C5X7 fault code 040A - Oil Gauge Fault

[Lynnzer]

The car showed a low oil message recently and I bought a few ltrs and without checking the actual level I poured about 2 litres in. Then when I did a check it was higher than the dipstick indicator. It's therefore likely that the level wasn't low to start with, or not low enough to give a warning message. The low oil level warning didn't clear even though it wasn't low.
As I was at the point where I was thinking about a service anyway, so I got an annual service done. On the report sheet it said that the oil level sensor was faulty. So I had this changed.
All that did was to change the warning message to one of "Oil Level Measurement Invalid."
I've just had it up to an auto electricians for a thorough engine management check. When the Snap On check was run, through all the possible codes, it came back with "Code 040A - Oil Gauge Fault - Not Characterized -Local". However the displayed fault message doesn't say Oil Gauge Fault.
The mechanic isn't able to clear the code as whatever is causing it needs to be fixed, but there's nothing that has any certainty to that. Oil Gauge Fault could be down to several things apparently so I'm stuck.
Has anyone got any experience of this that might help

[GiveMeABreak]

It's a known fault.

ALWAYS use the dipstick to check the oil amount on these engines and never rely on the electronic dash warning and just ignore the fault.

The reason is the oil level is measured up to a certain engine coolant temperature. Fault code F40A is recorded if the oil level has not been measured, as the temperature of the engine coolant was higher than the set threshold. Fault code F40A will be cleared from the list of faults in the BSI when the oil level is measured.

The fault will occur if the engine coolant temperature is 40°C or higher when it takes the oil level measurement.

[Paul-R]

What about the TSB to shorten the dipstick tube?

[GiveMeABreak]

...and just to clarify I'm assuming this is for your vehicle VIN ending 996 with the DW10CTED4 engine.

That being the case, Paul's reference to the oil dipstick guide tube modification only applies if you have faults F159 or B1818 coming up (with or without other faults). If so, then it won't affect the other issue, as if the dipstick tube mod is undertaken, the oil quantity should be re-checked and compensated for after the modification is made.

[Lynnzer]

That's the vehicle alright.
Love it but I know from past experience that there are unreconciled fault warnings on the range, or at least on the cars I've had, and it's so frustrating trying to get an answer.
Citroen Dealers, of course, won't assist by suggesting what the fault is indicative of, and the normal testing devices only really present a fault code that means very little most of the time.
The code and attributed message are 040A and Oil Level Measurement Invalid. That seems to me that the logical answer is that the method of checking the level, ie the sensor, is either not working or needs calibrating or something. The fault as shown on the printout from the test says it's an oil gauge fault, which says to me that the problem isn't with the sensor at all.
So if the oil gauge was changed is it likley to fix the problem?

[GiveMeABreak]

The technical bulletin states for Fault 'F40A' not 040A. There's no code being returned for 040A for the vehicle, so the mechanics are obviously not using Lexia Diagbox as there's no such fault code listed by Citroen. This is not uncommon for aftermarket tools that don't get the codes correct.

[Huskyxantia]

I get this code too & it dont bother me , as long as you know the oil level is correct on the stick , i do as ive just serviced the car 3 weeks ago , then your oil level is good & the engine has sufficient level needed , just go back to checking each week dip the stick check the level the old fashioned way i cant swear but these sensors are a pain in some respects even more when you can just stop being lazy and check yourself.