Another thread regarding the " P026A 00 [237] - Efficiency Below Threshold" code

JETaah

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Another thread regarding the " P026A 00 [237] - Efficiency Below Threshold" code

Yup, like it says.
EDIT:
model year corrected

The car is a 2014 Passat and it is getting the below code:

12642 - Charge Air Cooler
P026A 00 [237] - Efficiency Below Threshold
MIL ON - Confirmed - Tested Since Memory Clear
Freeze Frame:
Fault Status: 00000001
Fault Priority: 2
Fault Frequency: 1
Mileage: 141822 km
Date: 2031.14.31
Time: 13:39:33

Engine speed: 1535.00 /min
Normed load value: 51.8 %
Vehicle speed: 81 km/h
Coolant temperature: 77 °C
Intake air temperature: 63 °C
Ambient air pressure: 990 mbar
Voltage terminal 30: 14.260 V
Unlearning counter according OBD: 40
Air mass at air mass meter 1: 99.0 kg/h
Temp sensor for low-pressure EGR after cooler: raw value: 67.5 °C
Outside air temperature: 1.5 °C
Intake air temperature before throttle valve: calculated: 27.2 K
Sensor for temp after charge air cooler: raw value: 63.7 °C
Coolant pump for charge-air cooling: spec. value: 95.00 %
============
From what I have read in all the threads, it seems like the cause was due to having a winter front installed and that prevented air flow from creating enough difference between the in and out of the intercooler.
There is no winter cover on this car. So what gives?

Could it be the intercooler's coolant pump? Looks like it is at 95%
Does that mean it is almost full on?

What kind of measurement is the 27.2K ?
i.e.,
Intake air temperature before throttle valve: calculated: 27.2 K
 
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Rico567

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We have used the idparts winter fronts on our '13 Passat since new and have never had a problem.
 

JETaah

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We have used the idparts winter fronts on our '13 Passat since new and have never had a problem.
But, there have been more than a few that have had problems.
That will not be the problem on this car.
 

meerschm

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does the 2015 passat have a grille shutter? if so, you should be able to operate it with VCDS.
 

JETaah

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does the 2015 passat have a grille shutter? if so, you should be able to operate it with VCDS.
I did not see anything to that effect in the output tests.
One thing I did notice today is that the aux coolant pump runs a long time after the engine is off.
And, the pump did not shut off while performing an output test on/off sequence .

I could see that if a temp sensor is reading high that it would cause the pump to run until it satisfied the programming. The only temp sensor that I see is just past the intercooler right near the intake flap.
 

VeeDubTDI

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Things to check:

1.) Air blockage/restriction through the intercooler's radiator (winter front, excessive accumulation of road debris/dirt, bad cooling fan(s), etc.)
2.) Coolant blockage in the intercooler (air lock, bad pump, etc.)
3.) Bad intake air temperature sensor

Is this 2015 still under warranty?
 

JETaah

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Not under warranty anymore. 88K miles.
Does it have it's own radiator in front of the engine rad?
 

VeeDubTDI

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Correct. Separate radiator that shares the same reservoir. The two coolant circuits operate in an isolated fashion normally - the connection is just there for filling/priming.

I'm not sure if that diagram is completely accurate for the 2015 Passat. I believe the intercooler is a different design and is mounted differently than depicted there. I could be wrong though - I haven't looked at a 2015 Passat TDI in a while.
 

JETaah

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The intercooler on the car looks pretty much dead-on like the illustration.
 

compu_85

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I'd suggest trying to get the intercooler pump to run with the engine off (perhaps there's an output test for this?) and listening for the motor / coolant flow.

How's the heat in the car? Is it as warm on the passenger side as the driver's side?

-J
 

BKmetz

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2015 Passat, titanium beige, 6MT
I believe there is some clarification needed on how the intercooler is set up.

2012 to 2014 NMS Passats have the EA189 engine family that has the CKRA engine code. The intercooler looks like the diagram in the link. The intercooler is a separate unit that bolts to the intake manifold. I believe the CKRA intake manifold is made out of plastic.

2015 Passats have the latest EA288 family of engines that has a CVCA engine code. While looking very similar to the CKRA engine it has quite a few differences including the intercooler. The intercooler is cast as part of the intake manifold and is all cast in aluminum. Here is a pic of the CVCA intercooler.



