B8 S4 intake flaps stuck closed

[Difaz]

Hi all
I’m hoping someone could shed some light on this topic. I have the following code.
P2006 and P2007 - Intake Manifold Flap Stuck Closed

I have read through as many threads as I can find on this but none seem to hit on my particular issue.

First of all the problem is intermittent and I can feel when it is happening due to the drop in power.

I have checked the vacuum system with vacuum tester and all is good. Flaps move and no vacuum drop.

I have tested the solenoid valve and it opens when power is applied.

So I did the following.
A) connected a vacuum gauge on the flap side of the solenoid to monitor the vacuum going to the flaps.
B) connected a voltmeter in to the power side of the solenoid to see if 12 bolts was getting to the solenoid to actually open the valve.

I then drove the car and observed the readings. What I found was that when everything is working and the flaps are opening, I see power to the solenoid and vacuuming to the flaps. When the flaps are not working I see no power to the solenoid and of course no vacuum.

Therefore I conclude that the problem is an intermittent power supply ( lack of) to the solenoid.
My question is what is causing this power to drop out intermittently. I’ve checked and cleaned all electrical connectors, check wires for breakage etc but visually it all looks good. I’ve also checked voltage drop across electrical connectors.

My next step I believe would be to check the circuit back to the ECU? Does anyone know the ecu pins for the solenoid valve and / or any other circuit related to the intake flaps. Also any other suggestions would be greatly appreciated as I’ve hit a bit of a dead end at present.

Thank you for taking the time to read this post.

[Allowencer]

You've done some great troubleshooting so far.

What year car? And this is an S4, not an A4?

Have you pulled on the wires at the pins to ensure it isn't a brittle connection?

You're on the right track as to the next thing. Check the circuit all the way back to the ECU. Something isn't right somewhere.

With more info, someone here could advise on each junction.

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[Difaz]

Hi Allowencer, thanks for your reply. it’s a 2010 S4.
Yes I’ve pulled on the wires and checked pins etc, it all looks ok. I don’t have a wiring diagram so a bit stuck from this point. I did pull the ECU plugs and clean all the terminals and plugs with an appropriate electrical cleaner / spray but it didn’t help. I Didn’t test for continuity due to lacking a wiring diagram.

[Smac770]

So, specifically, it's the CAKA engine?
3.0T issues are going to be more found in the S4 forum than the A4 forum: https://www.audizine.com/forum/forum....php/163-B8-S4
The 3.0T load flaps are discussed on pages 32-33 of the SSP 437.

The G336 bank1 sensor and G512 bank2 sensor have 3-pin plugs:
1 - 5V
2 - voltage signal
3 - ground

The 5V and ground are provided by the ECM, and both sensors' 5V and gnd are connected together. But only after passing through some 14-pin wiring connector.

G336/1 - T14g/7 - T94/35 (5V)
G336/2 - T14g/8 - T94/13 (signal)
G336/3 - T14g/9 - T94/39 (gnd)

G512/1 - T14g/10 - T94/35 (5V)
G512/2 - T14g/11 - T94/35 (sigal)
G512/3 - T14g/12 - T94/39 (gnd

So start by checking for 5V from pin 1 to pin 3 on the harness plug to the sensor (ignition at least probably has to be on, not sure if the engine has to be running for the ECM to turn on that 5V supply). Then I'd check the voltage between 1 and 2 and between 2 and 3. It should come up as "0" or "no reading" in both cases, because the wire shouldn't be connected to the other two wires along the run back.

If you have problems at the harness plug for the sensor, you might back up to that T14g connector wherever it is and check there. See if the issue is on the ECM side or the sensor side of the T14g connector.

If the voltage supply to the sensor is good and the signal line doesn't seem shorted to anything, then check the voltage on the signal line (relative to the sensor ground line, not vehicle ground) as the load flaps are actuated. You might be able to invoke them manual actuation, or with an output test, or using a vacuum pump on the actuator, etc.

