Mitsubishi L200 engine won't rev

Depends on their equipment level,
First thing I'd do is check the CAS signal at the ECU with an oscilloscope.
The ECU has to "see" a square wave free from electrical noise.
If there's no signal at the ECU it's then retested at the CAS.
No signal there means a faulty CAS,
or the internal shaped steel disk that generates the signal chopping.
The crank pulley has to come off for this but it's a very rare fault.
Most likely is a cheap piece of crud CAS.
but the only way to test same is with a 'scope.
You can some idea of signal generation using a digital voltmeter,
Set it to millivolts and AC,
then DC
and crank it both times
numbers are not accurate but cranking it over "should" generate a reading of say 100 millivolts,
but this won't tell you if the signal is clean.
So 'scope it or buy a genuine CAS,
which wont help if it is a wiring short.
Only reading the signal on an oscilloscope would be definitive.

Further to my original post I have since been told my cheapest option is to get a second hand engine wiring loom and replace it myself. The only place I can find locally capable of diagnosing the fault accurately is a Mitsubishi dealership and I have been warned they will throw a load of replacement parts at until its fixed and charge me an arm and a leg for it! Is it a tricky job to replace the loom?

Horse****!
What if it's not the loom?
Bad advice!
Surely you have a local autospark equipped with an oscilloscope?
The whole point if diagnostic testing is you bring your car to me and I test it until I'm confident enough to put my money into repair.
That's the point where general mechanics fall down,
Just saying "it's might be the loom" is vague and unhelpful!
Now from my memory it's a hall effect CAS,
that means it has to be supplied with voltage.
first test.
check it at the CAS plug.
Now the CAS functions by a metal disk behind the crankshaft pulley that's fixed to the crank,
when the crank rotates this disk has notches cut out of the outer edge,
when one of these notches passes between the CAS the signal voltage changes from high to low.
then high to low and so on.
this produces a square shaped waveform on the 'scope screen.
Relatively simple.
And you just cant do diagnosing on a modern vehicle without an oscilloscope.
Without one you don't even know IF there's a signal,
if it's a clean signal and if the signal is getting to the ECU/PCM.
That just leaves guesswork,
Might as well stand ten feet away from the car and throw bundles of Twenty's at it in the hope that that will fix it,
That makes as much sense.
Where I'm sitting right now is original fault is lack of crank angle signal.
you fitted a new one,
nada,
leads me to believe there might have been nothing wrong with first CAS.
or the new cheap one,
Oh and That's a mistake.
Do you buy cheap coffee and like it?
Blech!
IT HAS TO BE 'SCOPED!!
Because it this point you and any other mechanic you've had checking it is just guessing.
We need to know absolutely without any doubt if there is any signal down at the CAS and if so is that signal getting to the ECU.
Then and only then can any reliable conclusions be drawn.
FIND A TECH WITH AN OSCILLOSCOPE!!!
Best guess would be a Bosch area specialist,
they're usually well equipped.
Or at a push try posting this on BBA REMAN forum and ask them if they can recommend a local tech to where you are.
Tread carefully on the forum though,
The guys who respond are shall I say a little tired with clown posting there looking for a "magic bullet" fix.
But for me I'm a little stunned that no one local to you has the knowledge or equipment to deal with this,
GET IT 'SCOPED!!!!

Ok try this test procedure from Mitsubishi workshop manual.
the CAS has a short wire harness going up the engine where it connect with the main engine harness,
unplug,
now testing the engine to ECU harness,
probing terminal #3 and earth should be system voltage i,e, battery.
probing terminal #2 and earth should be 4,6-5.4 v,
probing terminal #1 and earth should be continuity.
If it passes these test then the engine harness and ECU are good and your fault lies in the short connector,
the CAS,
or the steel reluctor disk behind the crank pulley.

Thanks for the advice mate I'll try that test and see how I get on. I'm not looking for a magic bullet fix, problem is where I live in rural Ireland the nearest guy I can find with the knowledge and equipment is an hour and a half drive away and he refused to come out and look at it, said I'd have to bring it to him which means paying a transporter for a 3 hour round trip before he even opens the bonnet. Looks like I might have to go down that route anyway. The joys of living in rip off Ireland!!

I have a 2007 L200 Elegance with exactly the same problem. The previous owner had the same problem and paid 750EURO for a specialist to diagnose a fuel problem!! His diagnosis was to replace the SCV. He said this solved his problem. The problem resurfaced for me in February 2015. I had it into a main dealer & 2 other independant mechanics and they can find 'No Problem'!!. After replacing several parts (including another genuine SCV), changing hoses, checking injectors, etc to no avail one mechanic suggested an intense fuel system cleaner - Hey Presto!! the problem went away (after appx 2 weeks driving with the cleaner in the fuel) UNTIL 2 weeks ago (nearly a year later) - the same problem has started again! If I can run the jeep for about 20kms (at appx 5kms per hour) the problem improves. All mechanics have told me it seems like a fuel problem but cannot give me a solution. I added the intense cleaner again this week so can let you know how that goes. I have a feeling there is another filter in the fuel line near the tank that is clogged but I can't find it.

Mate, did you find a solution? Got the same problem, 2007 L200 Elegance, ABS, traction lights comes on followed by the engine check light and no acceleration thereafter. Have replaced pressure control valve on the common rail + injectors cleaned + calibrated but the problem persists. Scanners showed fuel leak, low fuel pump pressure. Not the cause. Can you help, please.

Have you had a look at this similar problem:

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Guess I found a solution. Check the harness & the wires leading to the ECU. Check all the contact points for oxidization. Clean & re fix. Hopefully the problem will go away. Issue most likely is not mechanical but electrical. Hope this help / works.