1999 HSK, Petrol
I had been having issues with a "FAULTY FUEL SENDER" indication on the message center display accompanied by fuel needle plunging
to zero and low fuel indicator light being illuminated.
This only happened after a fill up, so full tank. It got good when fuel was below 3/4 tank and was correct to empty.
I assumed that it was a sender with a worn track at the top end, so I swapped in a fully tested, known good fuel pump and sender assembly.
This seemed to fix the issue straight away! The old sender indeed had bad sections on the track at the top end, and about the 3/4 mark.
Bench testing with ohm meter confirmed this.
Now, however, I am getting a "FUEL GAUGE FAULT" indication on the message center, along with the needle plunge and low fuel light indication.
When ignition is switched on, the gauge reads correctly. after starting, and idling a few seconds it faults out. I noticed that a few times when it stayed accurate
for a bit, that pressing the brake would fault it out (Bad earth somewhere?)
Plugged in Nano, and looked at fuel sender values. Got a 36 and this dropped to a 26 when brake was pressed.........And went as low as 8.
I cannot seem to find my guide to the Nano that indicates what these readings should be?
Comparing to my 2002, the fuel sender readings on it stay solid at 69 when I press brake....(It has less fuel, so I would expect different number)
Any hot tips as to where to start looking? I have confirmed earths under the bonnet are good, so I suppose it's under the dash next.
I've seen FUEL GAUGE FAULT come up on the dash before, accompanied by the fuel gauge dropping to zero and the low fuel warning light coming on. However, that was due to wear on the track at a certain point that coincided with the amount of fuel I normally keep in the car. As the car runs on Propane, the petrol is purely a get you home option so the fuel gauge very rarely moved resulting in the wear. Replacing the fuel pump module cured it. About the only other thing I did was give the plug to it a squirt of contact cleaner before plugging it in.
Changing when pressing the brake pedal would suggest, as you rightly say, a bad ground connection. Fuel gauge and brake lights don't share a supply so it can't be a fuse but on a LHD car, both the ABS ECU and the fuel pump/sender assembly go to E0559 ground point. Your task is now to find out where E0559 is.....
Thanks Gilbert!
Turns out that E0559 is the one on the wing next to the coolant expansion bottle.
Clean and tight, but wire brushed just in case.
Also checked C1289 the 20 pin plug on BECM. Clean and tight. Checked all the plugs on the front, since I was in there.
All looked good, so no moisture getting to the BECM.
So, as I had done the "Surgically cut flap" procedure for the fuel pump (I have only gravel surfaces to work on at
present.....Shop floor coming soon.) It only took a minute to remove sealant and access the pump (Luxury!)
I opened the flap, and checked the pump connection. Clean.
Next I took the old fuel pump and plugged it in to see if the old problem was still the same.
Yep! gauge read correctly and exhibited all the symptoms that I expected from a known worn out sender.
Plugged the "New" pump back in, and, with key in Pos II gauge reads full, as I would expect, as tank is full......
So, start engine and within 5-10 seconds needle sails down to empty and I get "Gauge Fault" message.
The pump and sender was very recently in my 02 and worked flawlessly. I suppose I could have damaged it in the transplant, but took great care not to.
Odd that it thinks Gauge is at fault when it seems to be a sender issue?
Further thoughts welcome!
I am going to take it for a drive today to get the tank down a bit and see what happens.
Probably because FUEL GAUGE SENDER UNIT FAULT is too long to fit in the massage centre.... For the average owner, they wouldn't know what the gauge sender is, all he'd know is the fuel gauge isn't working correctly.
Not sure if relevant but the brake light switch takes power from the single connector on the back of the BeCM, the one that you access from the rear footwell. The HEVAC backlighting is on the same feed so if the HEVAC dims when you put the brakes on, that is suspect. There's one caveat to that. It is like that on a GEMS and I was recently told that a Thor BeCM will work in a GEMS but not the other way round. I thought they weren't interchangeable but this came from Les at Classic Rides North Wales who supplies the aftermarket keys.
FUEL GAUGE FAULT appeared every now then on mine a few months back. Turns outs the alternator was just about to give up.
New alternator, not seen since..
With the old sender, it did indeed say "FUEL SENDER FAULT"
And, it was indeed faulty.
I had my run to bring down the fuel level, and no change,
So, I went to the boat and got my good ohm meter......
I found the "New" sender reading 39 ohms.
So, got my trusty resistor substitution wheel, and clipped it to the sender wires.
For the resistance I applied to the wires at the fuel tank plug, I got these results:
47 ohms- Full
100 ohms- 1/2
150 ohms- 3/8
220 ohms 1/8
330 ohms- Empty
This is correct according to an old post on the dark side by Marty, so you know its good data!
Looking like the sender got upset during it's transplant.
Next, I will obviously need to pull it back out to see what I did to upset it!
On the subject of BECM compatibility, At least for NAS spec, they seem to be reverse compatible.
Long ago, I had Scotty (Remember him!?) unlock and clone one from my 95 parts car to work in my 02, which it has been doing just fine......
Not sure, but he may have done a firmware update as well????
Thanks, once again for the help!
I will report back when I find out how I managed to destroy a perfectly good sender.