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Problem with the exhaus system (flaps, valves, always-open w. special problem)


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Hi there Lambo fans,

i own a yellow Gallardo LP 500 Coupe with less than 20.000 mls on it and have a weird problem with my exhaust (flaps) system.

As i learned with some earlier posts, a lot of the Gallardo owners upgrade their exhausts from standard LP 500 to the LP520 one - and also mine was upgraded that way before i bought it.

My car came with some problems, sorted out most of them but there still remains something that bugs me ;)

The flaps are always open, as they should be as a default mode in the construction. The computer-activated solenoid valve opens up below around 3.2K RPM - normally. My valve just stays closed and it is really loud from the beginning and i want to change it to its "original state" - working as it was intended to be. I want the car to be quiet when starting up.

I already checked these things:
- Fuse No. 9 in the rear fuse box behind the seats - working fine
- Vacuum from the "vacuum hose" - works fine
- Flaps - work when i connect the hoses bypassing the valve - they close immediately
- Valve itself - applied 12V DC via power adapter - opens immediately, closes when power is disconnected

Then i noticed that the cable with the connector that should give power to the valve does not apply 12V DC when the car is running so i assume that there is the problem.

My questions are:
- Are there any fuses to be taken care of?
- Do you think the power cable may be the fault? e.g. disconnected (from where?) or damaged?
- Could there be any other issues like a faulity signal from the ECU or a bad computer part i dont know yet?
- I searched a lot but did not find a solution / the same issue. One forum member said that the valve closes after 60seconds, and i did not wait that long. Maybe I am doing it wrong? Could just not imagine that the car starts soo loud and then quiets up ;)

Would appreciate help so much. I love this forum and would be so happy to give back when i am deeper into the topic. Will also be happy to provice pics and documentation when fixed!

Best regards!

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Sounds like you've already done most of the diagnostics.  You've demonstrated that you have vacuum and the flapper valves operate when you connect the flapper valves directly to the vacuum line (bypassing the solenoid valve).  You've also proved that the solenoid valve works by connecting 12V to it directly.  So it looks like the problem is no 12V command signal from the ECU.

There's a chance the wire from the ECU is open circuit.  The most likely place is at the connector on the solenoid valve.  Pull the flexible boot back from the connector and verify that both wires are firmly connected to their pins (see first pic).  The green/black wire is the signal from the ECU, the purple wire is ground (I think).


If there's no problem with the connector, the next step would be to see if there's signal at the output of the ECU.  The Gallardo has two ECU's; you want the one behind the left seat (the driver's seat for those of us in the US).  You can remove the connector backshell and probe the cable to locate the same green and black wire you found on the connector.  You can probe this with a voltmeter by poking the probe through the wire insulation (and then start the car).  If you don't see 12V here, you've got an ECU problem.  If you see 12V here, but not at the connector, then it's a break in the wire somewhere between the two.


As a final word, I would STRONGLY recommend dumping the factory exhaust and going to an LOC (LNB?) exhaust (the version without the valves).  The even-fire V10 sounds fantastic with the LOC X-pipe design, much, much better than the LP-560's or the Huracans. It's loud all the time, but it's a very "nice" loud, much more pleasant than the muffler-bypass (flapper valves open) on the stock muffler

Good Luck,




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Hey @doltmo, thank you so much! This was really helpful and i am with you, this is what i should check next. Could you help me again with one question: Several people told me that the Gallardo starts up with open flaps, but as it is so (!) loud, i cannot imagine. Do you know if there is a delay between cold starting the engine and the 12V DC Signal to the solenoid valve?

Another guy told me that the flaps are 100% closed even at cold start.

He told me that there could be a switch i dont know yet ;) and i just want to make sure that i dont measure at the ECU when there is no fault but just a delay. Also, another guy told me to check the fuses in the front passenger side. Could that be a helpful hint, too?

I really feel great with the support i got from your side for my first post. Happy to be here and soon be able to share my expierience + helping others.

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Both answers are partially correct.  Remember that the valves are normally open (loud) and are closed (quiet) by vacuum.  The vacuum comes from the engine intake manifold when the throttle is closed or only partially open. The 12V solenoid valve is normally "closed" and opens when 12V is applied.   An energized/"open" solenoid valve allows engine vacuum to reach the exhaust valves and close them, making the car quiet.

So the car is LOUD under the following conditions:

(1) no vacuum, OR

(2) solenoid valve de-energized (no 12V)

By simple logic, the car is QUIET when

(1) there is vacuum AND

(2) the solenoid valve is energized (12V)

There is a vacuum accumulator in the system (a plastic bottle with a one-way valve) that maintains vacuum during wide-open throttle for other systems in the car.  Upon initial start-up it takes a few seconds for the engine to "pump down" the accumulator and generate enough vacuum to close the exhaust valves.  This is why the car is loud on initial start.  The other times the car is "loud" is:

(1) full, or near-full throttle (no vacuum produced by engine) - regardless of engine RPM

(2) engine RPM above about 4500/min, at which time the ECU turns off the solenoid valve - regardless of throttle position

I'm not well versed on the ECU control, it may close the solenoid valve on initial start but I always assumed the loud start was due to lack of vacuum.


Also, the 2006 and later GEN1 Gallardos bypass the muffler completely when the exhaust valves open,  The 2004 and 2005 cars only bypassed part of the muffler and were not as loud when the valves open.  The 2007's and later had tighter emissions controls and would throw a CEL if the mufflers were bypassed other then when the ECU thought they were - something to do with monitoring the back pressure, I think.

When the car is idling, there should be 12V on the solenoid valve.  There is no other "switch" in the line between the ECU and the solenoid - unless you want to add one to select between loud-all-the-time and quiet-most-of-the-time mode.  Is there is a chance a previous owner added one of these?  Some of these were wireless/Bluetooth-controlled and tapped into the ECU wiring - either at the fuse box or at the ECU itself.


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Hi @doltmo, thanks a lot! I really appreciate your detailed description, thoughts and references.

I am really sure now that there is no 12V at the plug so i have to check for the cable, will do that now. If someone hid a switch between the ecu and plug, he hid it really well ;) did not find some modifications like that yet.

Hope to find the solution; cant really imagine that the cable is broken... weird.

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Hi! I think i found something. As mentioned earlier, i think that the 12VDC Signal does not reach the valve and that there was some manipulation going on. So i had a look under the driverside rear backlight and found a "random" disconnected cable. I think this was used before to get 12VDC from the lights (was not able to remove the whole light yet because i did not want do take off the wheel etc.) and i think that there maybe was a remote controlling unit for the valve installed and then removed later on before the purchase (?). So my thesis is that the cable to the solenoid was disconnected somewhere near that point just before it enters the bigger cable hose collecting different cables on the way to the ECU (sorry for my english... understandable? ).

I isolated the cable now correctly to avoid any damage.

Will keep you updated if i find the solution by myself or have it fixed by a professional dealership.

Btw the metal and the rear bumper really do not look very great...


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