Am getting an error code on my TDV8 which is U0421.

When I look it up it refers to suspension control module A. My guess is that is one of the valve blocks and the letter A indicates the front one. Am I right or totally off the mark.

Help apprecaiated. Current cars
Range Rover Sport HSE TDV8
Range Rover TDV8 Vogue
Range Rover P38 Vogue
Range Rover CSK
Discovery 3 HSE

You need better diag gear...

The error code is missing two digits. As D_M alludes, the diagnostic kit you have isn't reading the whole of the code and thus not giving you the bit at the end that points to the problem. 2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed

And the lost comms code is not the root cause of your fault, that is a cascade fault

What are your symptoms?

I have a series of Fault codes which were read from a Snap on reader.
Codes I have relative to the faults (Have some relating to seatbelts and weight switch)
C1A13 Compressor Exhaust
U0434 Active Roll Control Module
U0421 Suspension Control Module A
U1A3B

I bought the car with the faults. The suspension is not rising evenly, The car flashes up with an error message telling me to stop the car and switch off the engine. I have changes the Active Roll Control Module but nothing changed.
I intended to take it to my local independent LR dealer to get it read properly however my other vehicles have problems and have nothing capable of towing the trailer.
When the fault codes were cleared it allowed access very temporarily to the height controller on the suspension. This allowed the back to be lifted but the front stayed down. This led me to thing it was the front valve block. Current cars
Range Rover Sport HSE TDV8
Range Rover TDV8 Vogue
Range Rover P38 Vogue
Range Rover CSK
Discovery 3 HSE

Focus on the C1A13

Thanks again Mikey.
So the most likely cause is a blockage to the compressor? Current cars
Range Rover Sport HSE TDV8
Range Rover TDV8 Vogue
Range Rover P38 Vogue
Range Rover CSK
Discovery 3 HSE

No, you have an issue with the exhaust valve

The final 2 digits of the code would narrow things down massively

Will need to get my own code reader as this seems to be a common problem I have with the codes. i.e.they are not specific.
Two more questions if you don't mind.

1. Where is the exhaust valve located? I guess this is something on the suspension pump.
2. Is it the came for the Disco 3? Current cars
Range Rover Sport HSE TDV8
Range Rover TDV8 Vogue
Range Rover P38 Vogue
Range Rover CSK
Discovery 3 HSE

Can only see one code beginning with C1A13 and that ends 64. Strange as slight difference in possible cause between 05-09 & 10-13 cars, first picture 05-09 second one 10-13 assume there must be some difference in design of system.

Click image to enlarge

Click image to enlarge

Thanks Col
It is a 2008 model, I have ordered a new compressor as I don't have an Hitachi one to swap over. All other parts I have got some hopefully I will have it cured very shortly. Current cars
Range Rover Sport HSE TDV8
Range Rover TDV8 Vogue
Range Rover P38 Vogue
Range Rover CSK
Discovery 3 HSE

Partial success giving big improvements.

Got the new compressor this afternoon and despite the grey weather decided to fit it. After a lot of cursing and swearing I managed to get the old one out and replacing the allen key bolts with normal hex head bolts refitted it and reassembled all the pipes and electrical fittings.

Then I started her up and the suspension went up and down as it should and is now sitting level which it never did since I got it. Now the suspension is working properly the computer isn't over riding it and putting the car into limp mode however the dash still comes up with the error message:

Suspension fault
Stop safely
Turn engine off.

I suspect that now relates to the Anti Roll Control Module fault, Am I correct? or is it Suspension Control Module A?

I don't have a computer so the other option is I need to clear the faults. Current cars
Range Rover Sport HSE TDV8
Range Rover TDV8 Vogue
Range Rover P38 Vogue
Range Rover CSK
Discovery 3 HSE

https://www.rrsport.co.uk/forum/topic57409.html

Mikey
The Anti Roll Control Module has been changed. Current cars
Range Rover Sport HSE TDV8
Range Rover TDV8 Vogue
Range Rover P38 Vogue
Range Rover CSK
Discovery 3 HSE

Perhaps...

Its time to down tools, pay for an hours diagnostics, and let a garage tackle it...