If this is indeed a 2015 with the intercooler shown in the link, it's a CKRA engine. I was under the impression that all 2015s used the newer CVCA engine. But this is VW and they could have built some early 2015s with the CKRA engine.

Unfortunately this information does not help diagnose/resolve the problem. My thinking follows that to see an intercooler code one should see a very high coolant temp first. I can only imagine what a PITA back flushing the intercooler would be.

I too also use an IDParts grill cover on my 2014. There have been ZERO issues with it on the car. I have had a few oddball warm days in late winter where the temps reached 60F and the engine ran just fine. Coolant temps were always within the normal range ~210F per Scangauge-II.

Good luck.
 

JETaah

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Well..........
My Bad!
Apparently this is a 2014 car..."E" letter code in the VIN.

I corrected this in the first post.
 
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JETaah

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I'd suggest trying to get the intercooler pump to run with the engine off (perhaps there's an output test for this?) and listening for the motor / coolant flow.

How's the heat in the car? Is it as warm on the passenger side as the driver's side?

-J
The coolant pump works audibly and I can feel it in the hoses.
As stated above, I shut the car off and did the output test for the pump.
At that time, the pump was still after-running and the test did not override the sequence to turn it off on command via the output test.

And, Yes, I first saw this car a year ago and the owner did have the complaint about the uneven cabin heat. I referred him to the VW dealer for help on that one. I don't know if he had anything done about it.
Was this known to cause trouble in more than the heater core itself?
I suppose that since it shares coolant with the engine/climate control, any crap that was produced could have migrated to the intercooler circuit. Good thought!
 
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VeeDubTDI

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So the theory a few of us have is that the contamination that fouls the heater core will also foul other coolers with small passages. This could be the oil cooler, the EGR cooler or even the charge air intercooler (even though its coolant loop is semi-separate from the main engine loop). So far nobody has verified any of this happening, but I also don't think anyone has actually checked for or encountered one of these conditions.

Regarding BK's engine coolant temperature observation, since the two loops are semi-separate, each with its own radiator and control circuit, it's entirely possible for the charge air system to overheat without the engine overheating or vice versa.
 

251

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And, Yes, I first saw this car a year ago and the owner did have the complaint about the uneven cabin heat. I referred him to the VW dealer for help on that one. I don't know if he had anything done about it.
When I got my 2014 in January 2016 the heat worked "well enough" until just prior to Thanksgiving 2016 when it quit. Only got cold air at that point, took it to dealer and heater core replaced under warranty. Wow - what a difference with new core! I now have to turn the heat down once the cabin quickly reaches a comfortable temperature which was not the case with the original core.

My point here is if the heater core has not been replaced yet on this customer's NMS it will not be blowing hot air, would be more like warm air and over time should slowly get cooler until the core fails. If the heat is indeed blowing hot then core probably got replaced. Why not ask customer if core got replaced? It may help the troubleshooting efforts here - at least you'll know if it may be a factor or not.

Since it is cold and if you still have this car on hand what does the heat feel like once the temp gets up to the normal range during a drive?
 

compu_85

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As stated above, I shut the car off and did the output test for the pump.
Oops. I should read more carefully :eek:

I should follow up to the above post: The NMS's heater can pump out some really really hot air. I should measure the vent temps on ours. It is noticeably hotter than the Mk4, or the old Benz.

-J
 

JETaah

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I had to give the car back to the owner but, I found out that the heater core was replaced by VW and most likely the coolant was as well so it would be hard to tell if there is any sediment floating around in the reservoir that would contribute to clogging the IC.
I will probably see this car at the next oil change.

Did anyone experiencing the heater core corrosion issues notice any crud in the reservoir?
 

VeeDubTDI

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I had to give the car back to the owner but, I found out that the heater core was replaced by VW and most likely the coolant was as well so it would be hard to tell if there is any sediment floating around in the reservoir that would contribute to clogging the IC.
I will probably see this car at the next oil change.

Did anyone experiencing the heater core corrosion issues notice any crud in the reservoir?
If the heater core was recently replaced, I would try to find out if the intercooler loop didn't burp all of the air out when the system was refilled. If there's an air pocket trapped in there somewhere, it could be preventing water flow through the intercooler system.
 
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