Modic is a diagnostic tool for the UDM. It basically communicate with the
ECU (Electronic Control Unit) and draw out any errors that is store in the ECU.
Basically the ECU is the brain of the car. It control the ignition, fuel firing (injection), fuel pump based on various inputs from the car like engine throttle, O2 , crankshaft sensor, error.
Another things about the ECU, is that it remember your driving habit and also store limited amount of error with the car. like ABS, brake, transmission, throttle, O2 errors.
Nowadays, there are other diagnotic tool which emulate the Modic I & Modic II.
Some of them actually use laptop with certain software to do the job and with certain module can plug into other car makers. There are some people who sell reasonable price diagnostic tool which can read the error code from the ECU. You need to refer to the manual for the meaning of the error.
OK... back to topic.
If you have reading even when the tank is full, then you problem is due to one of the
following:-
1. The fuel sensor float is stuck at 3/4 mark.
2. The petrol needle at the Instrument cluster is offset.
1. If you have problem 2, you can further check out the following.
a) Fill the car to FULL and take note of the Mileage reading on the odometer.
b) Reset the trip meter to zero.
c) Drive around about 100 KM and observed how far the fuel needle dropped.
d) Repeat step c) until tank show almost "empty".
e) Fill the car to the FULL and note down how much litres goes into the tank.
From the above
1. if the petrol needle dropped gradually for every 100 KM, then your guage is working correctly to a certain extend.
2. If when you fill the tank to full and the amount of petrol is less than 60 litres,
then your fuel guage needle is offset. From your posting, you mentioned that it
take in only 50 litres. I think your needle is offset.
BTW, you did not mention whether the amber light warning light comes "ON"
when the tank is indicating empty. If the light did not comes "ON", this is another
confirmation that the needle is offset. You can confirmed this by driving around further with an "empty" tank until the amber warning comes ON.
Note: please keep a spare petrol can if you want to do the above test.
To rectify the above problem, fill the tank to full and drive home.
Open the instrument cluster and pull out the needle of the fuel guage.
"On" the ignition and put the needle back to FULL position.
