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What to do About OBD2 Codes?


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Hi all, new member.  If you recognise this post it's probably because I did post it on another forum but didn't get and responses so i thought I would see if this forum would be more forthcoming (now there's a challenge for you :) ).

I have my first Range Rover and my first experience of using an OBD2 reader.  I come from the days when the only things electrical  on a car were the lights and ignition!  Before going into the codes let me explain the situation ...

I bravely bought a 2005 very nice looking 4.2 supercharged L322 as a non-runner for what I think was a good price. Yes, I am a risk taker! image.gif.9c369eb0c8571edd2f4fad43bdbc2cce.gif I took a view that it would probably be a sensor or two or coils. The engine turns over and 'tries' to start as if only a few cylinders are firing but will not pick up. The last time I tried I stopped when it let out a large backfire through the intakes, I decided more of that would not do anything any good. image.gif.f8b40d7b8ce71a0caf69087a50d4190a.gif

I linked up the OBD2 reader with my phone and it returned the following ...




I think my first requirement is to get the engine running because if that's a no-no then so is the rest of the car. So my questions are ...

What is the difference between a code being "Confirmed" and "Pending"?

How do you go about tackling codes ... is there an order to them?  I have read that sometimes one code may be triggered by another code and fix that one and they are both fixed.  For example, I read that the U0300 fault can be caused by any sensor being at fault and throwing a dodgy reading to the ECM .

I wonder if I delete all codes (obviously I have a note of them) and then try and start the engine will the relevant 'non-starting' codes be recreated representing why it will not start? Or should I just plug on with the codes found?

I understand the codes such as P0102 etc but what are the codes "ECU:10" etc under them?

I have some MAF cleaner on a white van somewhere making it's way to me, try that first as it looks dirty/oily and hope it fixes P0102 and P0113.

I also read that U0403 can be caused by a slight drop in battery voltage and I mean slight, there are some reports of less than 12.6 volts causing this fault code to fire. The battery probably dropped well below that while repeatedly attempting to start the engine.

I have no idea how old the current codes are, should I clear all codes and then try and restart the engine and see what codes it refreshes?

Some guidance on how to proceed would be very welcome.

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Definitely do the above - also be aware that when you get a primary fault you will/may get secondary fault as a direct result of the primary fault - sometimes it is obvious what is going on sometimes not - I generally ignore communication faults if there are other major faults exist.  Also be aware that when a fault is fixed it may still continue to display until after one or two starts. Eg - I had alternator faults where everything lights up - fixed the alternator, cleared faults with my FCR and restarted - some faults continued until two starts.

On your list I would look at the IAT and MAF faults first, then see what remains - the others may be important but who knows.


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Also be aware that some recuring error codes may have nothing to do with your vehicle. My TD5 has a persistant logged error with the AC clutch, that could have something to do with thr fact I don't have air con!

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Thanks for all that guys ... so I'm on the right track thinking that I should clear the codes first, good.  I'm planning to clear the codes, disconnect the MAF/IAT (I hear the engine will run without the MAF/IAT connected a limp mode so I'm assuming it will also start in limp mode).  Then after, whether started or not, I will read any replacement codes it throws up.  Any work to be done can wait for when this cold win disappears!  :)

As another general question on codes it seems that there is a case to work on a "the car's running well so don't fix it ... ignore the code"?!  Do people work to that.

And finally, I recently came across this procedure to 'reset' the ECU and presumably force it back to some form of 'default' settings ...


Step 1

Open the fuse panel in the driver-side foot well, under the steering column, by pulling down on it with your fingers.

Step 2

Locate the fuse for the ECU using the fuse diagram on the underside of the fuse panel cover.

Step 3

Pull the fuse for the ECU using the fuse pullers in the fuse panel.

Step 4

Turn the ignition to the "On" position but don't crank the engine (it won't start anyway).

Wait five minutes and reinsert the fuse. The "Check Engine" light will blink, then shut off. This will indicate that your ECU has been reset.

Has anybody else come across this procedure and does it work/help?

Edited by firlandsfarm
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