log since it was last cleared.
Yeah there are new faults stored since the new ECM. I had taken the car over during the last cold snap so they could see it. AS you say, this shouldn't be something they never seen before with that engine in a lot of their models.
 

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V.W seem to be reducing their stock holding by stocking 'universal' parts claimed to be backwards compatible over several earlier years. That's not a bad thing. You could ask what the ECM firmware version was for what they took out and what it is now for the replacement? I'm sure V.W will have tested later versions, but their behavior in an older engine with some wear could be different? At every iteration of engine software year on year they are meeting more stringent emissions rules which change the engine fuelling. Rough running I might expect, but temperature related warnings are very strange unless old sensors have more error than an updated ECU can handle?

There are only three (?) critical temperature sensors AFIK and since they are far cheaper than an ECU, changing them is worth a punt. But the ECU should have stored more information about a temperature fault and where it's coming from. At low temperatures if the sensors are telling the truth, the engine will use a different richer fuelling map. aka 'choke' and there will be parts that have to respond within a preset range to change the fuelling. If they can't or are out of range, a fault will be triggered. What you think starts as intermittent low temperature behaviour could be sensors at the low temperature not having the correct curve or they give correct information but the control element is out of range to follow the richer fuelling map?

V.W techs will be out of there depth, but I know how I would measure a temperature sensor. Plot its curve to find its operating point at <20 degrees then replace it with a variable resistor for a short engine test. The car will think it's starting at < 20 degrees. If the MIL light comes on you know it's not a sensor fault but a part controlling fuelling. The ECU will expect the temperature value to increase as the engine warms up so the sensor value would have to be faked (changed slowly) to simulate warming up. V.W use 2 temperature technologies. MY07 Tdi has more expensive and reliable linear platinum resistance sensors for high temperature exhaust. On newer vehicles they changed over to thermistors which age and are notorious for curve tracking errors at their extreme ranges. The sensor most critical to ECU fuelling is the cylinder head sensor which is the first one I would change. This is usually a more precise sensor than the coolant sensor. Yes, the gauge can be off another sensor!
 

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Discussion Starter · #11 ·
V.W seem to be reducing their stock holding by stocking 'universal' parts claimed to be backwards compatible over several earlier years. That's not a bad thing. You could ask what the ECM firmware version was for what they took out and what it is now for the replacement? I'm sure V.W will have tested later versions, but their behavior in an older engine with some wear could be different? At every iteration of engine software year on year they are meeting more stringent emissions rules which change the engine fuelling. Rough running I might expect, but temperature related warnings are very strange unless old sensors have more error than an updated ECU can handle?

There are only three (?) critical temperature sensors AFIK and since they are far cheaper than an ECU, changing them is worth a punt. But the ECU should have stored more information about a temperature fault and where it's coming from. At low temperatures if the sensors are telling the truth, the engine will use a different richer fuelling map. aka 'choke' and there will be parts that have to respond within a preset range to change the fuelling. If they can't or are out of range, a fault will be triggered. What you think starts as intermittent low temperature behaviour could be sensors at the low temperature not having the correct curve or they give correct information but the control element is out of range to follow the richer fuelling map?

V.W techs will be out of there depth, but I know how I would measure a temperature sensor. Plot its curve to find its operating point at <20 degrees then replace it with a variable resistor for a short engine test. The car will think it's starting at < 20 degrees. If the MIL light comes on you know it's not a sensor fault but a part controlling fuelling. The ECU will expect the temperature value to increase as the engine warms up so the sensor value would have to be faked (changed slowly) to simulate warming up. V.W use 2 temperature technologies. MY07 Tdi has more expensive and reliable linear platinum resistance sensors for high temperature exhaust. On newer vehicles they changed over to thermistors which age and are notorious for curve tracking errors at their extreme ranges. The sensor most critical to ECU fuelling is the cylinder head sensor which is the first one I would change. This is usually a more precise sensor than the coolant sensor. Yes, the gauge can be off another sensor!
I went and picked up the car Monday since the service tech seemed to not have any info when they were going to hear from the VW techline. It gets frustrating when they insisted I bring it in since we had a dip in outside temp but yet the car doesn't seem to be a priority or make it a priority on their end. I needed the car and gave them 4 days but yet no info for me. I told them maybe we will try this again next winter. Of course on their diagnostic report I wasn't cooperating, by leaving the car with them for an indefinite time. The frustrating thing is they had replaced 3 components to the engine, all of which they said was the cause to the fault, and none were.
 

