Don't pull that fuse!
Discussion
Here we go again. Having pulled fuse 22 out I have now been told that its removal can cause the computer to throw up an electrical fault. This information was given to me by the service department at Broughtons. They offered instead to disconnect the two vacuum pipes which operate the valves which leaves them fully open all the time. We have had this done today at no cost. I would say that it is the way to go!! That V8 burble is now there at all revs, coupled with an assortment of grumbles on the over run. Excellent!
Removal of Fuse 22 will not, of itself, cause a Check Engine Light. There will be an error recorded in the systems which an OBDII reader can see, but that error is not one which is linked to a CEL. Error code P1488 will be stored in the PCM. There is lots of anecdotal scaremongering on this board about "as soon as I pull 22, CEL comes on" but fuse 22 removal of itself is not the cause. P1488 Will not (according to the OBD II manual) light the CEL/MIL.
robgt said:
Here we go again. Having pulled fuse 22 out I have now been told that its removal can cause the computer to throw up an electrical fault. This information was given to me by the service department at Broughtons. They offered instead to disconnect the two vacuum pipes which operate the valves which leaves them fully open all the time. We have had this done today at no cost. I would say that it is the way to go!! That V8 burble is now there at all revs, coupled with an assortment of grumbles on the over run. Excellent!
Interestingly Broughtons did that on mine too, permanently open as opposed to just popping the fuse; works for me as I have no interest in it going back in.robgt said:
Here we go again. Having pulled fuse 22 out I have now been told that its removal can cause the computer to throw up an electrical fault. This information was given to me by the service department at Broughtons. They offered instead to disconnect the two vacuum pipes which operate the valves which leaves them fully open all the time. We have had this done today at no cost. I would say that it is the way to go!! That V8 burble is now there at all revs, coupled with an assortment of grumbles on the over run. Excellent!
please no....This is nonsense. There is no problem with removal of fuse 22 from a 4.3 V8 (or equivalent fuse in other models).
It was designed to be removed - so AML could pass noise tests.
Think it through as an engineering puzzle - by default the car is noisy, but powering the circuit for fuse 22 means it's quiet. If fuse 22 fails then the car is loud. So by design the circuit fails to loud. You don't fail to a dangerous state - that's engineering 101.
It's perfectly safe to remove fuse 22.
Edited by JohnG1 on Tuesday 17th January 09:46
Slarti said:
Stratstone pulled my fuse and showed me how to put it back if needed. Other than the warning that the valve may seize if I don't occasionally replace the fuse (and risk mot failure) they were really quite blasé about it all.
I took mine in for an MOT a few weeks ago without fuse 22 ........ it passed. SL500UK said:
I took mine in for an MOT a few weeks ago without fuse 22 ........ it passed.
Perhaps Slarti was alluding to the seized valves rather than the missing fuse per se.I shall quote Mighty Mike B once again....
"...The bypass valves are present for one reason, and one reason ONLY - so the vehicle can pass noise drive-by test. The car is tested on a controlled surface which is in controlled surroundings making noise recording very accurate. The total noise the car produces is measured at a start gate, around 30MPH in third gear, the car then accelerates at full throttle to around 55MPH where the test terminates at the end gate. The engine speed and load (volumetric efficiency) conditions the car is operated under during this test defines how the exhaust bypass valves are controlled by the EMS. The exhaust bypass valves only purpose is to effectively cheat the test and gain a noise drive-by test pass for an exhaust system that would otherwise fail, being too loud....
...Removing fuse 22 electronically inhibits operation of the vacuum pump which controls the valves. The default position of the valves is 'open', so by disabling the system the valves simply sit in their default position. Prolonged usage with the valves at default open position is highly unlikely to seize or stick the valves should they be operated at some point in the future. I have also read elsewhere owners have been advised not to remove fuse 22 as they have been told it creates fault codes which disrupt the diagnostic system, or somehow creates other (electronic / mechanical) faults - Rubbish... All that happens is a PCode is simply registered within the modules history to state electronic control of the valves was not possible, this code does not illuminate the yellow 'check engine' light on the dash.
In summary - remove the fuse and enjoy the soundtrack.....!!!"
fluffer said:
I agree with the rest of you in saying F22 isnt an issue.
Just this:
"You don't fail to a dangerous state"
hmmm. So you fail to a safe state in all cases?
I wrote that. No of course you don't fail to a safe state in ALL cases. But when failure of a component would damage the system then you get a warning. For example - if your ABS fails on your car you see a warning light. If your headlight fails you see a warning light.Just this:
"You don't fail to a dangerous state"
hmmm. So you fail to a safe state in all cases?
When designing the bypass valve system the engineers had two choice - it's by default set to noisy or by default set to quiet. So by design they said - the default it noisy. You need f22 powered up to make it quiet.
If fuse 22 fails or is removed we see default behaviour - noisy. No engineer worth his or her salt would design the exhaust bypass valve subsystem to fail to a damaging state.
Take a further example - railway signals. They fail to a red light - why? So if the signal fails the train stops. Why? Impact is that the train is late and there is no train ahead. Better than failing to a green light and hitting the back of another train. Hence the expression "fail-safe".
I could go on. And on. But I'll spare everyone an engineering design lecture...
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