Crazy Electronics And Fuel Gauge

[Guest Dan Slatford]

Something extremely strange happened today, and I wonder if anyone else has experienced same or similar - or knows a thing or two about the fuel sender?

 

I have a 2.2HDi 2001. Driving along today, for a brief moment the whole dash went crazy - lights off, relays chattering, beeping galore. Almost as soon as I realised something quite major just happened, everything righted itself - except the service light was on, the door lock LED lit, and the display moaning about low fuel with gauge on empty. There was a few tens of miles above the reserve to go yet.

 

Pulled over, switched off and opened / closed door, locked / unlocked. Everything seemed fine except the fuel gauge, still showing empty. Got home, tried pulling the battery for half an hour, but still the same. Put 20 litres of fuel in, and the gauge then shot to half full.

 

Possibly correct given there was some fuel in the tank already, and it shouldn't yet have been showing the low warning. Possibly over-reporting. Worrying all the same.

 

Has anyone else had weirdness like this? In the few months I've had the car, I haven't seen any major electronic problems. (Every so often it moans about braking fault on starting, but re-starting resumes normality)

 

I'm not sure if I'm looking at a faulty fuel sender (isn't that part of the pump on these? any idea how much for a new one?), faulty COM2000, wiring issue or other.

[72dudes]

I also have a 2001 2.2 HDi but have not experienced anything as weird as this. I have however had two occasions when the fuel gauge showed 3/4 full when I'd just brimmed the tank, and another time it got stuck on 1/3 when there was under a 1/4 of a tank in.

 

The first time I was worried but kfk assured me it would correct itself - it did next time I filled up each time.

Has the Service light gone out yet? If not, I would be willing to guess that it will disappear in the next few days (or 6 unlock/start cycles).

 

I can't help you with the cause or potential cost I'm afraid, and although I don't like the sound of the relays clicking and the beeps, you might at least take some comfort from the fact that the fuel gauge thing is not uncommon!

[Randombloke]

I can't help you with the cause or potential cost I'm afraid, and although I don't like the sound of the relays clicking and the beeps, you might at least take some comfort from the fact that the fuel gauge thing is not uncommon!

 

Range forecast on fuel will not recognise anything under 10 litres AFAIK.

 

I don't trust the reserve indicator. It goes blank with about 25 miles predicted range.

 

Electrics failure:

 

You will need to look for a damaged cable or a loose connection. Be 100% sure that all cables are secure and all connectors are tight. Check the main +ve and -ve straps from the battery. Having properly disconnected the battery, be sure all nuts are done up tight and there is no corrosion.

 

Check the condition of the battery. If you have ANY doubt replace it. If the battery is not very healthy and capable of absorbing spikes from the starter motor and hydraulic pump, then the many sensors and ECUs will get a supply spike which will banjax them.

 

Lastly, with the engine running, maybe consider lightly tapping each fuse in the glove box with the plastic end of a screwdriver. With an assistant helping do the same in the engine bay.

 

Put a meter or plug in indicator in the cigarette lighter and read the voltage with engine on and off. Post here?

[Guest JeffersanhisC5]

I have the 2001 2.0 HDI and have experienced the exact same problem you are describing on about 3 seperate occassions, once at night when all the headlights went out momentarily. However i have owned the car for 2 years and after checking out all the usual suspects i have put it down to an annoying gliche in the electrical system that appears to be a characteristic of some of the earlier models. After all there have been no long term consequences and the system appears to right itself quickly so i just live with it.

Other sporadic messages include (in my case anyway) Passenger airbag fault (about 5 times) and top up engine oil (about 6 times) even when full. Hopefully its not a pre cursor to something more serious and just an annoyance, after all the C5 is not renound for its superior electrics.

[Guest Dan Slatford]

Well, so far it hasn't come back. I am wondering if it'll reoccur when the fuel level nears the reserve again.

 

Haven't measured battery voltage while running recently, but I had earlier in the year and no problems then. The engine starts within milliseconds of turning the key, I'd have thought if the battery was "on its way out" it wouldn't supply all the immense current needed to start the engine so quickly? I'm rather loathe to spend out on a new battery when I can't demonstrate anything wrong with the present one. I did clean and grease the terminals.

 

I looked under the fuel sender/pump cover too. Curiously the cover (under the rear seat) was loose - not properly clipped in. There's also some sort of control box secured to the underside of this. I can't even guess as to what this is for, but the whole thing was free to move around, if only slightly. Given that there appeared to be an electrical fault even briefly, and the connection with the fuel sender - I wonder if this unit and maybe a chance bad connection has anything to do with it?

 

There seems to be control units stashed everywhere in the C5!

 

In the 9 months I've had the car, I had a warning about the passenger aigbag once - just the other day, in fact. The occurrence of the ABS FAULT on start-up has increased though, to a few times a week. Re-starting the engine makes it go away (and ABS / EBS does work!) so that's more a mild annoyance at the moment than a real worry.