2004 euro 3 d5 2.4 limp mode
 

On start up the car will rev to red line. After around 10-15 seconds if you let it drop to idle the message power system urgent pops up and you can't rev beyond 3k revs and the warning triangle goes red. (If you don't let the revs fall, it will still rev between 3 and red after warning light come up?)
Cleaned pipes,and egr, they were horrible!
It had a recent alternator by previous owner, so have tried an original alternator - no joy
Turbo control valve solenoid changed with no luck.
No leaks in the vacuum system
Smoke tested inlet and other pipes no leaks
Cleaned map and maf
Cleaned and tested tcv - functions fine.
Battery is fine.
Basic reader errors
p0236 - atmospheric pressure sensor
p0244 - ?
p0480 -cooling fan relay
p0102 - maf
p0571 - brake pedal sensor
p0244 - throttle unit potentiometer
Would it be worth changing or testing (how) any of the above?

It's just weird that it can rev up fully, but I assume the ECU thinks that's you shouldn't because something's not right?

Don't know where to go now - any advice would be great.
Cheers

basic code readers are of little use on volvos you need vida or any other quality diagnostic tool anything else is just guessing p codes are just generic pointers that include no details..

As he said it needs to go on some Volvo or Volvo compatible gear.

These symptoms are a first for me - never ever heard of a [electronically managed] Volvo engine revving out of control, with the exception of diesel runaway when the turbo leaks oil into the inlet tract, but you would have a lot of smoke from the exhaust if that was the case.

Notice a throttle sensor error but I'd say that's unlikely the cause as Volvo cars have redundant sensors on the throttle - one digital and one analogue circuit. Almost aircraft levels of redundancy.

However in the absence of an obvious cause, you can't really rule anything out...

I'd disconnect the throttle sensor, i *think* the car should start but just tick over. I'd also try reading sensor values, which you should be able to do with a basic diagnostic, the MAF, APS, TPS and Brake pedal sensor - with the ignition on but engine not started.

And finally, don't buy any new parts until you've got a firm diagnosis, poke and hope substitution in the absence of diagnosis and/or experience will just empty your wallet on these cars. Spending £50-£80 to get it on proper gear will in 8 out of 10 cases tell you exactly what the problem is.

When it doesn’t make sense and you haven’t used Vida you need to try Vida. Hopefully it’ll point you to an easy fix. After that specialist diagnostics garage time but I would bet Vida will be most helpful. It’s an arse of a system really but once you have it running it works well.

I think what he means is that when you start the car it will allow you to rev normally and up to the redline, it's when you allow the revs to drop to idle it then won't rev.

To add to the good advice already given, I'd deal with the alternator problem first, as the electronics on these models are known to throw spurious errors when there are poor voltage conditions. Once that's sorted and you've cleared down existing DTCs, then what remains/recurs is 'real' and can be trusted as the basis of further diagnosis, if any is required.

That's the meaning of the "Power System Urgent" message, the CEM thinks the charging system has a fault. Possible causes may be that you have the wrong alternator fitted, or issues with the alternator wiring (either the power connections, including grounding leads) or the smaller connector which brings digital signaling into the alternator.

When I had my XC90 I encountered occasional limp mode which I eventually cured by changing the air pressure sensor that sits, on the Euro4 D5, on the nearside of the intercooler. Cost me about £30 for Bosch part from carparts4less, but collected from ECP. Very easy to change.