With the increasing complexity of cars it is nearly impossible to perform even a basic fault diagnostics without some way of querying the information stored in the car's ECU.

The information you can get from the OBD system depends on the car, generally the newer and more complex the car, the more info you can "capture".

If you've ever had the MIL (Malfunction Indicator Light or CEL (Check Engine Light) come on, your engine is trying to tell you something, 9 times out of 10 it is an emissions based problem as the standard was brought in to notify the driver of a possible increase of emissions. e.g. if a Lambda sensor is failing, or even certain gearbox issues will cause an increase in emissions that will warrant a code.

The other great tool is that you can see real time data from the various sensors, air temp, fuel temp, coolant temp, air pressure, fuel pressure, O2 readings pre and post cat etc. This is all great if you think a dodgy sensor is causing rough running etc, because you will generally see that something is immediately wrong.

Thankfully all cars from 1996 now have a plug n play OBDII port. Your Range Rover has it's OBD port in the coin tray beneath and to the right of the steering wheel, behind a black flap (looks like a scart socket)

There are 3 main ways of reading error codes:

Main Dealer - generally expensive, he will plug his computer into the car, read the codes, reset the codes and can also query sensor data.

Handheld Code Reader - A device with an LCD display that will give you the error code, and will usually allow you to clear it, the more expensive ones have code description too, so you will get the code and a brief description of the fault. Usually cant read sensor data.



USB OBD Readers - These in my opinion are far superior to the handheld versions as they can read the sensor data. They generally all have decent bundled software that will give you a detailed analysis of all available systems. They are also generally the cheapest, but require a laptop to plug into. There are also Bluetooth versions of the same that will work with pocket PC's etc



When buying it is important that you get the right one, generally the vendor selling will list the cars they will work with, but the only ones that are odd are the ones that work with VW/Skoda as they use a different protocol (some will automatically work with both) where as the EU/US cars use CAN Bus

The USB readers vary in price, but they all generally do the same thing. I would expect to pay around £30 from the likes of eBay and it will probably come from Hong Kong in 10 days. The handheld ones can cost between 70 and 150 depending on functionality.

Either way, I wouldn't be without one. It is permanently in the box in the boot of my car with other essentials, as my laptop is generally always with me, if I get a code I can read it immediately to decide whether it is safe to continue driving or whether I should be towed home.

Some Screenshots from my P38:

Click image to enlarge

Admin note: this post has had its images recovered from a money grabbing photo hosting site and reinstated

Can I ask which OBD you went for? Also, I notice you had data from your P38, have you tried it on your L322?
Cheers,
Steve Steve

Main car : FFRR L405 Vogue SDV8
Other car : Vauxhall Lotus Carlton
Past cars : FFRR L322 Vogue TD6 SE (Sept 2006 MY07) ; LandCruiser SWB ; 4-Runner ; Supras; XJS V12 LeMans

Dan are you only interested in reading the data rather than reading and resetting the DTC's

Thanks for posting this Dan. Following my recent problems you said to get one and I have kept meaning to ask for more info. Do you have an ebay link? Having got the kit how do you know what to do with it and what it is telling you. Seams a long way from holding a screw driver to the block and your ear. letters not necessarily in the right order

I'm very tempted to get the Bearmach one

RRVSE wrote:

Can I ask which OBD you went for? Also, I notice you had data from your P38, have you tried it on your L322?
Cheers,
Steve

Steve,

I went for one very similar to This . (eBay links stop working after a while, just search for "USB OBD")

Yes I have used it on the L322, quite a few times when I was tracking down and resetting codes due to my leaky PCV system, like I said, I wouldnt be without it now. 

Dixy wrote:

Having got the kit how do you know what to do with it and what it is telling you. Seams a long way from holding a screw driver to the block and your ear.

Any one you buy should come with good instructions, generally they are fairly simple. DigiMoto I find has the best user interface.

Sometimes you have to assign the com port to the USB manually (usually if you plug it into a different port than the one you installed it on) but this isn’t as daunting as it sounds! 

Great post Dan, thanks for clearing the mist! Discovery 4 HSE
1998 110 TUM HS FFR Hard Top XD WOLF
1982 Series 3 Hard Top

*Gone:L462 D5 HSE LUX, L663 Defender 110 HSE, Discovery 3 HSE, 2014MY Range Rover Sport 5.0 Supercharged AB Dynamic; L405 Exec Vogue SE 4.4, 5.0 Supercharged Autobiography, Defender TDCi XS CSW, Defender TD5 HT, Vogue SE TDV8, Vogue TD6, RRSport SC 4.2V8, Classic 3.9 Vogue Auto, Land Rover Series 3 SWB

ken wrote:

Dan are you only interested in reading the data rather than reading and resetting the DTC's

Ken,

As any OBD Reader's main purpose is to read and reset the Error Codes or Diagnostics Trouble Codes that is my main reason for having one, but as I also wanted to be able to read extended data that's why I bought and would recommend the USB one.

Dan 

its good having an unbiased view on this subject if you have read the D3 thread you know what I mean

Any thoughts on the bearmach one

Which Bearmach one would that be? U got a link? 

Cheers Dan,
They're a lot cheaper than I thought they'd be. The ebay one being @£12 with of course @£13 shipping, but £25's not bad. Thanks for your help,
Steve Steve

Main car : FFRR L405 Vogue SDV8
Other car : Vauxhall Lotus Carlton
Past cars : FFRR L322 Vogue TD6 SE (Sept 2006 MY07) ; LandCruiser SWB ; 4-Runner ; Supras; XJS V12 LeMans

The price has dropped then for the USB ones. Some of the ELM chip based USB units were upwards of £80 only last year and the software (usually shareware) was partially in Hungarian.

I know the Chinese were getting in on the act and things were getting cheaper, but £12 is excellent.

Lets face it, they've always been made in China for 50p its just we've been paying a disgusting markup! I think I paid about £25 for my ELM327? from China. 

Hi,
do any codereaders do BMW and LRcars?
I have a BMWat the moment but plan on a FFRR in the not too distant future.
Ed