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I'm afraid that tends to be the way with workshops now. An intermittent fault like yours can mean a lot of hours time when they might spend the time more profitably doing easier jobs. I drove a company car once which on decel. approaching a junction and unpredictably, it would just die and stall. A real safety hazard which the garage never sorted. You probably need to think about buying your own diagnostics? Even if you have to use others for servicing and repairs, I always think if you scan first and log errors with dates, they do work and the same diagnostics errors come back, you have a bit of evidence they didn't fix the problem.

When you get these type of problems on complex electronic systems you can usually access 'working spare parts' which you can use to help track down a problem. Unfortunately, all V.W electronic parts come in sealed bags and once opened, the customer has to pay since they can't be returned. I suspect the 'non-co-operation' is on the paperwork because they have to meet targets and not finding a problem after having the car 4 days when they gave you a date would look bad for them? Being the arguing sort, I would go higher to V.W customer care and get that statement struck off and replaced by a more truthful statement? As I said before, an intermittent fault is the worst kind but they could at least have acknowledged that and stated they hadn't yet found a conclusive solution to the problem. But you would rightly argue about their bill and parts fitted without solving the problem.
 

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P0507 is usually a vacuum leak. I'd check the PCV valve, Brake Booster line, and rear main seal for oil leak.
 

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Discussion Starter · #14 ·
P0507 is usually a vacuum leak. I'd check the PCV valve, Brake Booster line, and rear main seal for oil leak.
That was the first repair they did. Next cold spell the fault came up again.
I'm afraid that tends to be the way with workshops now. An intermittent fault like yours can mean a lot of hours time when they might spend the time more profitably doing easier jobs. I drove a company car once which on decel. approaching a junction and unpredictably, it would just die and stall. A real safety hazard which the garage never sorted. You probably need to think about buying your own diagnostics? Even if you have to use others for servicing and repairs, I always think if you scan first and log errors with dates, they do work and the same diagnostics errors come back, you have a bit of evidence they didn't fix the problem.

When you get these type of problems on complex electronic systems you can usually access 'working spare parts' which you can use to help track down a problem. Unfortunately, all V.W electronic parts come in sealed bags and once opened, the customer has to pay since they can't be returned. I suspect the 'non-co-operation' is on the paperwork because they have to meet targets and not finding a problem after having the car 4 days when they gave you a date would look bad for them? Being the arguing sort, I would go higher to V.W customer care and get that statement struck off and replaced by a more truthful statement? As I said before, an intermittent fault is the worst kind but they could at least have acknowledged that and stated they hadn't yet found a conclusive solution to the problem. But you would rightly argue about their bill and parts fitted without solving the problem.
I find this funny. I told the service manager that I converse in this group about the car. He asked me to get the
I'm afraid that tends to be the way with workshops now. An intermittent fault like yours can mean a lot of hours time when they might spend the time more profitably doing easier jobs. I drove a company car once which on decel. approaching a junction and unpredictably, it would just die and stall. A real safety hazard which the garage never sorted. You probably need to think about buying your own diagnostics? Even if you have to use others for servicing and repairs, I always think if you scan first and log errors with dates, they do work and the same diagnostics errors come back, you have a bit of evidence they didn't fix the problem.

When you get these type of problems on complex electronic systems you can usually access 'working spare parts' which you can use to help track down a problem. Unfortunately, all V.W electronic parts come in sealed bags and once opened, the customer has to pay since they can't be returned. I suspect the 'non-co-operation' is on the paperwork because they have to meet targets and not finding a problem after having the car 4 days when they gave you a date would look bad for them? Being the arguing sort, I would go higher to V.W customer care and get that statement struck off and replaced by a more truthful statement? As I said before, an intermittent fault is the worst kind but they could at least have acknowledged that and stated they hadn't yet found a conclusive solution to the problem. But you would rightly argue about their bill and parts fitted without solving the problem.
I find this funny. I had told the service manager that I converse in the forum about the issue with the car. He asked me to ask you for those temperature relays you said would be a cheaper way to go so he could look up the prices for me. I find that odd when they had the techline support that I would of thought they would had suggested that at some point? I'm going to do a little investigation with customer relations and see what they think about this. I'm a little concerned about having the yearly emissions test done if a check engine light is on and would they pass the car? Normally the car would need to be repaired and brought back for the test to be done again.
Also since this fault only comes up when its 20 degrees or below I suggested taking the car into a refrigerated shop, in which we have one in Denver. His response was the last time they used it it ran them $100,000 for rental for the month.
 

