Got a fault code on my 2007 FH, its
MID 128 PSID 98 FMI 1 Boost Air System, Value to low.
Found out a bit about fault codes on interweb, seems to be Turbo or EGR related. Although mines a Euro 5 with adblue and I thought that was SCR not EGR. 
Anybody got any ideas or experience with what it might mean in simple terms? 
Had Air boost value too low on mine, truck wouldn’t pull and turbo boost gauage only went half way across. It was the silencer box that broke up inside…
andrewv8:
Had Air boost value too low on mine, truck wouldn’t pull and turbo boost gauage only went half way across. It was the silencer box that broke up inside…
Thank still got full boost on gauge, I do think there is a little loss in power, when it happened, but due to the low weight I pull, I reckon it would only be noticeable by me as the regular driver.
The exhaust corrosion has been picked up on inspections, I think it will be changed when it goes for test in November.
Volvo’s told Me that the new silencer box was £6,000. Didn’t notice too much when running empty, fully loaded and you could. Was down to 25mph climbing Windy hill Manchester bound, new box fitted goes up there at 45mph now…
Same here turbo guage only went two thirds . And sick on Hills found baffels had moved resticting gas flow . But got done under warranty phew £3700 +Labour
£6000 
let’s hope its something a bit more simple than that, I would say I still have full boost on the gauge.
muckles:
£6000
any truck from 2006 onwards and your looking at exaust prices ranging from £3000 too £9000. another haulier i know had 2 new silencers fitted too man trucks and had a bill for just short of £18000 including fitting. daf fitted a new silencer too the truck i drove 3 weeks ago and that cost £4200 including fitting, boss was having kittens as the trucks being sold at auction in a couple weeks time
i too have a 57 plate fh520 had the same code and your local dealer (and mine)had 8 attempts at it with no success. our fitter traced it to the ad blue pipes in the chassis behind the gearbox.as i think you are local to me and you will know of him try calling fish
eurotrans:
i too have a 57 plate fh520 had the same code and your local dealer (and mine)had 8 attempts at it with no success. our fitter traced it to the ad blue pipes in the chassis behind the gearbox.as i think you are local to me and you will know of him try calling fish
Hi thanks, I’ve seen the fault code before, I also get the engine symbol on the dash, book says its emissions fault, it gets turned off, but seems to return after a while. The first time it happened it cleared when I filled the adblue tank up, but doing this doesn’t seem to work now.
Just want to try and point the guys that looks after it in the right direction. They aren’t a Volvo dealer, but seem pretty switched on.
And although I’m based Norfolk the truck is based in tunbridge wells. Do you know what the problem with the pipes were or can you give me your fitters contact details. It’s was all a bit to cryptic for me. 
The Engine management light didn’t come on when silencer box packed up, have had a couple of Nox sesnsors go on it. Engine management light flashes and states it’ll ‘derate in 36 hrs’ then it’ll stop flashing after a while. Another few hours and Engine light flashes again ‘derate in 36 hrs’. Can go on for weeks, always got into the garage before it has derated…
sorry for the fog mate.Behind the gearbox mounted on a crossmember is a box in it the ad blue pipes meet.On my truck acouple had come loose and were leaking slightly. As i said our local dealer turned the light off 8 times and it was fine for about 2 to 3 hours until you come to a drag and on it came again.As the truck was under warranty we gained a new intercooler various senders and even a different silencer but none worked and eventually fish crawled over the truck for about 3 hours trying to find something loose (he is persistent) found these pipes, tightened them, and touch wood no problems since. Hope this helps mate
i would give you his number but he doesnt answer his phone but if you are in spooner row and not easily shocked pop in and see him
andrewv8:
The Engine management light didn’t come on when silencer box packed up, have had a couple of Nox sesnsors go on it. Engine management light flashes and states it’ll ‘derate in 36 hrs’ then it’ll stop flashing after a while. Another few hours and Engine light flashes again ‘derate in 36 hrs’. Can go on for weeks, always got into the garage before it has derated…
looking at the symptoms you’ve described and what Eurotrans has said. it’s looking more on the adblue side, and might be a better start point, cheaper option for a start, and when I get a chance I can get it into our car workshop and look round it myself. I also have to sort out the fuel tank breathers anyway, better I do things like that then send it to our local workshop, good and relatively cheap though they might be, a few hours of one of their guys to look round it soon adds up.
P.S. Sorry Eurotrans I forgot my manners in replying first time, and forgot to say Welcome to Trucknet.
Hi if the trucks based in T.wells I have a man who will sort out for you he is the mutts nuts on Volvos. Pm for details
Usually 3 pin plug on induction manifold after intercooler.3 wires feed ,earth and sensing.Also has induction air temp sensor built in. about 22 quid.dont mistake the one for induction air humidity sensor which is upstream of intercooler and turbo.
That fault code generally indicates the cat has moved inside, remove pipe look inside and it will become obvious if it has. ( check the honey comb part )
Got an update on this, they’ve replaced the Air boost sensor (or something with some of those words not got the bill in front of me ) and it seems to have sorted the problem, well for now anyway 
The sensor was about £150, plus getting it fitted, also went in for annual test at the same times so not sure how long fitting took.
Thanks for all the advice and help, no doubt I’ll post another thread when the next strange message appears on one of the trucks. @jwalker78 I’ve kept your mates details on file, could be useful to have an independent Volvo expert nearby.