Peugeot 307.my fuel gauge light is flashing and gauge not reading if i short either of the wires at sender gauge moves ,does this mean the fault is the sender or something else

The fuel level sender is located on the fuel pump hanger assembly. Sometimes the fuel pump, sender and hanger are all individually serviceable while other times the whole unit is replaced as a module assembly. The fuel level sender works by taking a 5 volt reference signal sent by the powertrain control module (PCM), modifying the voltage using resistance based on fuel level, then sending that signal back to the PCM. The PCM then reports the information to the body control module (BCM) so that the fuel level gauge in the instrument cluster can be adjusted accordingly. Fuel level senders are the most common failure for inaccurate fuel gauge readings. When the sender (or module assembly) is replaced, it's important to ensure the float is properly attached to the sender arm otherwise the resistance will not change with fuel level as designed. If this was done properly then there is likely a problem with the gauge or in the circuit between the level sender and the PCM. One easy way to test the circuit and gauge is to unplug the fuel pump; this creates an infinitely high resistance which should bottom out the gauge. Then, a jumper wire can be used to short the two sender wires (the smaller 2 of the 4 wires) to create a zero-resistance circuit which should top out the gauge. You can read more here: https://www.yourmechanic.com/article/symptoms-of-a-bad-or-failing-fuel-gauge-sender

SPECULATION only... because Peugeots were not
commercially imported to the USA in 2008... BUT

TYPICALLY you must empty & drop the
"GAS TANK" to access the sender unit
(fuel - pump)...

It is a big enough job where it is certainly reasonable
to lift your rear mats to LOOK & see if access is available
(through the car floor) with the FUEL TANK in place...

http://www.mister-auto.co.uk/en/sender-unit-fuel-tank/peugeot-207-wa-wc-1-6-hdi-90hp_v19352_g605.html

I did check a Peugeot FORUM and an UNANSWERED
question remains...

Does any one know how to remove the BIG NUT that
holds the fuel sender in place??
207 fuel sender removal Peugeot 307 forum Peugeot Central

My guess = BIG WRENCH (spanner)...
Sadly I have found no AMERICAN companies
that list significant PEUGEOT parts or tools from
1991 to 2009...

Hope this helps.

My suggestion would be to check the gage FIRST.

Carnac the Magnificent

Low or nil coolant
Broken or clogged coolant intake line

There might be but it is unlikely a fuel gauge is fused alone; usually if it is a fuse other things will stop working too but I suggest you are guided in this matter by your car handbook.

Problem is probably wiring and in particular the grounding of the fuel tank sender unit. It could be a faulty sender but they are usually quite reliable.

Test by disconnecting the wire from the sender unit at the fuel tank and short to a good ground and the gauge should read full. If the gauge wire is in a block with other wires it will be necessary to positively identify the gauge wire before testing.
If the gauge reads refit the wire and duplicate the ground wire to a known good ground. If the gauge still reads the fault is a bad ground to the tank sender unit and if it doesn't the sender unit itself is probably faulty.

If grounding the gauge wire does not produce a reading the fault is the wiring to the tank, the supply to the gauge or a problem with the gauge itself.

A constantly full fuel gauge is usually caused by a short circuit on the sensor wire. Check the wiring by isolating the wire as near as possible to the fuel gauge. Measure with an Ohm meter between the wire and earth, the reading should be more than 10 and less than about 200k. A short is indicated by a reading of around 0 Ohms, depending on the accuracy of your meter.
A second possibility is the sender unit in the fuel tank which could be faulty, and then finally, and only finally, the head gauge could be faulty.

Earth I am assuming is the GROUND for the tank or sending unit. Ground wires are usually black or green. This doesn't mean that it's not another color on your car, but black and green are the usual ground wire colors. Make sure that you have removed any rust that may be around the sending unit keeping it from being properly grounded to the tank. I'm not familiar with Peugeot, but I have seen many other similar problems with other vehicles sending units. If your gas tank is metal, make sure that it is grounded to the vehicles frame. Sometimes tanks depend on the mounting straps to ground the tank. They can rust and lose a good ground. You can also try manually grounding the sending unit to the tank or to the frame to see if that is the issue. If none of this works, it may be that your ground wire is broken somewhere between the sending unit and the dashboard which could be quite difficult to find. Good luck!

i would think that the fuel sender unit is not working , this is incorporated into the fuel pump , directly into the top of the fuel tank , i would get a mechanic to investigate as there are a few checks that can be made to determine where the fault lies before going ahead and changing the fuel sender

its 1 of 2 things.
1: the fuel is low, use a dip stick, if gauge reads ok.
2; or the tank sender is bad, but gauge reads wrong.
3: the guage wire is disconnected, cut or corroded connections.

Sounds like the fuel tank sender is no longer working. Its just a resistor on a rod and float set up. You will need to drop the tank out to get the sender out.

Sure there is!

DO THIS FIRST!!!
When you turn the key on, and the gauges and warning lights come to life, does the needle on the fuel gauge move a tiny bit? It should. If it does move a hair, this is a good sign your gauge is still good. If not, keep reading.

The gauges themselves are usually not at fault, but they can fail, of course. Usually, it's the sender or float that's the culprit. The assembly resides in the fuel tank in the module or unit that houses your fuel pump. Many customers (when faced with the cost of this tank job) will opt for waiting until the fuel pump goes bad, and replacing pump and sending unit together. However, there are obvious drawbacks to this!

ONE test you could do if you are good at driveway car work is this: Crawl under vehicle and find the bundle of wires (not tubes or lines) that goes up to the top of the fuel tank. Sometimes you can reach it through the rear wheel well. Follow this small group of wires up to wherever it plugs in to the pigtail coming out of the tank. THis could be on top of tank, or just outside the perimeter of the tank. Unplug this connection. Using a common 12 volt test lamp probe, ground the test lamp, turn the key to the "ON" position so dash lights up, and touch tester to each wire tip on the end not connected to the tank (engine side of wire harness.) Have someone watch the fuel gauge as you touch the leads one by one. The gauge should move when one of these is grounded thru the lite. Total deflection of the needle means your sender is at fault, not the gauge. BUt it's usually the sender, anyway. THey're cheap enough, but the labor on a tank job can vary from place to place.

Good luck, TT