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Discussion Starter · #15 ·
P0507 is usually a vacuum leak. I'd check the PCV valve, Brake Booster line, and rear main seal for oil leak.
They have replaced a leak in the breather element/intake hose? They checked everything, twice. Replaced the throttle body, ECM, per VW techs, thinking this was the cause. I still got the fault when the temp outside went below 20 degrees.
 

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Try disconnecting the brake booster line and plugging it at the pump, I had a small hole in my brake booster diaphragm that caused this once. Also you can try disconnecting and plugging the fuel tank evap line at the intake, sticky evap solenoid could also cause it.
If you can't find the problem, I'd suggest taking it to a VW Performance shop such as New German Performance, or RAI Motorsports, those places are usually better than dealership and cheaper.
 

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those temperature relays
If those are trhe EXACT words they used, then they haven't a clue about EFi engine management or how to find faults in them because there are no RELAYS. It would be like talking about valves when modern devices are full of microchips and software.

I agree on advice to try a performance shop particularly those that do ECU remapping and have dyno testing. They should be more knowledgeable on Efi engine systems than old hand wrenchers. However, the problem of stimulating the low temperature fault still has to be addressed to make the fault easier to locate.
 

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Discussion Starter · #18 ·
Try disconnecting the brake booster line and plugging it at the pump, I had a small hole in my brake booster diaphragm that caused this once. Also you can try disconnecting and plugging the fuel tank evap line at the intake, sticky evap solenoid could also cause it.
If you can't find the problem, I'd suggest taking it to a VW Performance shop such as New German Performance, or RAI Motorsports, those places are usually better than dealership and cheaper.
Thanks for the info. Altho this fault only comes on when our outside temp drops below 20 degrees. So they wouldn't be able to tell if we found the problem or not at the moment.
I was thinking I needed to get a different set of eyes on the car since for almost 2 years now nobody at the VW shop has been able to fix the issue. BTW, this check engine light will clear itself once the temp warms up.
 

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Discussion Starter · #19 ·
If those are trhe EXACT words they used, then they haven't a clue about EFi engine management or how to find faults in them because there are no RELAYS. It would be like talking about valves when modern devices are full of microchips and software.

I agree on advice to try a performance shop particularly those that do ECU remapping and have dyno testing. They should be more knowledgeable on Efi engine systems than old hand wrenchers. However, the problem of stimulating the low temperature fault still has to be addressed to make the fault easier to locate.
No, those were my translation since I'm no mechanic. I didn't appreciate his sense of humor with the refrigeration bill. If you people are in business to find the problem, why didn't you use this refrigeration building to get to the issue.
"
Please get the data on what temp sensors and I will quote replacements for you. We do have a refrigeration shop here to use it you need to rent the complex as a unit, as it is owned by General Motors. Last time VW used it was $100,000 a month."
This is what he actually said.
 

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Putting a car in a space or room and refrigerating it down to 20 costs a lot in energy. They wouldn't like getting themselves cold working in there either!
Please get the data on what temp sensors and I will quote replacements for you.
That's when they really mean they have given up or if they actually said that, they haven't a clue how to diagnose a V.W engine or have access to parts lists, wiring diagrams, understand V.W technical information and look up parts just like members here might do? They've given up on your car!

Gearslam said:
I'd suggest taking it to a VW Performance shop such as New German Performance, or RAI Motorsports, those places are usually better than dealership and cheaper.
Get the right tuning shop who work with V.Ws and Audis (even Porsche and Mercs) and they should at least understand the complex workings of Efi engines. They won't have the freezer shop, but I'm sure they can find or buy a cylinder of refrigerant gas for $75 to blast around suspect modules and much cheaper than putting the car in a cold room. I can buy a small can of aircon top up gas on Fleabay for less than that! I'm surprised they didn't suggest loaning you diagnostics with remote wireless telemetry back to base and get you driving to the North Pole. You would take Husky dogs and a sled in the back, in case the car wouldn't start to get you back to town. :)
 
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