Part of the question is "are the moveable", or has carbon buildup stuck them in place, etc. Or is there a failure of the vacuum line feeding the actuator, etc, etc, etc

[Difaz]

Hi Smac770 and Thanks for your input.
I have checked the function of the G336 and G512 sensors with VCDS and they are both working. The problem I seem to have is that power is intermittent to the Intake manifold flap valve N316. The ECU should activate this valve to open it as described in the SSP however this is not always happening. When power reaches the N316 the flaps open, when it doesn’t the flaps stay closed.
I will post in the S4 thread as you suggested also.

[Smac770]

That's a similar construct as the 2.0T. The vacuum pump is connected to the N316 input, the flap actuator is connected to the N316 output, the ECM energizes the N316 when it wants to pass vacuum and actuate the flaps.

The original N316 would develop corrosion, which is why they eventually replaced it with a 3-port variant and the vent tube that runs up on top of the engine. The N316 is powered on pin 2 by the same 12v source as many other engine devices. The pin 1 is the ground line applied by the ECM to energize the N316 when intended. So could be a wiring concern, maybe a failing terminal crimp in the harness plug, or a bad N316. The N316 is the same generic vacuum solenoid used across much of the engines.

[RPMtech147]

Was there recently work done that required pulling the super charger? I've seen MANY instances when folks not familiar with the 3.0T do the PCV valve and when they install the intake runner(s) and the blower, they pinch the runner flaps under the blower. You actually have to hold them slightly open when installing or they get stuck.

NM, you say the problem is intermittent.

The vacuum solenoids get hot and crap out. I see it a lot on the 4.2 FSI engines all the time as the vac solenoid sits right in the valley and soaks up a ton of heat. The tell is it'll be fine (you can monitor flap position) then they stick closed after a few miles and the ECU faults. At least the solenoids are easy enough to change on the 3.0T.

[Difaz]

Was there recently work done that required pulling the super charger? I've seen MANY instances when folks not familiar with the 3.0T do the PCV valve and when they install the intake runner(s) and the blower, they pinch the runner flaps under the blower. You actually have to hold them slightly open when installing or they get stuck.

NM, you say the problem is intermittent.

The vacuum solenoids get hot and crap out. I see it a lot on the 4.2 FSI engines all the time as the vac solenoid sits right in the valley and soaks up a ton of heat. The tell is it'll be fine (you can monitor flap position) then they stick closed after a few miles and the ECU faults. At least the solenoids are easy enough to change on the 3.0T.

Hi thanks for the input.

No work done that coincides with this problem starting shortly after etc.

The problem is definitely intermittent as at times the light will stay off for a few drives after clearing codes and then other times come on not long into the first drive after clearing codes. Also the loss power of power and response is very noticeable when the flaps don’t open so it’s obvious, and very frustrating when it’s happening .

I did test the solenoid by supplying 12 V directly to it. When I did this it clicked and allowed air to pass so it seemed to be working. It could still be faulty since the problem is intermittent? Would be nice to find the problem rather than to start replacing parts and hope it works. Perhaps I can wait for flaps to stop working and then test the solenoid by the side of the road, since you mentioned it could be heat related this is definitely worth investigating. Other option is just change the valve which is what I’m tending towards at this point.

[Allowencer]

Was there recently work done that required pulling the super charger? I've seen MANY instances when folks not familiar with the 3.0T do the PCV valve and when they install the intake runner(s) and the blower, they pinch the runner flaps under the blower. You actually have to hold them slightly open when installing or they get stuck.

NM, you say the problem is intermittent.

The vacuum solenoids get hot and crap out. I see it a lot on the 4.2 FSI engines all the time as the vac solenoid sits right in the valley and soaks up a ton of heat. The tell is it'll be fine (you can monitor flap position) then they stick closed after a few miles and the ECU faults. At least the solenoids are easy enough to change on the 3.0T.

Ya know, this guy does call out a hell of a good point. Heat can cause issues. You could test with a heat gun and warm up the solenoid and check voltages. Or just replace it and see if the issue returns at that point.

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